Mark official release

Revert use of boost::container::small_vector in the evaluator

.editorconfig

@@ -17,7 +17,7 @@ indent_style = space
 indent_size = 2
 
 # Match c++/shell/perl, set indent to spaces with width of four
-[*.{hpp,cc,hh,sh,pl}]
+[*.{hpp,cc,hh,sh,pl,xs}]
 indent_style = space
 indent_size = 4
 

.github/ISSUE_TEMPLATE/missing_documentation.md

@@ -11,6 +11,10 @@ assignees: ''
 
 <!-- describe your problem -->
 
+## Proposal
+
+<!-- propose a solution -->
+
 ## Checklist
 
 <!-- make sure this issue is not redundant or obsolete -->
@@ -22,10 +26,6 @@ assignees: ''
 [source]: https://github.com/NixOS/nix/tree/master/doc/manual/src
 [open documentation issues and pull requests]: https://github.com/NixOS/nix/labels/documentation
 
-## Proposal
-
-<!-- propose a solution -->
-
 ## Priorities
 
 Add :+1: to [issues you find important](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc).

.github/PULL_REQUEST_TEMPLATE.md

@@ -10,24 +10,6 @@
 
 <!-- Large change: Provide instructions to reviewers how to read the diff. -->
 
-# Checklist for maintainers
-
-<!-- Contributors: please leave this as is -->
-
-Maintainers: tick if completed or explain if not relevant
-
- - [ ] agreed on idea
- - [ ] agreed on implementation strategy
- - [ ] tests, as appropriate
-   - functional tests - `tests/**.sh`
-   - unit tests - `src/*/tests`
-   - integration tests - `tests/nixos/*`
- - [ ] documentation in the manual
- - [ ] documentation in the internal API docs
- - [ ] code and comments are self-explanatory
- - [ ] commit message explains why the change was made
- - [ ] new feature or incompatible change: updated release notes
-
 # Priorities
 
 Add :+1: to [pull requests you find important](https://github.com/NixOS/nix/pulls?q=is%3Aopen+sort%3Areactions-%2B1-desc).

.github/labeler.yml

@@ -16,8 +16,8 @@
 "new-cli":
   - src/nix/**/*
 
-"tests":
+"with-tests":
   # Unit tests
   - src/*/tests/**/*
   # Functional and integration tests
-  - tests/**/*
+  - tests/functional/**/*

.github/workflows/backport.yml

@@ -14,14 +14,14 @@ jobs:
     if: github.repository_owner == 'NixOS' && github.event.pull_request.merged == true && (github.event_name != 'labeled' || startsWith('backport', github.event.label.name))
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           ref: ${{ github.event.pull_request.head.sha }}
           # required to find all branches
           fetch-depth: 0
       - name: Create backport PRs
         # should be kept in sync with `version`
-        uses: zeebe-io/backport-action@v1.3.0
+        uses: zeebe-io/backport-action@v2.1.1
         with:
           # Config README: https://github.com/zeebe-io/backport-action#backport-action
           github_token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/ci.yml

@@ -11,15 +11,16 @@ jobs:
   tests:
     needs: [check_secrets]
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v21
+    - uses: cachix/install-nix-action@v23
       with:
         # The sandbox would otherwise be disabled by default on Darwin
         extra_nix_config: "sandbox = true"
@@ -57,11 +58,11 @@ jobs:
     outputs:
       installerURL: ${{ steps.prepare-installer.outputs.installerURL }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 0
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v21
+    - uses: cachix/install-nix-action@v23
       with:
         install_url: https://releases.nixos.org/nix/nix-2.13.3/install
     - uses: cachix/cachix-action@v12
@@ -76,13 +77,14 @@ jobs:
     needs: [installer, check_secrets]
     if: github.event_name == 'push' && needs.check_secrets.outputs.cachix == 'true'
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v21
+    - uses: cachix/install-nix-action@v23
       with:
         install_url: '${{needs.installer.outputs.installerURL}}'
         install_options: "--tarball-url-prefix https://${{ env.CACHIX_NAME }}.cachix.org/serve"
@@ -99,6 +101,9 @@ jobs:
 
   docker_push_image:
     needs: [check_secrets, tests]
+    permissions:
+      contents: read
+      packages: write
     if: >-
       github.event_name == 'push' &&
       github.ref_name == 'master' &&
@@ -106,10 +111,10 @@ jobs:
       needs.check_secrets.outputs.docker == 'true'
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v21
+    - uses: cachix/install-nix-action@v23
       with:
         install_url: https://releases.nixos.org/nix/nix-2.13.3/install
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
@@ -124,10 +129,30 @@ jobs:
     - run: docker load -i ./result/image.tar.gz
     - run: docker tag nix:$NIX_VERSION nixos/nix:$NIX_VERSION
     - run: docker tag nix:$NIX_VERSION nixos/nix:master
+    # We'll deploy the newly built image to both Docker Hub and Github Container Registry.
+    #
+    # Push to Docker Hub first
     - name: Login to Docker Hub
-      uses: docker/login-action@v2
+      uses: docker/login-action@v3
       with:
         username: ${{ secrets.DOCKERHUB_USERNAME }}
         password: ${{ secrets.DOCKERHUB_TOKEN }}
     - run: docker push nixos/nix:$NIX_VERSION
     - run: docker push nixos/nix:master
+    # Push to GitHub Container Registry as well
+    - name: Login to GitHub Container Registry
+      uses: docker/login-action@v3
+      with:
+        registry: ghcr.io
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+    - name: Push image
+      run: |
+        IMAGE_ID=ghcr.io/${{ github.repository_owner }}/nix
+        # Change all uppercase to lowercase
+        IMAGE_ID=$(echo $IMAGE_ID | tr '[A-Z]' '[a-z]')
+
+        docker tag nix:$NIX_VERSION $IMAGE_ID:$NIX_VERSION
+        docker tag nix:$NIX_VERSION $IMAGE_ID:master
+        docker push $IMAGE_ID:$NIX_VERSION
+        docker push $IMAGE_ID:master

.github/workflows/hydra_status.yml

@@ -13,7 +13,7 @@ jobs:
     if: github.repository_owner == 'NixOS'
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 0
     - run: bash scripts/check-hydra-status.sh

.github/workflows/labels.yml

@@ -21,4 +21,4 @@ jobs:
     - uses: actions/labeler@v4
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
-        sync-labels: true
+        sync-labels: false

.gitignore

@@ -18,7 +18,7 @@ perl/Makefile.config
 /doc/manual/generated/*
 /doc/manual/nix.json
 /doc/manual/conf-file.json
-/doc/manual/builtins.json
+/doc/manual/language.json
 /doc/manual/xp-features.json
 /doc/manual/src/SUMMARY.md
 /doc/manual/src/command-ref/new-cli
@@ -26,6 +26,7 @@ perl/Makefile.config
 /doc/manual/src/command-ref/experimental-features-shortlist.md
 /doc/manual/src/contributing/experimental-feature-descriptions.md
 /doc/manual/src/language/builtins.md
+/doc/manual/src/language/builtin-constants.md
 
 # /scripts/
 /scripts/nix-profile.sh
@@ -78,22 +79,24 @@ perl/Makefile.config
 
 /src/build-remote/build-remote
 
-# /tests/
-/tests/test-tmp
-/tests/common/vars-and-functions.sh
-/tests/result*
-/tests/restricted-innocent
-/tests/shell
-/tests/shell.drv
-/tests/config.nix
-/tests/ca/config.nix
-/tests/dyn-drv/config.nix
-/tests/repl-result-out
+# /tests/functional/
+/tests/functional/test-tmp
+/tests/functional/common/vars-and-functions.sh
+/tests/functional/result*
+/tests/functional/restricted-innocent
+/tests/functional/shell
+/tests/functional/shell.drv
+/tests/functional/config.nix
+/tests/functional/ca/config.nix
+/tests/functional/dyn-drv/config.nix
+/tests/functional/repl-result-out
+/tests/functional/test-libstoreconsumer/test-libstoreconsumer
 
-# /tests/lang/
-/tests/lang/*.out
-/tests/lang/*.out.xml
-/tests/lang/*.ast
+# /tests/functional/lang/
+/tests/functional/lang/*.out
+/tests/functional/lang/*.out.xml
+/tests/functional/lang/*.err
+/tests/functional/lang/*.ast
 
 /perl/lib/Nix/Config.pm
 /perl/lib/Nix/Store.cc
@@ -135,4 +138,9 @@ nix-rust/target
 
 result
 
+# IDE
 .vscode/
+.idea/
+
+# clangd and possibly more
+.cache/

.version

@@ -1 +1 @@
-2.16.0
+2.19.0

CONTRIBUTING.md

@@ -5,7 +5,6 @@ We appreciate your support.
 
 Reading and following these guidelines will help us make the contribution process easy and effective for everyone involved.
 
-
 ## Report a bug
 
 1. Check on the [GitHub issue tracker](https://github.com/NixOS/nix/issues) if your bug was already reported.
@@ -25,28 +24,51 @@ Check out the [security policy](https://github.com/NixOS/nix/security/policy).
 
 ## Making changes to Nix
 
-1. Check for [pull requests](https://github.com/NixOS/nix/pulls) that might already cover the contribution you are about to make.
-   There are many open pull requests that might already do what you intent to work on.
-   You can use [labels](https://github.com/NixOS/nix/labels) to filter for relevant topics.
+1. Search for related issues that cover what you're going to work on.
+   It could help to mention there that you will work on the issue.
 
-2. Search for related issues that cover what you're going to work on. It could help to mention there that you will work on the issue.
-   Pull requests addressing issues labeled ["idea approved"](https://github.com/NixOS/nix/labels/idea%20approved) are especially welcomed by maintainers and will receive prioritised review.
+   Issues labeled [good first issue](https://github.com/NixOS/nix/labels/good%20first%20issue) should be relatively easy to fix and are likely to get merged quickly.
+   Pull requests addressing issues labeled [idea approved](https://github.com/NixOS/nix/labels/idea%20approved) or [RFC](https://github.com/NixOS/nix/labels/RFC) are especially welcomed by maintainers and will receive prioritised review.
+
+   If you are proficient with C++, addressing one of the [popular issues](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc) will be highly appreciated by maintainers and Nix users all over the world.
+   For far-reaching changes, please investigate possible blockers and design implications, and coordinate with maintainers before investing too much time in writing code that may not end up getting merged.
+
+   If there is no relevant issue yet and you're not sure whether your change is likely to be accepted, [open an issue](https://github.com/NixOS/nix/issues/new/choose) yourself.
+
+2. Check for [pull requests](https://github.com/NixOS/nix/pulls) that might already cover the contribution you are about to make.
+   There are many open pull requests that might already do what you intend to work on.
+   You can use [labels](https://github.com/NixOS/nix/labels) to filter for relevant topics.
 
 3. Check the [Nix reference manual](https://nixos.org/manual/nix/unstable/contributing/hacking.html) for information on building Nix and running its tests.
 
    For contributions to the command line interface, please check the [CLI guidelines](https://nixos.org/manual/nix/unstable/contributing/cli-guideline.html).
 
-4. Make your changes!
+4. Make your change!
 
 5. [Create a pull request](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request) for your changes.
-   * [Mark the pull request as draft](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/changing-the-stage-of-a-pull-request) if you're not done with the changes.
+   * Clearly explain the problem that you're solving.
+
+     Link related issues to inform interested parties and future contributors about your change.
+     If your pull request closes one or multiple issues, mention that in the description using `Closes: #<number>`, as it will then happen automatically when your change is merged.
    * Make sure to have [a clean history of commits on your branch by using rebase](https://www.digitalocean.com/community/tutorials/how-to-rebase-and-update-a-pull-request).
-   * Link related issues in your pull request to inform interested parties and future contributors about your change.
-     If your pull request closes one or multiple issues, note that in the description using `Closes: #<number>`, as it will then happen automatically when your change is merged.
+   * [Mark the pull request as draft](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/changing-the-stage-of-a-pull-request) if you're not done with the changes.
 
 6. Do not expect your pull request to be reviewed immediately.
    Nix maintainers follow a [structured process for reviews and design decisions](https://github.com/NixOS/nix/tree/master/maintainers#project-board-protocol), which may or may not prioritise your work.
 
+   Following this checklist will make the process smoother for everyone:
+
+   - [ ] Fixes an [idea approved](https://github.com/NixOS/nix/labels/idea%20approved) issue
+   - [ ] Tests, as appropriate:
+     - Functional tests – [`tests/functional/**.sh`](./tests/functional)
+     - Unit tests – [`src/*/tests`](./src/)
+     - Integration tests – [`tests/nixos/*`](./tests/nixos)
+   - [ ] User documentation in the [manual](..doc/manual/src)
+   - [ ] API documentation in header files
+   - [ ] Code and comments are self-explanatory
+   - [ ] Commit message explains **why** the change was made
+   - [ ] New feature or incompatible change: updated [release notes](./doc/manual/src/release-notes/rl-next.md)
+
 7. If you need additional feedback or help to getting pull request into shape, ask other contributors using [@mentions](https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#mentioning-people-and-teams).
 
 ## Making changes to the Nix manual

Makefile

@@ -1,3 +1,7 @@
+-include Makefile.config
+clean-files += Makefile.config
+
+ifeq ($(ENABLE_BUILD), yes)
 makefiles = \
   mk/precompiled-headers.mk \
   local.mk \
@@ -18,16 +22,23 @@ makefiles = \
   misc/upstart/local.mk \
   doc/manual/local.mk \
   doc/internal-api/local.mk
+endif
 
--include Makefile.config
-
-ifeq ($(tests), yes)
+ifeq ($(ENABLE_BUILD)_$(ENABLE_TESTS), yes_yes)
+UNIT_TEST_ENV = _NIX_TEST_UNIT_DATA=unit-test-data
 makefiles += \
   src/libutil/tests/local.mk \
   src/libstore/tests/local.mk \
-  src/libexpr/tests/local.mk \
-  tests/local.mk \
-  tests/plugins/local.mk
+  src/libexpr/tests/local.mk
+endif
+
+ifeq ($(ENABLE_TESTS), yes)
+makefiles += \
+  tests/functional/local.mk \
+  tests/functional/ca/local.mk \
+  tests/functional/dyn-drv/local.mk \
+  tests/functional/test-libstoreconsumer/local.mk \
+  tests/functional/plugins/local.mk
 else
 makefiles += \
   mk/disable-tests.mk

Makefile.config.in

@@ -28,6 +28,8 @@ SODIUM_LIBS = @SODIUM_LIBS@
 SQLITE3_LIBS = @SQLITE3_LIBS@
 bash = @bash@
 bindir = @bindir@
+checkbindir = @checkbindir@
+checklibdir = @checklibdir@
 datadir = @datadir@
 datarootdir = @datarootdir@
 doc_generate = @doc_generate@
@@ -46,5 +48,7 @@ sandbox_shell = @sandbox_shell@
 storedir = @storedir@
 sysconfdir = @sysconfdir@
 system = @system@
-tests = @tests@
+ENABLE_BUILD = @ENABLE_BUILD@
+ENABLE_TESTS = @ENABLE_TESTS@
+INSTALL_UNIT_TESTS = @INSTALL_UNIT_TESTS@
 internal_api_docs = @internal_api_docs@

README.md

@@ -7,21 +7,20 @@ Nix is a powerful package manager for Linux and other Unix systems that makes pa
 management reliable and reproducible. Please refer to the [Nix manual](https://nixos.org/nix/manual)
 for more details.
 
-## Installation
+## Installation and first steps
 
-On Linux and macOS the easiest way to install Nix is to run the following shell command
-(as a user other than root):
+Visit [nix.dev](https://nix.dev) for [installation instructions](https://nix.dev/tutorials/install-nix) and [beginner tutorials](https://nix.dev/tutorials/first-steps).
 
-```console
-$ curl -L https://nixos.org/nix/install | sh
-```
-
-Information on additional installation methods is available on the [Nix download page](https://nixos.org/download.html).
+Full reference documentation can be found in the [Nix manual](https://nixos.org/nix/manual).
 
 ## Building And Developing
 
 See our [Hacking guide](https://nixos.org/manual/nix/unstable/contributing/hacking.html) in our manual for instruction on how to
-to set up a development environment and build Nix from source.
+ set up a development environment and build Nix from source.
+
+## Contributing
+
+Check the [contributing guide](./CONTRIBUTING.md) if you want to get involved with developing Nix.
 
 ## Additional Resources
 
@@ -29,7 +28,6 @@ to set up a development environment and build Nix from source.
 - [Nix jobsets on hydra.nixos.org](https://hydra.nixos.org/project/nix)
 - [NixOS Discourse](https://discourse.nixos.org/)
 - [Matrix - #nix:nixos.org](https://matrix.to/#/#nix:nixos.org)
-- [IRC - #nixos on libera.chat](irc://irc.libera.chat/#nixos)
 
 ## License
 

boehmgc-coroutine-sp-fallback.diff

@@ -59,12 +59,18 @@ index b5d71e62..aed7b0bf 100644
      GC_bool found_me = FALSE;
      size_t nthreads = 0;
      int i;
-@@ -851,6 +853,31 @@ GC_INNER void GC_push_all_stacks(void)
+@@ -851,6 +853,37 @@ GC_INNER void GC_push_all_stacks(void)
            hi = p->altstack + p->altstack_size;
            /* FIXME: Need to scan the normal stack too, but how ? */
            /* FIXME: Assume stack grows down */
 +        } else {
-+          if (pthread_getattr_np(p->id, &pattr)) {
++#ifdef HAVE_PTHREAD_ATTR_GET_NP
++          if (!pthread_attr_init(&pattr)
++              || !pthread_attr_get_np(p->id, &pattr))
++#else /* HAVE_PTHREAD_GETATTR_NP */
++          if (pthread_getattr_np(p->id, &pattr))
++#endif
++          {
 +            ABORT("GC_push_all_stacks: pthread_getattr_np failed!");
 +          }
 +          if (pthread_attr_getstacksize(&pattr, &stack_limit)) {

bootstrap.sh

@@ -1,4 +0,0 @@
-#! /bin/sh -e
-rm -f aclocal.m4
-mkdir -p config
-exec autoreconf -vfi

configure.ac

@@ -5,7 +5,14 @@ AC_CONFIG_AUX_DIR(config)
 
 AC_PROG_SED
 
-# Construct a Nix system name (like "i686-linux").
+# Construct a Nix system name (like "i686-linux"):
+# https://www.gnu.org/software/autoconf/manual/html_node/Canonicalizing.html#index-AC_005fCANONICAL_005fHOST-1
+# The inital value is produced by the `config/config.guess` script:
+# upstream: https://git.savannah.gnu.org/cgit/config.git/tree/config.guess
+# It has the following form, which is not documented anywhere:
+# <cpu>-<vendor>-<os>[<version>][-<abi>]
+# If `./configure` is passed any of the `--host`, `--build`, `--target` options, the value comes from `config/config.sub` instead:
+# upstream: https://git.savannah.gnu.org/cgit/config.git/tree/config.sub
 AC_CANONICAL_HOST
 AC_MSG_CHECKING([for the canonical Nix system name])
 
@@ -61,6 +68,9 @@ case "$host_os" in
 esac
 
 
+ENSURE_NO_GCC_BUG_80431
+
+
 # Check for pubsetbuf.
 AC_MSG_CHECKING([for pubsetbuf])
 AC_LANG_PUSH(C++)
@@ -145,12 +155,29 @@ if test "x$GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC" = xyes; then
     LDFLAGS="-latomic $LDFLAGS"
 fi
 
+# Running the functional tests without building Nix is useful for testing
+# different pre-built versions of Nix against each other.
+AC_ARG_ENABLE(build, AS_HELP_STRING([--disable-build],[Do not build nix]),
+  ENABLE_BUILD=$enableval, ENABLE_BUILD=yes)
+AC_SUBST(ENABLE_BUILD)
 # Building without tests is useful for bootstrapping with a smaller footprint
 # or running the tests in a separate derivation. Otherwise, we do compile and
 # run them.
 AC_ARG_ENABLE(tests, AS_HELP_STRING([--disable-tests],[Do not build the tests]),
-  tests=$enableval, tests=yes)
-AC_SUBST(tests)
+  ENABLE_TESTS=$enableval, ENABLE_TESTS=yes)
+AC_SUBST(ENABLE_TESTS)
+
+AC_ARG_ENABLE(install-unit-tests, AS_HELP_STRING([--enable-install-unit-tests],[Install the unit tests for running later (default no)]),
+  INSTALL_UNIT_TESTS=$enableval, INSTALL_UNIT_TESTS=no)
+AC_SUBST(INSTALL_UNIT_TESTS)
+
+AC_ARG_WITH(check-bin-dir, AS_HELP_STRING([--with-check-bin-dir=PATH],[path to install unit tests for running later (defaults to $libexecdir/nix)]),
+  checkbindir=$withval, checkbindir=$libexecdir/nix)
+AC_SUBST(checkbindir)
+
+AC_ARG_WITH(check-lib-dir, AS_HELP_STRING([--with-check-lib-dir=PATH],[path to install unit tests for running later (defaults to $libdir)]),
+  checklibdir=$withval, checklibdir=$libdir)
+AC_SUBST(checklibdir)
 
 # Building without API docs is the default as Nix' C++ interfaces are internal and unstable.
 AC_ARG_ENABLE(internal_api_docs, AS_HELP_STRING([--enable-internal-api-docs],[Build API docs for Nix's internal unstable C++ interfaces]),
@@ -282,7 +309,7 @@ if test "$gc" = yes; then
 fi
 
 
-if test "$tests" = yes; then
+if test "$ENABLE_TESTS" = yes; then
 
 # Look for gtest.
 PKG_CHECK_MODULES([GTEST], [gtest_main])

doc/internal-api/doxygen.cfg.in

@@ -54,6 +54,23 @@ INPUT                  = \
   src/nix-env \
   src/nix-store
 
+# If the MACRO_EXPANSION tag is set to YES, doxygen will expand all macro names
+# in the source code. If set to NO, only conditional compilation will be
+# performed. Macro expansion can be done in a controlled way by setting
+# EXPAND_ONLY_PREDEF to YES.
+# The default value is: NO.
+# This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
+
+MACRO_EXPANSION        = YES
+
+# If the EXPAND_ONLY_PREDEF and MACRO_EXPANSION tags are both set to YES then
+# the macro expansion is limited to the macros specified with the PREDEFINED and
+# EXPAND_AS_DEFINED tags.
+# The default value is: NO.
+# This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
+
+EXPAND_ONLY_PREDEF     = YES
+
 # The INCLUDE_PATH tag can be used to specify one or more directories that
 # contain include files that are not input files but should be processed by the
 # preprocessor. Note that the INCLUDE_PATH is not recursive, so the setting of
@@ -61,3 +78,16 @@ INPUT                  = \
 # This tag requires that the tag SEARCH_INCLUDES is set to YES.
 
 INCLUDE_PATH           = @RAPIDCHECK_HEADERS@
+
+# If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then this
+# tag can be used to specify a list of macro names that should be expanded. The
+# macro definition that is found in the sources will be used. Use the PREDEFINED
+# tag if you want to use a different macro definition that overrules the
+# definition found in the source code.
+# This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
+
+EXPAND_AS_DEFINED      = \
+  DECLARE_COMMON_SERIALISER \
+  DECLARE_WORKER_SERIALISER \
+  DECLARE_SERVE_SERIALISER \
+  LENGTH_PREFIXED_PROTO_HELPER

doc/manual/generate-builtin-constants.nix

@@ -0,0 +1,31 @@
+let
+  inherit (builtins) concatStringsSep attrValues mapAttrs;
+  inherit (import ./utils.nix) optionalString squash;
+in
+
+builtinsInfo:
+let
+  showBuiltin = name: { doc, type, impure-only }:
+    let
+      type' = optionalString (type != null) " (${type})";
+
+      impureNotice = optionalString impure-only ''
+        > **Note**
+        >
+        > Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).
+      '';
+    in
+    squash ''
+      <dt id="builtins-${name}">
+        <a href="#builtins-${name}"><code>${name}</code></a>${type'}
+      </dt>
+      <dd>
+
+      ${doc}
+
+      ${impureNotice}
+
+      </dd>
+    '';
+in
+concatStringsSep "\n" (attrValues (mapAttrs showBuiltin builtinsInfo))

doc/manual/generate-builtins.nix

@@ -1,24 +1,28 @@
 let
-  inherit (builtins) concatStringsSep attrNames;
+  inherit (builtins) concatStringsSep attrValues mapAttrs;
+  inherit (import ./utils.nix) optionalString squash;
 in
 
 builtinsInfo:
 let
-  showBuiltin = name:
+  showBuiltin = name: { doc, args, arity, experimental-feature }:
     let
-      inherit (builtinsInfo.${name}) doc args;
+      experimentalNotice = optionalString (experimental-feature != null) ''
+        This function is only available if the [${experimental-feature}](@docroot@/contributing/experimental-features.md#xp-feature-${experimental-feature}) experimental feature is enabled.
+      '';
     in
-    ''
+    squash ''
       <dt id="builtins-${name}">
         <a href="#builtins-${name}"><code>${name} ${listArgs args}</code></a>
       </dt>
       <dd>
 
-        ${doc}
+      ${doc}
+
+      ${experimentalNotice}
 
       </dd>
     '';
   listArgs = args: concatStringsSep " " (map (s: "<var>${s}</var>") args);
 in
-concatStringsSep "\n" (map showBuiltin (attrNames builtinsInfo))
-
+concatStringsSep "\n" (attrValues (mapAttrs showBuiltin builtinsInfo))

doc/manual/generate-manpage.nix

@@ -1,11 +1,12 @@
 let
   inherit (builtins)
-    attrNames attrValues fromJSON listToAttrs mapAttrs
+    attrNames attrValues fromJSON listToAttrs mapAttrs groupBy
     concatStringsSep concatMap length lessThan replaceStrings sort;
-  inherit (import ./utils.nix) concatStrings optionalString filterAttrs trim squash unique showSettings;
+  inherit (import <nix/utils.nix>) attrsToList concatStrings optionalString filterAttrs trim squash unique;
+  showStoreDocs = import ./generate-store-info.nix;
 in
 
-commandDump:
+inlineHTML: commandDump:
 
 let
 
@@ -30,7 +31,7 @@ let
 
         ${maybeSubcommands}
 
-        ${maybeDocumentation}
+        ${maybeStoreDocs}
 
         ${maybeOptions}
       '';
@@ -40,15 +41,15 @@ let
           showArgument = arg: "*${arg.label}*" + optionalString (! arg ? arity) "...";
           arguments = concatStringsSep " " (map showArgument args);
         in ''
-         `${command}` [*option*...] ${arguments}
+          `${command}` [*option*...] ${arguments}
         '';
 
       maybeSubcommands = optionalString (details ? commands && details.commands != {})
-         ''
-           where *subcommand* is one of the following:
+        ''
+          where *subcommand* is one of the following:
 
-           ${subcommands}
-         '';
+          ${subcommands}
+        '';
 
       subcommands = if length categories > 1
         then listCategories
@@ -70,40 +71,57 @@ let
         * [`${command} ${name}`](./${appendName filename name}.md) - ${subcmd.description}
       '';
 
-      maybeDocumentation = optionalString
-        (details ? doc)
-        (replaceStrings ["@stores@"] [storeDocs] details.doc);
+      # FIXME: this is a hack.
+      # store parameters should not be part of command documentation to begin
+      # with, but instead be rendered on separate pages.
+      maybeStoreDocs = optionalString (details ? doc)
+        (replaceStrings [ "@stores@" ] [ (showStoreDocs inlineHTML commandInfo.stores) ] details.doc);
 
-      maybeOptions = optionalString (details.flags != {}) ''
+      maybeOptions = let
+        allVisibleOptions = filterAttrs
+          (_: o: ! o.hiddenCategory)
+          (details.flags // toplevel.flags);
+      in optionalString (allVisibleOptions != {}) ''
         # Options
 
-        ${showOptions details.flags toplevel.flags}
+        ${showOptions inlineHTML allVisibleOptions}
+
+        > **Note**
+        >
+        > See [`man nix.conf`](@docroot@/command-ref/conf-file.md#command-line-flags) for overriding configuration settings with command line flags.
       '';
 
-      showOptions = options: commonOptions:
+      showOptions = inlineHTML: allOptions:
         let
-          allOptions = options // commonOptions;
-          showCategory = cat: ''
-            ${optionalString (cat != "") "**${cat}:**"}
+          showCategory = cat: opts: ''
+            ${optionalString (cat != "") "## ${cat}"}
 
-            ${listOptions (filterAttrs (n: v: v.category == cat) allOptions)}
+            ${concatStringsSep "\n" (attrValues (mapAttrs showOption opts))}
             '';
-          listOptions = opts: concatStringsSep "\n" (attrValues (mapAttrs showOption opts));
           showOption = name: option:
             let
+              result = trim ''
+                - ${item}
+
+                  ${option.description}
+              '';
+              item = if inlineHTML
+                then ''<span id="opt-${name}">[`--${name}`](#opt-${name})</span> ${shortName} ${labels}''
+                else "`--${name}` ${shortName} ${labels}";
               shortName = optionalString
                 (option ? shortName)
                 ("/ `-${option.shortName}`");
               labels = optionalString
                 (option ? labels)
                 (concatStringsSep " " (map (s: "*${s}*") option.labels));
-            in trim ''
-              - `--${name}` ${shortName} ${labels}
-
-                ${option.description}
-            '';
-          categories = sort lessThan (unique (map (cmd: cmd.category) (attrValues allOptions)));
-        in concatStrings (map showCategory categories);
+            in result;
+          categories = mapAttrs
+            # Convert each group from a list of key-value pairs back to an attrset
+            (_: listToAttrs)
+            (groupBy
+              (cmd: cmd.value.category)
+              (attrsToList allOptions));
+        in concatStrings (attrValues (mapAttrs showCategory categories));
     in squash result;
 
   appendName = filename: name: (if filename == "nix" then "nix3" else filename) + "-" + name;
@@ -135,18 +153,4 @@ let
       "    - [${page.command}](command-ref/new-cli/${page.name})";
     in concatStringsSep "\n" (map showEntry manpages) + "\n";
 
-  storeDocs =
-    let
-      showStore = name: { settings, doc }:
-        ''
-          ## ${name}
-
-          ${doc}
-
-          **Settings**:
-
-          ${showSettings { useAnchors = false; } settings}
-        '';
-    in concatStrings (attrValues (mapAttrs showStore commandInfo.stores));
-
 in (listToAttrs manpages) // { "SUMMARY.md" = tableOfContents; }

doc/manual/generate-settings.nix

@@ -0,0 +1,66 @@
+let
+  inherit (builtins) attrValues concatStringsSep isAttrs isBool mapAttrs;
+  inherit (import ./utils.nix) concatStrings indent optionalString squash;
+in
+
+# `inlineHTML` is a hack to accommodate inconsistent output from `lowdown`
+{ prefix, inlineHTML ? true }: settingsInfo:
+
+let
+
+  showSetting = prefix: setting: { description, documentDefault, defaultValue, aliases, value, experimentalFeature }:
+    let
+      result = squash ''
+          - ${item}
+
+          ${indent "  " body}
+        '';
+      item = if inlineHTML
+        then ''<span id="${prefix}-${setting}">[`${setting}`](#${prefix}-${setting})</span>''
+        else "`${setting}`";
+      # separate body to cleanly handle indentation
+      body = ''
+          ${description}
+
+          ${experimentalFeatureNote}
+
+          **Default:** ${showDefault documentDefault defaultValue}
+
+          ${showAliases aliases}
+        '';
+
+      experimentalFeatureNote = optionalString (experimentalFeature != null) ''
+          > **Warning**
+          > This setting is part of an
+          > [experimental feature](@docroot@/contributing/experimental-features.md).
+
+          To change this setting, you need to make sure the corresponding experimental feature,
+          [`${experimentalFeature}`](@docroot@/contributing/experimental-features.md#xp-feature-${experimentalFeature}),
+          is enabled.
+          For example, include the following in [`nix.conf`](#):
+
+          ```
+          extra-experimental-features = ${experimentalFeature}
+          ${setting} = ...
+          ```
+        '';
+
+      showDefault = documentDefault: defaultValue:
+        if documentDefault then
+          # a StringMap value type is specified as a string, but
+          # this shows the value type. The empty stringmap is `null` in
+          # JSON, but that converts to `{ }` here.
+          if defaultValue == "" || defaultValue == [] || isAttrs defaultValue
+            then "*empty*"
+            else if isBool defaultValue then
+              if defaultValue then "`true`" else "`false`"
+            else "`${toString defaultValue}`"
+        else "*machine-specific*";
+
+      showAliases = aliases:
+          optionalString (aliases != [])
+            "**Deprecated alias:** ${(concatStringsSep ", " (map (s: "`${s}`") aliases))}";
+
+    in result;
+
+in concatStrings (attrValues (mapAttrs (showSetting prefix) settingsInfo))

doc/manual/generate-store-info.nix

@@ -0,0 +1,45 @@
+let
+  inherit (builtins) attrValues mapAttrs;
+  inherit (import ./utils.nix) concatStrings optionalString;
+  showSettings = import ./generate-settings.nix;
+in
+
+inlineHTML: storesInfo:
+
+let
+
+  showStore = name: { settings, doc, experimentalFeature }:
+    let
+
+    result = ''
+      ## ${name}
+
+      ${doc}
+
+      ${experimentalFeatureNote}
+
+      ### Settings
+
+      ${showSettings { prefix = "store-${slug}"; inherit inlineHTML; } settings}
+    '';
+
+      # markdown doesn't like spaces in URLs
+      slug = builtins.replaceStrings [ " " ] [ "-" ] name;
+
+    experimentalFeatureNote = optionalString (experimentalFeature != null) ''
+      > **Warning**
+      > This store is part of an
+      > [experimental feature](@docroot@/contributing/experimental-features.md).
+
+      To use this store, you need to make sure the corresponding experimental feature,
+      [`${experimentalFeature}`](@docroot@/contributing/experimental-features.md#xp-feature-${experimentalFeature}),
+      is enabled.
+      For example, include the following in [`nix.conf`](#):
+
+      ```
+      extra-experimental-features = ${experimentalFeature}
+      ```
+    '';
+  in result;
+
+in concatStrings (attrValues (mapAttrs showStore storesInfo))

doc/manual/local.mk

@@ -32,7 +32,7 @@ dummy-env = env -i \
 	NIX_STATE_DIR=/dummy \
 	NIX_CONFIG='cores = 0'
 
-nix-eval = $(dummy-env) $(bindir)/nix eval --experimental-features nix-command -I nix/corepkgs=corepkgs --store dummy:// --impure --raw
+nix-eval = $(dummy-env) $(bindir)/nix eval --experimental-features nix-command -I nix=doc/manual --store dummy:// --impure --raw
 
 # re-implement mdBook's include directive to make it usable for terminal output and for proper @docroot@ substitution
 define process-includes
@@ -96,14 +96,14 @@ $(d)/src/SUMMARY.md: $(d)/src/SUMMARY.md.in $(d)/src/command-ref/new-cli $(d)/sr
 	@cp $< $@
 	@$(call process-includes,$@,$@)
 
-$(d)/src/command-ref/new-cli: $(d)/nix.json $(d)/utils.nix $(d)/generate-manpage.nix $(bindir)/nix
+$(d)/src/command-ref/new-cli: $(d)/nix.json $(d)/utils.nix $(d)/generate-manpage.nix $(d)/generate-settings.nix $(d)/generate-store-info.nix $(bindir)/nix
 	@rm -rf $@ $@.tmp
-	$(trace-gen) $(nix-eval) --write-to $@.tmp --expr 'import doc/manual/generate-manpage.nix (builtins.readFile $<)'
+	$(trace-gen) $(nix-eval) --write-to $@.tmp --expr 'import doc/manual/generate-manpage.nix true (builtins.readFile $<)'
 	@mv $@.tmp $@
 
-$(d)/src/command-ref/conf-file.md: $(d)/conf-file.json $(d)/utils.nix $(d)/src/command-ref/conf-file-prefix.md $(d)/src/command-ref/experimental-features-shortlist.md $(bindir)/nix
+$(d)/src/command-ref/conf-file.md: $(d)/conf-file.json $(d)/utils.nix $(d)/generate-settings.nix $(d)/src/command-ref/conf-file-prefix.md $(d)/src/command-ref/experimental-features-shortlist.md $(bindir)/nix
 	@cat doc/manual/src/command-ref/conf-file-prefix.md > $@.tmp
-	$(trace-gen) $(nix-eval) --expr '(import doc/manual/utils.nix).showSettings { useAnchors = true; } (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp;
+	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-settings.nix { prefix = "conf"; } (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp;
 	@mv $@.tmp $@
 
 $(d)/nix.json: $(bindir)/nix
@@ -125,17 +125,23 @@ $(d)/src/command-ref/experimental-features-shortlist.md: $(d)/xp-features.json $
 	@mv $@.tmp $@
 
 $(d)/xp-features.json: $(bindir)/nix
-	$(trace-gen) $(dummy-env) NIX_PATH=nix/corepkgs=corepkgs $(bindir)/nix __dump-xp-features > $@.tmp
+	$(trace-gen) $(dummy-env) $(bindir)/nix __dump-xp-features > $@.tmp
 	@mv $@.tmp $@
 
-$(d)/src/language/builtins.md: $(d)/builtins.json $(d)/generate-builtins.nix $(d)/src/language/builtins-prefix.md $(bindir)/nix
+$(d)/src/language/builtins.md: $(d)/language.json $(d)/generate-builtins.nix $(d)/src/language/builtins-prefix.md $(bindir)/nix
 	@cat doc/manual/src/language/builtins-prefix.md > $@.tmp
-	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtins.nix (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp;
+	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtins.nix (builtins.fromJSON (builtins.readFile $<)).builtins' >> $@.tmp;
 	@cat doc/manual/src/language/builtins-suffix.md >> $@.tmp
 	@mv $@.tmp $@
 
-$(d)/builtins.json: $(bindir)/nix
-	$(trace-gen) $(dummy-env) NIX_PATH=nix/corepkgs=corepkgs $(bindir)/nix __dump-builtins > $@.tmp
+$(d)/src/language/builtin-constants.md: $(d)/language.json $(d)/generate-builtin-constants.nix $(d)/src/language/builtin-constants-prefix.md $(bindir)/nix
+	@cat doc/manual/src/language/builtin-constants-prefix.md > $@.tmp
+	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtin-constants.nix (builtins.fromJSON (builtins.readFile $<)).constants' >> $@.tmp;
+	@cat doc/manual/src/language/builtin-constants-suffix.md >> $@.tmp
+	@mv $@.tmp $@
+
+$(d)/language.json: $(bindir)/nix
+	$(trace-gen) $(dummy-env) $(bindir)/nix __dump-language > $@.tmp
 	@mv $@.tmp $@
 
 # Generate the HTML manual.
@@ -167,14 +173,18 @@ doc/manual/generated/man1/nix3-manpages: $(d)/src/command-ref/new-cli
 	done
 	@touch $@
 
-$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.jq $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/command-ref/new-cli $(d)/src/contributing/experimental-feature-descriptions.md $(d)/src/command-ref/conf-file.md $(d)/src/language/builtins.md
+# the `! -name 'contributing.md'` filter excludes the one place where
+# `@docroot@` is to be preserved for documenting the mechanism
+# FIXME: maybe contributing guides should live right next to the code
+# instead of in the manual
+$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.jq $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/command-ref/new-cli $(d)/src/contributing/experimental-feature-descriptions.md $(d)/src/command-ref/conf-file.md $(d)/src/language/builtins.md $(d)/src/language/builtin-constants.md
 	$(trace-gen) \
 		tmp="$$(mktemp -d)"; \
 		cp -r doc/manual "$$tmp"; \
 		find "$$tmp" -name '*.md' | while read -r file; do \
 			$(call process-includes,$$file,$$file); \
 		done; \
-		find "$$tmp" -name '*.md' | while read -r file; do \
+		find "$$tmp" -name '*.md' ! -name 'documentation.md' | while read -r file; do \
 			docroot="$$(realpath --relative-to="$$(dirname "$$file")" $$tmp/manual/src)"; \
 			sed -i "s,@docroot@,$$docroot,g" "$$file"; \
 		done; \

doc/manual/redirects.js

@@ -281,7 +281,7 @@ const redirects = {
     "chap-introduction": "introduction.html",
     "ch-basic-package-mgmt": "package-management/basic-package-mgmt.html",
     "ssec-binary-cache-substituter": "package-management/binary-cache-substituter.html",
-    "sec-channels": "package-management/channels.html",
+    "sec-channels": "command-ref/nix-channel.html",
     "ssec-copy-closure": "package-management/copy-closure.html",
     "sec-garbage-collection": "package-management/garbage-collection.html",
     "ssec-gc-roots": "package-management/garbage-collector-roots.html",
@@ -330,17 +330,31 @@ const redirects = {
     "ssec-relnotes-2.0": "release-notes/rl-2.0.html",
     "ssec-relnotes-2.1": "release-notes/rl-2.1.html",
     "ssec-relnotes-2.2": "release-notes/rl-2.2.html",
-    "ssec-relnotes-2.3": "release-notes/rl-2.3.html"
+    "ssec-relnotes-2.3": "release-notes/rl-2.3.html",
   },
   "language/values.html": {
     "simple-values": "#primitives",
     "lists": "#list",
     "strings": "#string",
-    "lists": "#list",
-    "attribute-sets": "#attribute-set"
+    "attribute-sets": "#attribute-set",
   },
   "installation/installing-binary.html": {
-    "uninstalling": "uninstall.html"
+    "linux": "uninstall.html#linux",
+    "macos": "uninstall.html#macos",
+    "uninstalling": "uninstall.html",
+  },
+  "contributing/hacking.html": {
+    "nix-with-flakes": "#building-nix-with-flakes",
+    "classic-nix": "#building-nix",
+    "running-tests": "testing.html#running-tests",
+    "unit-tests": "testing.html#unit-tests",
+    "functional-tests": "testing.html#functional-tests",
+    "debugging-failing-functional-tests": "testing.html#debugging-failing-functional-tests",
+    "integration-tests": "testing.html#integration-tests",
+    "installer-tests": "testing.html#installer-tests",
+    "one-time-setup": "testing.html#one-time-setup",
+    "using-the-ci-generated-installer-for-manual-testing": "testing.html#using-the-ci-generated-installer-for-manual-testing",
+    "characterization-testing": "#characterisation-testing-unit",
   }
 };
 

doc/manual/src/SUMMARY.md.in

@@ -16,27 +16,31 @@
   - [Environment Variables](installation/env-variables.md)
   - [Upgrading Nix](installation/upgrading.md)
   - [Uninstalling Nix](installation/uninstall.md)
+- [Nix Store](store/index.md)
+  - [File System Object](store/file-system-object.md)
+  - [Store Object](store/store-object.md)
+  - [Store Path](store/store-path.md)
+- [Nix Language](language/index.md)
+  - [Data Types](language/values.md)
+  - [Language Constructs](language/constructs.md)
+    - [String interpolation](language/string-interpolation.md)
+    - [Lookup path](language/constructs/lookup-path.md)
+  - [Operators](language/operators.md)
+  - [Derivations](language/derivations.md)
+    - [Advanced Attributes](language/advanced-attributes.md)
+    - [Import From Derivation](language/import-from-derivation.md)
+  - [Built-in Constants](language/builtin-constants.md)
+  - [Built-in Functions](language/builtins.md)
 - [Package Management](package-management/package-management.md)
-  - [Basic Package Management](package-management/basic-package-mgmt.md)
   - [Profiles](package-management/profiles.md)
   - [Garbage Collection](package-management/garbage-collection.md)
     - [Garbage Collector Roots](package-management/garbage-collector-roots.md)
-  - [Channels](package-management/channels.md)
+- [Advanced Topics](advanced-topics/advanced-topics.md)
   - [Sharing Packages Between Machines](package-management/sharing-packages.md)
     - [Serving a Nix store via HTTP](package-management/binary-cache-substituter.md)
     - [Copying Closures via SSH](package-management/copy-closure.md)
     - [Serving a Nix store via SSH](package-management/ssh-substituter.md)
     - [Serving a Nix store via S3](package-management/s3-substituter.md)
-- [Nix Language](language/index.md)
-  - [Data Types](language/values.md)
-  - [Language Constructs](language/constructs.md)
-    - [String interpolation](language/string-interpolation.md)
-  - [Operators](language/operators.md)
-  - [Derivations](language/derivations.md)
-    - [Advanced Attributes](language/advanced-attributes.md)
-  - [Built-in Constants](language/builtin-constants.md)
-  - [Built-in Functions](language/builtins.md)
-- [Advanced Topics](advanced-topics/advanced-topics.md)
   - [Remote Builds](advanced-topics/distributed-builds.md)
   - [Tuning Cores and Jobs](advanced-topics/cores-vs-jobs.md)
   - [Verifying Build Reproducibility](advanced-topics/diff-hook.md)
@@ -97,15 +101,23 @@
       - [manifest.json](command-ref/files/manifest.json.md)
     - [Channels](command-ref/files/channels.md)
     - [Default Nix expression](command-ref/files/default-nix-expression.md)
-- [Architecture](architecture/architecture.md)
+- [Architecture and Design](architecture/architecture.md)
+- [Protocols](protocols/protocols.md)
+  - [Serving Tarball Flakes](protocols/tarball-fetcher.md)
+  - [Derivation "ATerm" file format](protocols/derivation-aterm.md)
 - [Glossary](glossary.md)
 - [Contributing](contributing/contributing.md)
   - [Hacking](contributing/hacking.md)
+  - [Testing](contributing/testing.md)
+  - [Documentation](contributing/documentation.md)
   - [Experimental Features](contributing/experimental-features.md)
   - [CLI guideline](contributing/cli-guideline.md)
+  - [C++ style guide](contributing/cxx.md)
 - [Release Notes](release-notes/release-notes.md)
-  - [Release X.Y (202?-??-??)](release-notes/rl-next.md)
-  - [Release 2.16 (2023-05-21)](release-notes/rl-2.16.md)
+  - [Release 2.19 (2023-11-17)](release-notes/rl-2.19.md)
+  - [Release 2.18 (2023-09-20)](release-notes/rl-2.18.md)
+  - [Release 2.17 (2023-07-24)](release-notes/rl-2.17.md)
+  - [Release 2.16 (2023-05-31)](release-notes/rl-2.16.md)
   - [Release 2.15 (2023-04-11)](release-notes/rl-2.15.md)
   - [Release 2.14 (2023-02-28)](release-notes/rl-2.14.md)
   - [Release 2.13 (2023-01-17)](release-notes/rl-2.13.md)

doc/manual/src/advanced-topics/advanced-topics.md

@@ -1 +1 @@
-
+This section lists advanced topics related to builds and builds performance

doc/manual/src/advanced-topics/distributed-builds.md

@@ -12,14 +12,14 @@ machine is accessible via SSH and that it has Nix installed. You can
 test whether connecting to the remote Nix instance works, e.g.
 
 ```console
-$ nix store ping --store ssh://mac
+$ nix store info --store ssh://mac
 ```
 
 will try to connect to the machine named `mac`. It is possible to
 specify an SSH identity file as part of the remote store URI, e.g.
 
 ```console
-$ nix store ping --store ssh://mac?ssh-key=/home/alice/my-key
+$ nix store info --store ssh://mac?ssh-key=/home/alice/my-key
 ```
 
 Since builds should be non-interactive, the key should not have a

doc/manual/src/advanced-topics/post-build-hook.md

@@ -17,9 +17,8 @@ the build loop.
 
 # Prerequisites
 
-This tutorial assumes you have [configured an S3-compatible binary
-cache](../package-management/s3-substituter.md), and that the `root`
-user's default AWS profile can upload to the bucket.
+This tutorial assumes you have configured an [S3-compatible binary cache](@docroot@/command-ref/new-cli/nix3-help-stores.md#s3-binary-cache-store) as a [substituter](../command-ref/conf-file.md#conf-substituters),
+and that the `root` user's default AWS profile can upload to the bucket.
 
 # Set up a Signing Key
 
@@ -69,6 +68,8 @@ exec nix copy --to "s3://example-nix-cache" $OUT_PATHS
 > store sign`. Nix guarantees the paths will not contain any spaces,
 > however a store path might contain glob characters. The `set -f`
 > disables globbing in the shell.
+> If you want to upload the `.drv` file too, the `$DRV_PATH` variable
+> is also defined for the script and works just like `$OUT_PATHS`.
 
 Then make sure the hook program is executable by the `root` user:
 

doc/manual/src/architecture/architecture.md

@@ -7,11 +7,11 @@ It should help users understand why Nix behaves as it does, and it should help d
 
 Nix consists of [hierarchical layers].
 
-[hierarchical layers]: https://en.m.wikipedia.org/wiki/Multitier_architecture#Layers
+[hierarchical layers]: https://en.wikipedia.org/wiki/Multitier_architecture#Layers
 
 The following [concept map] shows its main components (rectangles), the objects they operate on (rounded rectangles), and their interactions (connecting phrases):
 
-[concept map]: https://en.m.wikipedia.org/wiki/Concept_map
+[concept map]: https://en.wikipedia.org/wiki/Concept_map
 
 ```
 
@@ -59,10 +59,11 @@ The [Nix language](../language/index.md) evaluator transforms Nix expressions in
 The command line interface and Nix expressions are what users deal with most.
 
 > **Note**
+>
 > The Nix language itself does not have a notion of *packages* or *configurations*.
 > As far as we are concerned here, the inputs and results of a build plan are just data.
 
-Underlying the command line interface and the Nix language evaluator is the [Nix store](../glossary.md#gloss-store), a mechanism to keep track of build plans, data, and references between them.
+Underlying the command line interface and the Nix language evaluator is the [Nix store](../store/index.md), a mechanism to keep track of build plans, data, and references between them.
 It can also execute build plans to produce new data, which are made available to the operating system as files.
 
 A build plan itself is a series of *build tasks*, together with their build inputs.
@@ -76,7 +77,7 @@ The result of a build task can be input to another build task.
 The following [data flow diagram] shows a build plan for illustration.
 Build inputs used as instructions to a build task are marked accordingly:
 
-[data flow diagram]: https://en.m.wikipedia.org/wiki/Data-flow_diagram
+[data flow diagram]: https://en.wikipedia.org/wiki/Data-flow_diagram
 
 ```
 +--------------------------------------------------------------------+

doc/manual/src/command-ref/conf-file-prefix.md

@@ -4,49 +4,67 @@
 
 # Description
 
-By default Nix reads settings from the following places:
+Nix supports a variety of configuration settings, which are read from configuration files or taken as command line flags.
 
-  - The system-wide configuration file `sysconfdir/nix/nix.conf` (i.e.
-    `/etc/nix/nix.conf` on most systems), or `$NIX_CONF_DIR/nix.conf` if
-    `NIX_CONF_DIR` is set. Values loaded in this file are not forwarded
-    to the Nix daemon. The client assumes that the daemon has already
-    loaded them.
+## Configuration file
 
-  - If `NIX_USER_CONF_FILES` is set, then each path separated by `:`
-    will be loaded in reverse order.
+By default Nix reads settings from the following places, in that order:
 
-    Otherwise it will look for `nix/nix.conf` files in `XDG_CONFIG_DIRS`
-    and `XDG_CONFIG_HOME`. If unset, `XDG_CONFIG_DIRS` defaults to
-    `/etc/xdg`, and `XDG_CONFIG_HOME` defaults to `$HOME/.config`
-    as per [XDG Base Directory Specification](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html).
+1. The system-wide configuration file `sysconfdir/nix/nix.conf` (i.e. `/etc/nix/nix.conf` on most systems), or `$NIX_CONF_DIR/nix.conf` if [`NIX_CONF_DIR`](./env-common.md#env-NIX_CONF_DIR) is set.
 
-  - If `NIX_CONFIG` is set, its contents is treated as the contents of
-    a configuration file.
+   Values loaded in this file are not forwarded to the Nix daemon.
+   The client assumes that the daemon has already loaded them.
 
-The configuration files consist of `name = value` pairs, one per
-line. Other files can be included with a line like `include path`,
-where *path* is interpreted relative to the current conf file and a
-missing file is an error unless `!include` is used instead. Comments
-start with a `#` character. Here is an example configuration file:
+1. If [`NIX_USER_CONF_FILES`](./env-common.md#env-NIX_USER_CONF_FILES) is set, then each path separated by `:` will be loaded in reverse order.
 
-    keep-outputs = true       # Nice for developers
-    keep-derivations = true   # Idem
+   Otherwise it will look for `nix/nix.conf` files in `XDG_CONFIG_DIRS` and [`XDG_CONFIG_HOME`](./env-common.md#env-XDG_CONFIG_HOME).
+   If unset, `XDG_CONFIG_DIRS` defaults to `/etc/xdg`, and `XDG_CONFIG_HOME` defaults to `$HOME/.config` as per [XDG Base Directory Specification](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html).
 
-You can override settings on the command line using the `--option`
-flag, e.g. `--option keep-outputs false`. Every configuration setting
-also has a corresponding command line flag, e.g. `--max-jobs 16`; for
-Boolean settings, there are two flags to enable or disable the setting
-(e.g. `--keep-failed` and `--no-keep-failed`).
+1. If [`NIX_CONFIG`](./env-common.md#env-NIX_CONFIG) is set, its contents are treated as the contents of a configuration file.
 
-A configuration setting usually overrides any previous value. However,
-you can prefix the name of the setting by `extra-` to *append* to the
-previous value. For instance,
+### File format
 
-    substituters = a b
-    extra-substituters = c d
+Configuration files consist of `name = value` pairs, one per line.
+Comments start with a `#` character.
 
-defines the `substituters` setting to be `a b c d`. This is also
-available as a command line flag (e.g. `--extra-substituters`).
+Example:
 
-The following settings are currently available:
+```
+keep-outputs = true       # Nice for developers
+keep-derivations = true   # Idem
+```
+
+Other files can be included with a line like `include <path>`, where `<path>` is interpreted relative to the current configuration file.
+A missing file is an error unless `!include` is used instead.
+
+A configuration setting usually overrides any previous value.
+However, for settings that take a list of items, you can prefix the name of the setting by `extra-` to *append* to the previous value.
+
+For instance,
+
+```
+substituters = a b
+extra-substituters = c d
+```
+
+defines the `substituters` setting to be `a b c d`.
+
+Unknown option names are not an error, and are simply ignored with a warning.
+
+## Command line flags
+
+Configuration options can be set on the command line, overriding the values set in the [configuration file](#configuration-file):
+
+- Every configuration setting has corresponding command line flag (e.g. `--max-jobs 16`).
+  Boolean settings do not need an argument, and can be explicitly disabled with the `no-` prefix (e.g. `--keep-failed` and `--no-keep-failed`).
+
+  Unknown option names are invalid flags (unless there is already a flag with that name), and are rejected with an error.
+
+- The flag `--option <name> <value>` is interpreted exactly like a `<name> = <value>` in a setting file.
+
+  Unknown option names are ignored with a warning.
+
+The `extra-` prefix is supported for settings that take a list of items (e.g. `--extra-trusted users alice` or `--option extra-trusted-users alice`).
+
+# Available settings
 

doc/manual/src/command-ref/env-common.md

@@ -2,109 +2,124 @@
 
 Most Nix commands interpret the following environment variables:
 
-  - <span id="env-IN_NIX_SHELL">[`IN_NIX_SHELL`](#env-IN_NIX_SHELL)</span>\
-    Indicator that tells if the current environment was set up by
-    `nix-shell`. It can have the values `pure` or `impure`.
+- <span id="env-IN_NIX_SHELL">[`IN_NIX_SHELL`](#env-IN_NIX_SHELL)</span>
 
-  - <span id="env-NIX_PATH">[`NIX_PATH`](#env-NIX_PATH)</span>\
-    A colon-separated list of directories used to look up the location of Nix
-    expressions using [paths](@docroot@/language/values.md#type-path)
-    enclosed in angle brackets (i.e., `<path>`),
-    e.g. `/home/eelco/Dev:/etc/nixos`. It can be extended using the
-    [`-I` option](@docroot@/command-ref/opt-common.md#opt-I).
+  Indicator that tells if the current environment was set up by
+  `nix-shell`. It can have the values `pure` or `impure`.
 
-    If `NIX_PATH` is not set at all, Nix will fall back to the following list in [impure](@docroot@/command-ref/conf-file.md#conf-pure-eval) and [unrestricted](@docroot@/command-ref/conf-file.md#conf-restrict-eval) evaluation mode:
+- <span id="env-NIX_PATH">[`NIX_PATH`](#env-NIX_PATH)</span>
 
-      1. `$HOME/.nix-defexpr/channels`
-      2. `nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixpkgs`
-      3. `/nix/var/nix/profiles/per-user/root/channels`
+  A colon-separated list of directories used to look up the location of Nix
+  expressions using [paths](@docroot@/language/values.md#type-path)
+  enclosed in angle brackets (i.e., `<path>`),
+  e.g. `/home/eelco/Dev:/etc/nixos`. It can be extended using the
+  [`-I` option](@docroot@/command-ref/opt-common.md#opt-I).
 
-    If `NIX_PATH` is set to an empty string, resolving search paths will always fail.
-    For example, attempting to use `<nixpkgs>` will produce:
+  If `NIX_PATH` is not set at all, Nix will fall back to the following list in [impure](@docroot@/command-ref/conf-file.md#conf-pure-eval) and [unrestricted](@docroot@/command-ref/conf-file.md#conf-restrict-eval) evaluation mode:
 
-        error: file 'nixpkgs' was not found in the Nix search path
+  1. `$HOME/.nix-defexpr/channels`
+  2. `nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixpkgs`
+  3. `/nix/var/nix/profiles/per-user/root/channels`
 
-  - <span id="env-NIX_IGNORE_SYMLINK_STORE">[`NIX_IGNORE_SYMLINK_STORE`](#env-NIX_IGNORE_SYMLINK_STORE)</span>\
-    Normally, the Nix store directory (typically `/nix/store`) is not
-    allowed to contain any symlink components. This is to prevent
-    “impure” builds. Builders sometimes “canonicalise” paths by
-    resolving all symlink components. Thus, builds on different machines
-    (with `/nix/store` resolving to different locations) could yield
-    different results. This is generally not a problem, except when
-    builds are deployed to machines where `/nix/store` resolves
-    differently. If you are sure that you’re not going to do that, you
-    can set `NIX_IGNORE_SYMLINK_STORE` to `1`.
+  If `NIX_PATH` is set to an empty string, resolving search paths will always fail.
+  For example, attempting to use `<nixpkgs>` will produce:
 
-    Note that if you’re symlinking the Nix store so that you can put it
-    on another file system than the root file system, on Linux you’re
-    better off using `bind` mount points, e.g.,
+      error: file 'nixpkgs' was not found in the Nix search path
 
-    ```console
-    $ mkdir /nix
-    $ mount -o bind /mnt/otherdisk/nix /nix
-    ```
+- <span id="env-NIX_IGNORE_SYMLINK_STORE">[`NIX_IGNORE_SYMLINK_STORE`](#env-NIX_IGNORE_SYMLINK_STORE)</span>
 
-    Consult the mount 8 manual page for details.
+  Normally, the Nix store directory (typically `/nix/store`) is not
+  allowed to contain any symlink components. This is to prevent
+  “impure” builds. Builders sometimes “canonicalise” paths by
+  resolving all symlink components. Thus, builds on different machines
+  (with `/nix/store` resolving to different locations) could yield
+  different results. This is generally not a problem, except when
+  builds are deployed to machines where `/nix/store` resolves
+  differently. If you are sure that you’re not going to do that, you
+  can set `NIX_IGNORE_SYMLINK_STORE` to `1`.
 
-  - <span id="env-NIX_STORE_DIR">[`NIX_STORE_DIR`](#env-NIX_STORE_DIR)</span>\
-    Overrides the location of the Nix store (default `prefix/store`).
+  Note that if you’re symlinking the Nix store so that you can put it
+  on another file system than the root file system, on Linux you’re
+  better off using `bind` mount points, e.g.,
 
-  - <span id="env-NIX_DATA_DIR">[`NIX_DATA_DIR`](#env-NIX_DATA_DIR)</span>\
-    Overrides the location of the Nix static data directory (default
-    `prefix/share`).
+  ```console
+  $ mkdir /nix
+  $ mount -o bind /mnt/otherdisk/nix /nix
+  ```
 
-  - <span id="env-NIX_LOG_DIR">[`NIX_LOG_DIR`](#env-NIX_LOG_DIR)</span>\
-    Overrides the location of the Nix log directory (default
-    `prefix/var/log/nix`).
+  Consult the mount 8 manual page for details.
 
-  - <span id="env-NIX_STATE_DIR">[`NIX_STATE_DIR`](#env-NIX_STATE_DIR)</span>\
-    Overrides the location of the Nix state directory (default
-    `prefix/var/nix`).
+- <span id="env-NIX_STORE_DIR">[`NIX_STORE_DIR`](#env-NIX_STORE_DIR)</span>
 
-  - <span id="env-NIX_CONF_DIR">[`NIX_CONF_DIR`](#env-NIX_CONF_DIR)</span>\
-    Overrides the location of the system Nix configuration directory
-    (default `prefix/etc/nix`).
+  Overrides the location of the Nix store (default `prefix/store`).
 
-  - <span id="env-NIX_CONFIG">[`NIX_CONFIG`](#env-NIX_CONFIG)</span>\
-    Applies settings from Nix configuration from the environment.
-    The content is treated as if it was read from a Nix configuration file.
-    Settings are separated by the newline character.
+- <span id="env-NIX_DATA_DIR">[`NIX_DATA_DIR`](#env-NIX_DATA_DIR)</span>
 
-  - <span id="env-NIX_USER_CONF_FILES">[`NIX_USER_CONF_FILES`](#env-NIX_USER_CONF_FILES)</span>\
-    Overrides the location of the Nix user configuration files to load from.
+  Overrides the location of the Nix static data directory (default
+  `prefix/share`).
 
-    The default are the locations according to the [XDG Base Directory Specification].
-    See the [XDG Base Directories](#xdg-base-directories) sub-section for details.
+- <span id="env-NIX_LOG_DIR">[`NIX_LOG_DIR`](#env-NIX_LOG_DIR)</span>
 
-    The variable is treated as a list separated by the `:` token.
+  Overrides the location of the Nix log directory (default
+  `prefix/var/log/nix`).
 
-  - <span id="env-TMPDIR">[`TMPDIR`](#env-TMPDIR)</span>\
-    Use the specified directory to store temporary files. In particular,
-    this includes temporary build directories; these can take up
-    substantial amounts of disk space. The default is `/tmp`.
+- <span id="env-NIX_STATE_DIR">[`NIX_STATE_DIR`](#env-NIX_STATE_DIR)</span>
 
-  - <span id="env-NIX_REMOTE">[`NIX_REMOTE`](#env-NIX_REMOTE)</span>\
-    This variable should be set to `daemon` if you want to use the Nix
-    daemon to execute Nix operations. This is necessary in [multi-user
-    Nix installations](@docroot@/installation/multi-user.md). If the Nix
-    daemon's Unix socket is at some non-standard path, this variable
-    should be set to `unix://path/to/socket`. Otherwise, it should be
-    left unset.
+  Overrides the location of the Nix state directory (default
+  `prefix/var/nix`).
 
-  - <span id="env-NIX_SHOW_STATS">[`NIX_SHOW_STATS`](#env-NIX_SHOW_STATS)</span>\
-    If set to `1`, Nix will print some evaluation statistics, such as
-    the number of values allocated.
+- <span id="env-NIX_CONF_DIR">[`NIX_CONF_DIR`](#env-NIX_CONF_DIR)</span>
 
-  - <span id="env-NIX_COUNT_CALLS">[`NIX_COUNT_CALLS`](#env-NIX_COUNT_CALLS)</span>\
-    If set to `1`, Nix will print how often functions were called during
-    Nix expression evaluation. This is useful for profiling your Nix
-    expressions.
+  Overrides the location of the system Nix configuration directory
+  (default `prefix/etc/nix`).
 
-  - <span id="env-GC_INITIAL_HEAP_SIZE">[`GC_INITIAL_HEAP_SIZE`](#env-GC_INITIAL_HEAP_SIZE)</span>\
-    If Nix has been configured to use the Boehm garbage collector, this
-    variable sets the initial size of the heap in bytes. It defaults to
-    384 MiB. Setting it to a low value reduces memory consumption, but
-    will increase runtime due to the overhead of garbage collection.
+- <span id="env-NIX_CONFIG">[`NIX_CONFIG`](#env-NIX_CONFIG)</span>
+
+  Applies settings from Nix configuration from the environment.
+  The content is treated as if it was read from a Nix configuration file.
+  Settings are separated by the newline character.
+
+- <span id="env-NIX_USER_CONF_FILES">[`NIX_USER_CONF_FILES`](#env-NIX_USER_CONF_FILES)</span>
+
+  Overrides the location of the Nix user configuration files to load from.
+
+  The default are the locations according to the [XDG Base Directory Specification].
+  See the [XDG Base Directories](#xdg-base-directories) sub-section for details.
+
+  The variable is treated as a list separated by the `:` token.
+
+- <span id="env-TMPDIR">[`TMPDIR`](#env-TMPDIR)</span>
+
+  Use the specified directory to store temporary files. In particular,
+  this includes temporary build directories; these can take up
+  substantial amounts of disk space. The default is `/tmp`.
+
+- <span id="env-NIX_REMOTE">[`NIX_REMOTE`](#env-NIX_REMOTE)</span>
+
+  This variable should be set to `daemon` if you want to use the Nix
+  daemon to execute Nix operations. This is necessary in [multi-user
+  Nix installations](@docroot@/installation/multi-user.md). If the Nix
+  daemon's Unix socket is at some non-standard path, this variable
+  should be set to `unix://path/to/socket`. Otherwise, it should be
+  left unset.
+
+- <span id="env-NIX_SHOW_STATS">[`NIX_SHOW_STATS`](#env-NIX_SHOW_STATS)</span>
+
+  If set to `1`, Nix will print some evaluation statistics, such as
+  the number of values allocated.
+
+- <span id="env-NIX_COUNT_CALLS">[`NIX_COUNT_CALLS`](#env-NIX_COUNT_CALLS)</span>
+
+  If set to `1`, Nix will print how often functions were called during
+  Nix expression evaluation. This is useful for profiling your Nix
+  expressions.
+
+- <span id="env-GC_INITIAL_HEAP_SIZE">[`GC_INITIAL_HEAP_SIZE`](#env-GC_INITIAL_HEAP_SIZE)</span>
+
+  If Nix has been configured to use the Boehm garbage collector, this
+  variable sets the initial size of the heap in bytes. It defaults to
+  384 MiB. Setting it to a low value reduces memory consumption, but
+  will increase runtime due to the overhead of garbage collection.
 
 ## XDG Base Directories
 

doc/manual/src/command-ref/nix-build.md

@@ -51,8 +51,9 @@ derivation).
 
 # Options
 
-All options not listed here are passed to `nix-store --realise`,
-except for `--arg` and `--attr` / `-A` which are passed to `nix-instantiate`.
+All options not listed here are passed to
+[`nix-store --realise`](nix-store/realise.md),
+except for `--arg` and `--attr` / `-A` which are passed to [`nix-instantiate`](nix-instantiate.md).
 
   - <span id="opt-no-out-link">[`--no-out-link`](#opt-no-out-link)<span>
 
@@ -69,6 +70,8 @@ except for `--arg` and `--attr` / `-A` which are passed to `nix-instantiate`.
     Change the name of the symlink to the output path created from
     `result` to *outlink*.
 
+{{#include ./status-build-failure.md}}
+
 {{#include ./opt-common.md}}
 
 {{#include ./env-common.md}}

doc/manual/src/command-ref/nix-channel.md

@@ -4,49 +4,63 @@
 
 # Synopsis
 
-`nix-channel` {`--add` url [*name*] | `--remove` *name* | `--list` | `--update` [*names…*] | `--rollback` [*generation*] }
+`nix-channel` {`--add` url [*name*] | `--remove` *name* | `--list` | `--update` [*names…*] | `--list-generations` | `--rollback` [*generation*] }
 
 # Description
 
-A Nix channel is a mechanism that allows you to automatically stay
-up-to-date with a set of pre-built Nix expressions. A Nix channel is
-just a URL that points to a place containing a set of Nix expressions.
+Channels are a mechanism for referencing remote Nix expressions and conveniently retrieving their latest version.
 
-To see the list of official NixOS channels, visit
-<https://nixos.org/channels>.
+The moving parts of channels are:
+- The official channels listed at <https://nixos.org/channels>
+- The user-specific list of [subscribed channels](#subscribed-channels)
+- The [downloaded channel contents](#channels)
+- The [Nix expression search path](@docroot@/command-ref/conf-file.md#conf-nix-path), set with the [`-I` option](#opt-i) or the [`NIX_PATH` environment variable](#env-NIX_PATH)
+
+> **Note**
+>
+> The state of a subscribed channel is external to the Nix expressions relying on it.
+> This may limit reproducibility.
+>
+> Dependencies on other Nix expressions can be declared explicitly with:
+> - [`fetchurl`](@docroot@/language/builtins.md#builtins-fetchurl), [`fetchTarball`](@docroot@/language/builtins.md#builtins-fetchTarball), or [`fetchGit`](@docroot@/language/builtins.md#builtins-fetchGit) in Nix expressions
+> - the [`-I` option](@docroot@/command-ref/opt-common.md#opt-I) in command line invocations
 
 This command has the following operations:
 
   - `--add` *url* \[*name*\]\
-    Adds a channel named *name* with URL *url* to the list of subscribed
-    channels. If *name* is omitted, it defaults to the last component of
-    *url*, with the suffixes `-stable` or `-unstable` removed.
+    Add a channel *name* located at *url* to the list of subscribed channels.
+    If *name* is omitted, default to the last component of *url*, with the suffixes `-stable` or `-unstable` removed.
+
+    > **Note**
+    >
+    > `--add` does not automatically perform an update.
+    > Use `--update` explicitly.
 
     A channel URL must point to a directory containing a file `nixexprs.tar.gz`.
     At the top level, that tarball must contain a single directory with a `default.nix` file that serves as the channel’s entry point.
 
   - `--remove` *name*\
-    Removes the channel named *name* from the list of subscribed
-    channels.
+    Remove the channel *name* from the list of subscribed channels.
 
   - `--list`\
-    Prints the names and URLs of all subscribed channels on standard
-    output.
+    Print the names and URLs of all subscribed channels on standard output.
 
   - `--update` \[*names*…\]\
-    Downloads the Nix expressions of all subscribed channels (or only
-    those included in *names* if specified) and makes them the default
-    for `nix-env` operations (by symlinking them from the directory
-    `~/.nix-defexpr`).
+    Download the Nix expressions of subscribed channels and create a new generation.
+    Update all channels if none is specified, and only those included in *names* otherwise.
+
+  - `--list-generations`\
+    Prints a list of all the current existing generations for the
+    channel profile.
+
+    Works the same way as
+    ```
+    nix-env --profile /nix/var/nix/profiles/per-user/$USER/channels --list-generations
+    ```
 
   - `--rollback` \[*generation*\]\
-    Reverts the previous call to `nix-channel
-                    --update`. Optionally, you can specify a specific channel generation
-    number to restore.
-
-Note that `--add` does not automatically perform an update.
-
-The list of subscribed channels is stored in `~/.nix-channels`.
+    Revert channels to the state before the last call to `nix-channel --update`.
+    Optionally, you can specify a specific channel *generation* number to restore.
 
 {{#include ./opt-common.md}}
 
@@ -60,23 +74,33 @@ The list of subscribed channels is stored in `~/.nix-channels`.
 
 # Examples
 
-To subscribe to the Nixpkgs channel and install the GNU Hello package:
+Subscribe to the Nixpkgs channel and run `hello` from the GNU Hello package:
 
 ```console
 $ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
+$ nix-channel --list
+nixpkgs https://nixos.org/channels/nixpkgs
 $ nix-channel --update
-$ nix-env --install --attr nixpkgs.hello
+$ nix-shell -p hello --run hello
+hello
 ```
 
-You can revert channel updates using `--rollback`:
+Revert channel updates using `--rollback`:
 
 ```console
-$ nix-instantiate --eval --expr '(import <nixpkgs> {}).lib.version'
-"14.04.527.0e935f1"
+$ nix-instantiate --eval '<nixpkgs>' --attr lib.version
+"22.11pre296212.530a53dcbc9"
 
 $ nix-channel --rollback
 switching from generation 483 to 482
 
-$ nix-instantiate --eval --expr '(import <nixpkgs> {}).lib.version'
-"14.04.526.dbadfad"
+$ nix-instantiate --eval '<nixpkgs>' --attr lib.version
+"22.11pre281526.d0419badfad"
+```
+
+Remove a channel:
+
+```console
+$ nix-channel --remove nixpkgs
+$ nix-channel --list
 ```

doc/manual/src/command-ref/nix-collect-garbage.md

@@ -1,6 +1,6 @@
 # Name
 
-`nix-collect-garbage` - delete unreachable store paths
+`nix-collect-garbage` - delete unreachable [store objects]
 
 # Synopsis
 
@@ -8,17 +8,57 @@
 
 # Description
 
-The command `nix-collect-garbage` is mostly an alias of [`nix-store
---gc`](@docroot@/command-ref/nix-store/gc.md), that is, it deletes all
-unreachable paths in the Nix store to clean up your system. However,
-it provides two additional options: `-d` (`--delete-old`), which
-deletes all old generations of all profiles in `/nix/var/nix/profiles`
-by invoking `nix-env --delete-generations old` on all profiles (of
-course, this makes rollbacks to previous configurations impossible);
-and `--delete-older-than` *period*, where period is a value such as
-`30d`, which deletes all generations older than the specified number
-of days in all profiles in `/nix/var/nix/profiles` (except for the
-generations that were active at that point in time).
+The command `nix-collect-garbage` is mostly an alias of [`nix-store --gc`](@docroot@/command-ref/nix-store/gc.md).
+That is, it deletes all unreachable [store objects] in the Nix store to clean up your system.
+
+However, it provides two additional options,
+[`--delete-old`](#opt-delete-old) and [`--delete-older-than`](#opt-delete-older-than),
+which also delete old [profiles], allowing potentially more [store objects] to be deleted because profiles are also garbage collection roots.
+These options are the equivalent of running
+[`nix-env --delete-generations`](@docroot@/command-ref/nix-env/delete-generations.md)
+with various augments on multiple profiles,
+prior to running `nix-collect-garbage` (or just `nix-store --gc`) without any flags.
+
+> **Note**
+>
+> Deleting previous configurations makes rollbacks to them impossible.
+
+These flags should be used with care, because they potentially delete generations of profiles used by other users on the system.
+
+## Locations searched for profiles
+
+`nix-collect-garbage` cannot know about all profiles; that information doesn't exist.
+Instead, it looks in a few locations, and acts on all profiles it finds there:
+
+1. The default profile locations as specified in the [profiles] section of the manual.
+
+2. > **NOTE**
+   >
+   > Not stable; subject to change
+   >
+   > Do not rely on this functionality; it just exists for migration purposes and is may change in the future.
+   > These deprecated paths remain a private implementation detail of Nix.
+
+   `$NIX_STATE_DIR/profiles` and `$NIX_STATE_DIR/profiles/per-user`.
+
+   With the exception of `$NIX_STATE_DIR/profiles/per-user/root` and `$NIX_STATE_DIR/profiles/default`, these directories are no longer used by other commands.
+   `nix-collect-garbage` looks there anyways in order to clean up profiles from older versions of Nix.
+
+# Options
+
+These options are for deleting old [profiles] prior to deleting unreachable [store objects].
+
+- <span id="opt-delete-old">[`--delete-old`](#opt-delete-old)</span> / `-d`\
+  Delete all old generations of profiles.
+
+  This is the equivalent of invoking `nix-env --delete-generations old` on each found profile.
+
+- <span id="opt-delete-older-than">[`--delete-older-than`](#opt-delete-older-than)</span> *period*\
+  Delete all generations of profiles older than the specified amount (except for the generations that were active at that point in time).
+  *period* is a value such as `30d`, which would mean 30 days.
+
+  This is the equivalent of invoking [`nix-env --delete-generations <period>`](@docroot@/command-ref/nix-env/delete-generations.md#generations-time) on each found profile.
+  See the documentation of that command for additional information about the *period* argument.
 
 {{#include ./opt-common.md}}
 
@@ -32,3 +72,6 @@ generations of each profile, do
 ```console
 $ nix-collect-garbage -d
 ```
+
+[profiles]: @docroot@/command-ref/files/profiles.md
+[store objects]: @docroot@/glossary.md#gloss-store-object

doc/manual/src/command-ref/nix-env/delete-generations.md

@@ -9,14 +9,47 @@
 # Description
 
 This operation deletes the specified generations of the current profile.
-The generations can be a list of generation numbers, the special value
-`old` to delete all non-current generations, a value such as `30d` to
-delete all generations older than the specified number of days (except
-for the generation that was active at that point in time), or a value
-such as `+5` to keep the last `5` generations ignoring any newer than
-current, e.g., if `30` is the current generation `+5` will delete
-generation `25` and all older generations. Periodically deleting old
-generations is important to make garbage collection effective.
+
+*generations* can be a one of the following:
+
+- <span id="generations-list">`<number>...`</span>:\
+  A list of generation numbers, each one a separate command-line argument.
+
+  Delete exactly the profile generations given by their generation number.
+  Deleting the current generation is not allowed.
+
+- The special value <span id="generations-old">`old`</span>
+
+  Delete all generations except the current one.
+
+  > **WARNING**
+  >
+  > Older *and newer* generations will be deleted by this operation.
+  >
+  > One might expect this to just delete older generations than the curent one, but that is only true if the current generation is also the latest.
+  > Because one can roll back to a previous generation, it is possible to have generations newer than the current one.
+  > They will also be deleted.
+
+- <span id="generations-time">`<number>d`</span>:\
+  The last *number* days
+
+  *Example*: `30d`
+
+  Delete all generations created more than *number* days ago, except the most recent one of them.
+  This allows rolling back to generations that were available within the specified period.
+
+- <span id="generations-count">`+<number>`</span>:\
+  The last *number* generations up to the present
+
+  *Example*: `+5`
+
+  Keep the last *number* generations, along with any newer than current.
+
+Periodically deleting old generations is important to make garbage collection
+effective.
+The is because profiles are also garbage collection roots — any [store object] reachable from a profile is "alive" and ineligible for deletion.
+
+[store object]: @docroot@/glossary.md#gloss-store-object
 
 {{#include ./opt-common.md}}
 
@@ -28,19 +61,35 @@ generations is important to make garbage collection effective.
 
 # Examples
 
+## Delete explicit generation numbers
+
 ```console
 $ nix-env --delete-generations 3 4 8
 ```
 
+Delete the generations numbered 3, 4, and 8, so long as the current active generation is not any of those.
+
+## Keep most-recent by count (number of generations)
+
 ```console
 $ nix-env --delete-generations +5
 ```
 
+Suppose `30` is the current generation, and we currently have generations numbered `20` through `32`.
+
+Then this command will delete generations `20` through `25` (`<= 30 - 5`),
+and keep generations `26` through `31` (`> 30 - 5`).
+
+## Keep most-recent by time (number of days)
+
 ```console
 $ nix-env --delete-generations 30d
 ```
 
+This command will delete all generations older than 30 days, except for the generation that was active 30 days ago (if it currently exists).
+
+## Delete all older
+
 ```console
 $ nix-env --profile other_profile --delete-generations old
 ```
-

doc/manual/src/command-ref/nix-env/install.md

@@ -14,23 +14,28 @@
 
 # Description
 
-The install operation creates a new user environment, based on the
-current generation of the active profile, to which a set of store paths
-described by *args* is added. The arguments *args* map to store paths in
-a number of possible ways:
+The install operation creates a new user environment.
+It is based on the current generation of the active [profile](@docroot@/command-ref/files/profiles.md), to which a set of [store paths] described by *args* is added.
 
-  - By default, *args* is a set of derivation names denoting derivations
-    in the active Nix expression. These are realised, and the resulting
-    output paths are installed. Currently installed derivations with a
-    name equal to the name of a derivation being added are removed
-    unless the option `--preserve-installed` is specified.
+[store paths]: @docroot@/glossary.md#gloss-store-path
+
+The arguments *args* map to store paths in a number of possible ways:
+
+
+  - By default, *args* is a set of [derivation] names denoting derivations in the [default Nix expression].
+    These are [realised], and the resulting output paths are installed.
+    Currently installed derivations with a name equal to the name of a derivation being added are removed unless the option `--preserve-installed` is specified.
+
+    [derivation]: @docroot@/glossary.md#gloss-derivation
+    [default Nix expression]: @docroot@/command-ref/files/default-nix-expression.md
+    [realised]: @docroot@/glossary.md#gloss-realise
 
     If there are multiple derivations matching a name in *args* that
     have the same name (e.g., `gcc-3.3.6` and `gcc-4.1.1`), then the
     derivation with the highest *priority* is used. A derivation can
     define a priority by declaring the `meta.priority` attribute. This
     attribute should be a number, with a higher value denoting a lower
-    priority. The default priority is `0`.
+    priority. The default priority is `5`.
 
     If there are multiple matching derivations with the same priority,
     then the derivation with the highest version will be installed.
@@ -40,44 +45,90 @@ a number of possible ways:
     gcc-3.3.6 gcc-4.1.1` will install both version of GCC (and will
     probably cause a user environment conflict\!).
 
-  - If `--attr` (`-A`) is specified, the arguments are *attribute
-    paths* that select attributes from the top-level Nix
-    expression. This is faster than using derivation names and
-    unambiguous. To find out the attribute paths of available
-    packages, use `nix-env --query --available --attr-path `.
+  - If [`--attr`](#opt-attr) / `-A` is specified, the arguments are *attribute paths* that select attributes from the [default Nix expression].
+    This is faster than using derivation names and unambiguous.
+    Show the attribute paths of available packages with [`nix-env --query`](./query.md):
+
+    ```console
+    nix-env --query --available --attr-path`
+    ```
 
   - If `--from-profile` *path* is given, *args* is a set of names
-    denoting installed store paths in the profile *path*. This is an
+    denoting installed [store paths] in the profile *path*. This is an
     easy way to copy user environment elements from one profile to
     another.
 
-  - If `--from-expression` is given, *args* are Nix
-    [functions](@docroot@/language/constructs.md#functions)
-    that are called with the active Nix expression as their single
-    argument. The derivations returned by those function calls are
-    installed. This allows derivations to be specified in an
-    unambiguous way, which is necessary if there are multiple
-    derivations with the same name.
+  - If `--from-expression` is given, *args* are [Nix language functions](@docroot@/language/constructs.md#functions) that are called with the [default Nix expression] as their single argument.
+    The derivations returned by those function calls are installed.
+    This allows derivations to be specified in an unambiguous way, which is necessary if there are multiple derivations with the same name.
 
-  - If *args* are [store derivations](@docroot@/glossary.md#gloss-store-derivation), then these are
-    [realised](@docroot@/command-ref/nix-store/realise.md), and the resulting output paths
-    are installed.
+  - If *args* are [store derivations](@docroot@/glossary.md#gloss-store-derivation), then these are [realised], and the resulting output paths are installed.
 
-  - If *args* are store paths that are not store derivations, then these
-    are [realised](@docroot@/command-ref/nix-store/realise.md) and installed.
+  - If *args* are [store paths] that are not store derivations, then these are [realised] and installed.
 
-  - By default all outputs are installed for each derivation. That can
-    be reduced by setting `meta.outputsToInstall`.
+  - By default all [outputs](@docroot@/language/derivations.md#attr-outputs) are installed for each [derivation].
+    This can be overridden by adding a `meta.outputsToInstall` attribute on the derivation listing a subset of the output names.
 
-# Flags
+    Example:
+
+    The file `example.nix` defines a derivation with two outputs `foo` and `bar`, each containing a file.
+
+    ```nix
+    # example.nix
+    let
+      pkgs = import <nixpkgs> {};
+      command = ''
+        ${pkgs.coreutils}/bin/mkdir -p $foo $bar
+        echo foo > $foo/foo-file
+        echo bar > $bar/bar-file
+      '';
+    in
+    derivation {
+      name = "example";
+      builder = "${pkgs.bash}/bin/bash";
+      args = [ "-c" command ];
+      outputs = [ "foo" "bar" ];
+      system = builtins.currentSystem;
+    }
+    ```
+
+    Installing from this Nix expression will make files from both outputs appear in the current profile.
+
+    ```console
+    $ nix-env --install --file example.nix
+    installing 'example'
+    $ ls ~/.nix-profile
+    foo-file
+    bar-file
+    manifest.nix
+    ```
+
+    Adding `meta.outputsToInstall` to that derivation will make `nix-env` only install files from the specified outputs.
+
+    ```nix
+    # example-outputs.nix
+    import ./example.nix // { meta.outputsToInstall = [ "bar" ]; }
+    ```
+
+    ```console
+    $ nix-env --install --file example-outputs.nix
+    installing 'example'
+    $ ls ~/.nix-profile
+    bar-file
+    manifest.nix
+    ```
+
+# Options
+
+  - `--prebuilt-only` / `-b`
 
-  - `--prebuilt-only` / `-b`\
     Use only derivations for which a substitute is registered, i.e.,
     there is a pre-built binary available that can be downloaded in lieu
     of building the derivation. Thus, no packages will be built from
     source.
 
-  - `--preserve-installed` / `-P`\
+  - `--preserve-installed` / `-P`
+
     Do not remove derivations with a name matching one of the
     derivations being installed. Usually, trying to have two versions of
     the same package installed in the same generation of a profile will
@@ -85,7 +136,8 @@ a number of possible ways:
     clashes between the two versions. However, this is not the case for
     all packages.
 
-  - `--remove-all` / `-r`\
+  - `--remove-all` / `-r`
+
     Remove all previously installed packages first. This is equivalent
     to running `nix-env --uninstall '.*'` first, except that everything happens
     in a single transaction.

doc/manual/src/command-ref/nix-prefetch-url.md

@@ -31,15 +31,18 @@ store already contains a file with the same hash and base name.
 Otherwise, the file is downloaded, and an error is signaled if the
 actual hash of the file does not match the specified hash.
 
-This command prints the hash on standard output. Additionally, if the
-option `--print-path` is used, the path of the downloaded file in the
-Nix store is also printed.
+This command prints the hash on standard output.
+The hash is printed using base-32 unless `--type md5` is specified,
+in which case it's printed using base-16.
+Additionally, if the option `--print-path` is used,
+the path of the downloaded file in the Nix store is also printed.
 
 # Options
 
   - `--type` *hashAlgo*\
-    Use the specified cryptographic hash algorithm, which can be one of
-    `md5`, `sha1`, `sha256`, and `sha512`.
+    Use the specified cryptographic hash algorithm,
+    which can be one of `md5`, `sha1`, `sha256`, and `sha512`.
+    The default is `sha256`.
 
   - `--print-path`\
     Print the store path of the downloaded file on standard output.

doc/manual/src/command-ref/nix-shell.md

@@ -235,14 +235,14 @@ package like Terraform:
 
 ```bash
 #! /usr/bin/env nix-shell
-#! nix-shell -i bash --packages "terraform.withPlugins (plugins: [ plugins.openstack ])"
+#! nix-shell -i bash --packages 'terraform.withPlugins (plugins: [ plugins.openstack ])'
 
 terraform apply
 ```
 
 > **Note**
 >
-> You must use double quotes (`"`) when passing a simple Nix expression
+> You must use single or double quotes (`'`, `"`) when passing a simple Nix expression
 > in a nix-shell shebang.
 
 Finally, using the merging of multiple nix-shell shebangs the following
@@ -251,7 +251,7 @@ branch):
 
 ```haskell
 #! /usr/bin/env nix-shell
-#! nix-shell -i runghc --packages "haskellPackages.ghcWithPackages (ps: [ps.download-curl ps.tagsoup])"
+#! nix-shell -i runghc --packages 'haskellPackages.ghcWithPackages (ps: [ps.download-curl ps.tagsoup])'
 #! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-20.03.tar.gz
 
 import Network.Curl.Download

doc/manual/src/command-ref/nix-store/query.md

@@ -5,8 +5,8 @@
 # Synopsis
 
 `nix-store` {`--query` | `-q`}
-  {`--outputs` | `--requisites` | `-R` | `--references` |
-  `--referrers` | `--referrers-closure` | `--deriver` | `-d` |
+  {`--outputs` | `--requisites` | `-R` | `--references` | `--referrers` |
+  `--referrers-closure` | `--deriver` | `-d` | `--valid-derivers` |
   `--graph` | `--tree` | `--binding` *name* | `-b` *name* | `--hash` |
   `--size` | `--roots`}
   [`--use-output`] [`-u`] [`--force-realise`] [`-f`]
@@ -82,13 +82,21 @@ symlink.
     in the Nix store that are dependent on *paths*.
 
   - `--deriver`; `-d`\
-    Prints the [deriver] of the store paths *paths*. If
+    Prints the [deriver] that was used to build the store paths *paths*. If
     the path has no deriver (e.g., if it is a source file), or if the
     deriver is not known (e.g., in the case of a binary-only
     deployment), the string `unknown-deriver` is printed.
+    The returned deriver is not guaranteed to exist in the local store, for
+    example when *paths* were substituted from a binary cache.
+    Use `--valid-derivers` instead to obtain valid paths only.
 
     [deriver]: ../../glossary.md#gloss-deriver
 
+  - `--valid-derivers`\
+    Prints a set of derivation files (`.drv`) which are supposed produce
+    said paths when realized. Might print nothing, for example for source paths
+    or paths subsituted from a binary cache.
+
   - `--graph`\
     Prints the references graph of the store paths *paths* in the format
     of the `dot` tool of AT\&T's [Graphviz

doc/manual/src/command-ref/nix-store/realise.md

@@ -1,6 +1,6 @@
 # Name
 
-`nix-store --realise` - realise specified store paths
+`nix-store --realise` - build or fetch store objects
 
 # Synopsis
 
@@ -8,33 +8,39 @@
 
 # Description
 
-The operation `--realise` essentially “builds” the specified store
-paths. Realisation is a somewhat overloaded term:
 
-  - If the store path is a *derivation*, realisation ensures that the
-    output paths of the derivation are [valid] (i.e.,
-    the output path and its closure exist in the file system). This
-    can be done in several ways. First, it is possible that the
-    outputs are already valid, in which case we are done
-    immediately. Otherwise, there may be [substitutes]
-    that produce the outputs (e.g., by downloading them). Finally, the
-    outputs can be produced by running the build task described
-    by the derivation.
+Each of *paths* is processed as follows:
 
-  - If the store path is not a derivation, realisation ensures that the
-    specified path is valid (i.e., it and its closure exist in the file
-    system). If the path is already valid, we are done immediately.
-    Otherwise, the path and any missing paths in its closure may be
-    produced through substitutes. If there are no (successful)
-    substitutes, realisation fails.
+- If the path leads to a [store derivation]:
+  1. If it is not [valid], substitute the store derivation file itself.
+  2. Realise its [output paths]:
+    - Try to fetch from [substituters] the [store objects] associated with the output paths in the store derivation's [closure].
+      - With [content-addressed derivations] (experimental):
+        Determine the output paths to realise by querying content-addressed realisation entries in the [Nix database].
+    - For any store paths that cannot be substituted, produce the required store objects:
+      1. Realise all outputs of the derivation's dependencies
+      2. Run the derivation's [`builder`](@docroot@/language/derivations.md#attr-builder) executable
+         <!-- TODO: Link to build process page #8888 -->
+- Otherwise, and if the path is not already valid: Try to fetch the associated [store objects] in the path's [closure] from [substituters].
 
+If no substitutes are available and no store derivation is given, realisation fails.
+
+[store paths]: @docroot@/glossary.md#gloss-store-path
 [valid]: @docroot@/glossary.md#gloss-validity
-[substitutes]: @docroot@/glossary.md#gloss-substitute
+[store derivation]: @docroot@/glossary.md#gloss-store-derivation
+[output paths]: @docroot@/glossary.md#gloss-output-path
+[store objects]: @docroot@/glossary.md#gloss-store-object
+[closure]: @docroot@/glossary.md#gloss-closure
+[substituters]: @docroot@/command-ref/conf-file.md#conf-substituters
+[content-addressed derivations]: @docroot@/contributing/experimental-features.md#xp-feature-ca-derivations
+[Nix database]: @docroot@/glossary.md#gloss-nix-database
 
-The output path of each derivation is printed on standard output. (For
-non-derivations argument, the argument itself is printed.)
+The resulting paths are printed on standard output.
+For non-derivation arguments, the argument itself is printed.
 
-The following flags are available:
+{{#include ../status-build-failure.md}}
+
+# Options
 
   - `--dry-run`\
     Print on standard error a description of what packages would be
@@ -54,37 +60,6 @@ The following flags are available:
     previous build, the new output path is left in
     `/nix/store/name.check.`
 
-Special exit codes:
-
-  - `100`\
-    Generic build failure, the builder process returned with a non-zero
-    exit code.
-
-  - `101`\
-    Build timeout, the build was aborted because it did not complete
-    within the specified `timeout`.
-
-  - `102`\
-    Hash mismatch, the build output was rejected because it does not
-    match the [`outputHash` attribute of the
-    derivation](@docroot@/language/advanced-attributes.md).
-
-  - `104`\
-    Not deterministic, the build succeeded in check mode but the
-    resulting output is not binary reproducible.
-
-With the `--keep-going` flag it's possible for multiple failures to
-occur, in this case the 1xx status codes are or combined using binary
-or.
-
-    1100100
-       ^^^^
-       |||`- timeout
-       ||`-- output hash mismatch
-       |`--- build failure
-       `---- not deterministic
-
-
 {{#include ./opt-common.md}}
 
 {{#include ../opt-common.md}}
@@ -96,8 +71,6 @@ or.
 This operation is typically used to build [store derivation]s produced by
 [`nix-instantiate`](@docroot@/command-ref/nix-instantiate.md):
 
-[store derivation]: @docroot@/glossary.md#gloss-store-derivation
-
 ```console
 $ nix-store --realise $(nix-instantiate ./test.nix)
 /nix/store/31axcgrlbfsxzmfff1gyj1bf62hvkby2-aterm-2.3.1

doc/manual/src/command-ref/opt-common-syn.md

@@ -1,57 +0,0 @@
-\--help
-
-\--version
-
-\--verbose
-
-\-v
-
-\--quiet
-
-\--log-format
-
-format
-
-\--no-build-output
-
-\-Q
-
-\--max-jobs
-
-\-j
-
-number
-
-\--cores
-
-number
-
-\--max-silent-time
-
-number
-
-\--timeout
-
-number
-
-\--keep-going
-
-\-k
-
-\--keep-failed
-
-\-K
-
-\--fallback
-
-\--readonly-mode
-
-\-I
-
-path
-
-\--option
-
-name
-
-value

doc/manual/src/command-ref/opt-common.md

@@ -2,217 +2,208 @@
 
 Most Nix commands accept the following command-line options:
 
-  - <span id="opt-help">[`--help`](#opt-help)</span>\
-    Prints out a summary of the command syntax and exits.
+- <span id="opt-help">[`--help`](#opt-help)</span>
 
-  - <span id="opt-version">[`--version`](#opt-version)</span>\
-    Prints out the Nix version number on standard output and exits.
+  Prints out a summary of the command syntax and exits.
 
-  - <span id="opt-verbose">[`--verbose`](#opt-verbose)</span> / `-v`\
-    Increases the level of verbosity of diagnostic messages printed on
-    standard error. For each Nix operation, the information printed on
-    standard output is well-defined; any diagnostic information is
-    printed on standard error, never on standard output.
+- <span id="opt-version">[`--version`](#opt-version)</span>
 
-    This option may be specified repeatedly. Currently, the following
-    verbosity levels exist:
+  Prints out the Nix version number on standard output and exits.
 
-      - 0\
-        “Errors only”: only print messages explaining why the Nix
-        invocation failed.
+- <span id="opt-verbose">[`--verbose`](#opt-verbose)</span> / `-v`
 
-      - 1\
-        “Informational”: print *useful* messages about what Nix is
-        doing. This is the default.
+  Increases the level of verbosity of diagnostic messages printed on standard error.
+  For each Nix operation, the information printed on standard output is well-defined;
+  any diagnostic information is printed on standard error, never on standard output.
 
-      - 2\
-        “Talkative”: print more informational messages.
+  This option may be specified repeatedly.
+  Currently, the following verbosity levels exist:
 
-      - 3\
-        “Chatty”: print even more informational messages.
+  - `0` “Errors only”
 
-      - 4\
-        “Debug”: print debug information.
+    Only print messages explaining why the Nix invocation failed.
 
-      - 5\
-        “Vomit”: print vast amounts of debug information.
+  - `1` “Informational”
 
-  - <span id="opt-quiet">[`--quiet`](#opt-quiet)</span>\
-    Decreases the level of verbosity of diagnostic messages printed on
-    standard error. This is the inverse option to `-v` / `--verbose`.
+    Print *useful* messages about what Nix is doing.
+    This is the default.
 
-    This option may be specified repeatedly. See the previous verbosity
-    levels list.
+  - `2` “Talkative”
 
-  - <span id="opt-log-format">[`--log-format`](#opt-log-format)</span> *format*\
-    This option can be used to change the output of the log format, with
-    *format* being one of:
+    Print more informational messages.
 
-      - raw\
-        This is the raw format, as outputted by nix-build.
+  - `3` “Chatty”
 
-      - internal-json\
-        Outputs the logs in a structured manner.
+    Print even more informational messages.
 
-        > **Warning**
-        >
-        > While the schema itself is relatively stable, the format of
-        > the error-messages (namely of the `msg`-field) can change
-        > between releases.
+  - `4` “Debug”
+   
+    Print debug information.
 
-      - bar\
-        Only display a progress bar during the builds.
+  - `5` “Vomit”
 
-      - bar-with-logs\
-        Display the raw logs, with the progress bar at the bottom.
+    Print vast amounts of debug information.
 
-  - <span id="opt-no-build-output">[`--no-build-output`](#opt-no-build-output)</span> / `-Q`\
-    By default, output written by builders to standard output and
-    standard error is echoed to the Nix command's standard error. This
-    option suppresses this behaviour. Note that the builder's standard
-    output and error are always written to a log file in
-    `prefix/nix/var/log/nix`.
+- <span id="opt-quiet">[`--quiet`](#opt-quiet)</span>
 
-  - <span id="opt-max-jobs">[`--max-jobs`](#opt-max-jobs)</span> / `-j` *number*\
-    Sets the maximum number of build jobs that Nix will perform in
-    parallel to the specified number. Specify `auto` to use the number
-    of CPUs in the system. The default is specified by the `max-jobs`
-    configuration setting, which itself defaults to `1`. A higher
-    value is useful on SMP systems or to exploit I/O latency.
+  Decreases the level of verbosity of diagnostic messages printed on standard error.
+  This is the inverse option to `-v` / `--verbose`.
 
-    Setting it to `0` disallows building on the local machine, which is
-    useful when you want builds to happen only on remote builders.
+  This option may be specified repeatedly.
+  See the previous verbosity levels list.
 
-  - <span id="opt-cores">[`--cores`](#opt-cores)</span>\
-    Sets the value of the `NIX_BUILD_CORES` environment variable in
-    the invocation of builders. Builders can use this variable at
-    their discretion to control the maximum amount of parallelism. For
-    instance, in Nixpkgs, if the derivation attribute
-    `enableParallelBuilding` is set to `true`, the builder passes the
-    `-jN` flag to GNU Make. It defaults to the value of the `cores`
-    configuration setting, if set, or `1` otherwise. The value `0`
-    means that the builder should use all available CPU cores in the
-    system.
+- <span id="opt-log-format">[`--log-format`](#opt-log-format)</span> *format*
 
-  - <span id="opt-max-silent-time">[`--max-silent-time`](#opt-max-silent-time)</span>\
-    Sets the maximum number of seconds that a builder can go without
-    producing any data on standard output or standard error. The
-    default is specified by the `max-silent-time` configuration
-    setting. `0` means no time-out.
+  This option can be used to change the output of the log format, with *format* being one of:
 
-  - <span id="opt-timeout">[`--timeout`](#opt-timeout)</span>\
-    Sets the maximum number of seconds that a builder can run. The
-    default is specified by the `timeout` configuration setting. `0`
-    means no timeout.
+  - `raw`
 
-  - <span id="opt-keep-going">[`--keep-going`](#opt-keep-going)</span> / `-k`\
-    Keep going in case of failed builds, to the greatest extent
-    possible. That is, if building an input of some derivation fails,
-    Nix will still build the other inputs, but not the derivation
-    itself. Without this option, Nix stops if any build fails (except
-    for builds of substitutes), possibly killing builds in progress (in
-    case of parallel or distributed builds).
+    This is the raw format, as outputted by nix-build.
 
-  - <span id="opt-keep-failed">[`--keep-failed`](#opt-keep-failed)</span> / `-K`\
-    Specifies that in case of a build failure, the temporary directory
-    (usually in `/tmp`) in which the build takes place should not be
-    deleted. The path of the build directory is printed as an
-    informational message.
+  - `internal-json`
 
-  - <span id="opt-fallback">[`--fallback`](#opt-fallback)</span>\
-    Whenever Nix attempts to build a derivation for which substitutes
-    are known for each output path, but realising the output paths
-    through the substitutes fails, fall back on building the derivation.
+    Outputs the logs in a structured manner.
 
-    The most common scenario in which this is useful is when we have
-    registered substitutes in order to perform binary distribution from,
-    say, a network repository. If the repository is down, the
-    realisation of the derivation will fail. When this option is
-    specified, Nix will build the derivation instead. Thus, installation
-    from binaries falls back on installation from source. This option is
-    not the default since it is generally not desirable for a transient
-    failure in obtaining the substitutes to lead to a full build from
-    source (with the related consumption of resources).
+    > **Warning**
+    >
+    > While the schema itself is relatively stable, the format of
+    > the error-messages (namely of the `msg`-field) can change
+    > between releases.
 
-  - <span id="opt-readonly-mode">[`--readonly-mode`](#opt-readonly-mode)</span>\
-    When this option is used, no attempt is made to open the Nix
-    database. Most Nix operations do need database access, so those
-    operations will fail.
+  - `bar`
 
-  - <span id="opt-arg">[`--arg`](#opt-arg)</span> *name* *value*\
-    This option is accepted by `nix-env`, `nix-instantiate`,
-    `nix-shell` and `nix-build`. When evaluating Nix expressions, the
-    expression evaluator will automatically try to call functions that
-    it encounters. It can automatically call functions for which every
-    argument has a [default
-    value](@docroot@/language/constructs.md#functions) (e.g.,
-    `{ argName ?  defaultValue }: ...`). With `--arg`, you can also
-    call functions that have arguments without a default value (or
-    override a default value). That is, if the evaluator encounters a
-    function with an argument named *name*, it will call it with value
-    *value*.
+    Only display a progress bar during the builds.
 
-    For instance, the top-level `default.nix` in Nixpkgs is actually a
-    function:
+  - `bar-with-logs`
 
-    ```nix
-    { # The system (e.g., `i686-linux') for which to build the packages.
-      system ? builtins.currentSystem
-      ...
-    }: ...
-    ```
+    Display the raw logs, with the progress bar at the bottom.
 
-    So if you call this Nix expression (e.g., when you do `nix-env --install --attr
-    pkgname`), the function will be called automatically using the
-    value [`builtins.currentSystem`](@docroot@/language/builtins.md) for
-    the `system` argument. You can override this using `--arg`, e.g.,
-    `nix-env --install --attr pkgname --arg system \"i686-freebsd\"`. (Note that
-    since the argument is a Nix string literal, you have to escape the
-    quotes.)
+- <span id="opt-no-build-output">[`--no-build-output`](#opt-no-build-output)</span> / `-Q`
 
-  - <span id="opt-argstr">[`--argstr`](#opt-argstr)</span> *name* *value*\
-    This option is like `--arg`, only the value is not a Nix
-    expression but a string. So instead of `--arg system
-    \"i686-linux\"` (the outer quotes are to keep the shell happy) you
-    can say `--argstr system i686-linux`.
+  By default, output written by builders to standard output and standard error is echoed to the Nix command's standard error.
+  This option suppresses this behaviour.
+  Note that the builder's standard output and error are always written to a log file in `prefix/nix/var/log/nix`.
 
-  - <span id="opt-attr">[`--attr`](#opt-attr)</span> / `-A` *attrPath*\
-    Select an attribute from the top-level Nix expression being
-    evaluated. (`nix-env`, `nix-instantiate`, `nix-build` and
-    `nix-shell` only.) The *attribute path* *attrPath* is a sequence
-    of attribute names separated by dots. For instance, given a
-    top-level Nix expression *e*, the attribute path `xorg.xorgserver`
-    would cause the expression `e.xorg.xorgserver` to be used. See
-    [`nix-env --install`](@docroot@/command-ref/nix-env/install.md) for some
-    concrete examples.
+- <span id="opt-max-jobs">[`--max-jobs`](#opt-max-jobs)</span> / `-j` *number*
 
-    In addition to attribute names, you can also specify array indices.
-    For instance, the attribute path `foo.3.bar` selects the `bar`
-    attribute of the fourth element of the array in the `foo` attribute
-    of the top-level expression.
+  Sets the maximum number of build jobs that Nix will perform in parallel to the specified number.
+  Specify `auto` to use the number of CPUs in the system.
+  The default is specified by the `max-jobs` configuration setting, which itself defaults to `1`.
+  A higher value is useful on SMP systems or to exploit I/O latency.
 
-  - <span id="opt-expr">[`--expr`](#opt-expr)</span> / `-E`\
-    Interpret the command line arguments as a list of Nix expressions to
-    be parsed and evaluated, rather than as a list of file names of Nix
-    expressions. (`nix-instantiate`, `nix-build` and `nix-shell` only.)
+  Setting it to `0` disallows building on the local machine, which is useful when you want builds to happen only on remote builders.
 
-    For `nix-shell`, this option is commonly used to give you a shell in
-    which you can build the packages returned by the expression. If you
-    want to get a shell which contain the *built* packages ready for
-    use, give your expression to the `nix-shell --packages ` convenience flag
-    instead.
+- <span id="opt-cores">[`--cores`](#opt-cores)</span>
 
-  - <span id="opt-I">[`-I`](#opt-I)</span> *path*\
-    Add an entry to the [Nix expression search path](@docroot@/command-ref/conf-file.md#conf-nix-path).
-    This option may be given multiple times.
-    Paths added through `-I` take precedence over [`NIX_PATH`](@docroot@/command-ref/env-common.md#env-NIX_PATH).
+  Sets the value of the `NIX_BUILD_CORES` environment variable in the invocation of builders.
+  Builders can use this variable at their discretion to control the maximum amount of parallelism.
+  For instance, in Nixpkgs, if the derivation attribute `enableParallelBuilding` is set to `true`, the builder passes the `-jN` flag to GNU Make.
+  It defaults to the value of the `cores` configuration setting, if set, or `1` otherwise.
+  The value `0` means that the builder should use all available CPU cores in the system.
 
-  - <span id="opt-option">[`--option`](#opt-option)</span> *name* *value*\
-    Set the Nix configuration option *name* to *value*. This overrides
-    settings in the Nix configuration file (see nix.conf5).
+- <span id="opt-max-silent-time">[`--max-silent-time`](#opt-max-silent-time)</span>
 
-  - <span id="opt-repair">[`--repair`](#opt-repair)</span>\
-    Fix corrupted or missing store paths by redownloading or rebuilding
-    them. Note that this is slow because it requires computing a
-    cryptographic hash of the contents of every path in the closure of
-    the build. Also note the warning under `nix-store --repair-path`.
+  Sets the maximum number of seconds that a builder can go without producing any data on standard output or standard error.
+  The default is specified by the `max-silent-time` configuration setting.
+  `0` means no time-out.
+
+- <span id="opt-timeout">[`--timeout`](#opt-timeout)</span>
+
+  Sets the maximum number of seconds that a builder can run.
+  The default is specified by the `timeout` configuration setting.
+  `0` means no timeout.
+
+- <span id="opt-keep-going">[`--keep-going`](#opt-keep-going)</span> / `-k`
+
+  Keep going in case of failed builds, to the greatest extent possible.
+  That is, if building an input of some derivation fails, Nix will still build the other inputs, but not the derivation itself.
+  Without this option, Nix stops if any build fails (except for builds of substitutes), possibly killing builds in progress (in case of parallel or distributed builds).
+
+- <span id="opt-keep-failed">[`--keep-failed`](#opt-keep-failed)</span> / `-K`
+
+  Specifies that in case of a build failure, the temporary directory (usually in `/tmp`) in which the build takes place should not be deleted.
+  The path of the build directory is printed as an informational message.
+
+- <span id="opt-fallback">[`--fallback`](#opt-fallback)</span>
+
+  Whenever Nix attempts to build a derivation for which substitutes are known for each output path, but realising the output paths through the substitutes fails, fall back on building the derivation.
+
+  The most common scenario in which this is useful is when we have registered substitutes in order to perform binary distribution from, say, a network repository.
+  If the repository is down, the realisation of the derivation will fail.
+  When this option is specified, Nix will build the derivation instead.
+  Thus, installation from binaries falls back on installation from source.
+  This option is not the default since it is generally not desirable for a transient failure in obtaining the substitutes to lead to a full build from source (with the related consumption of resources).
+
+- <span id="opt-readonly-mode">[`--readonly-mode`](#opt-readonly-mode)</span>
+
+  When this option is used, no attempt is made to open the Nix database.
+  Most Nix operations do need database access, so those operations will fail.
+
+- <span id="opt-arg">[`--arg`](#opt-arg)</span> *name* *value*
+
+  This option is accepted by `nix-env`, `nix-instantiate`, `nix-shell` and `nix-build`.
+  When evaluating Nix expressions, the expression evaluator will automatically try to call functions that it encounters.
+  It can automatically call functions for which every argument has a [default value](@docroot@/language/constructs.md#functions) (e.g., `{ argName ?  defaultValue }: ...`).
+
+  With `--arg`, you can also call functions that have arguments without a default value (or override a default value).
+  That is, if the evaluator encounters a function with an argument named *name*, it will call it with value *value*.
+
+  For instance, the top-level `default.nix` in Nixpkgs is actually a function:
+
+  ```nix
+  { # The system (e.g., `i686-linux') for which to build the packages.
+    system ? builtins.currentSystem
+    ...
+  }: ...
+  ```
+
+  So if you call this Nix expression (e.g., when you do `nix-env --install --attr pkgname`), the function will be called automatically using the value [`builtins.currentSystem`](@docroot@/language/builtins.md) for the `system` argument.
+  You can override this using `--arg`, e.g., `nix-env --install --attr pkgname --arg system \"i686-freebsd\"`.
+  (Note that since the argument is a Nix string literal, you have to escape the quotes.)
+
+- <span id="opt-argstr">[`--argstr`](#opt-argstr)</span> *name* *value*
+
+  This option is like `--arg`, only the value is not a Nix expression but a string.
+  So instead of `--arg system \"i686-linux\"` (the outer quotes are to keep the shell happy) you can say `--argstr system i686-linux`.
+
+- <span id="opt-attr">[`--attr`](#opt-attr)</span> / `-A` *attrPath*
+
+  Select an attribute from the top-level Nix expression being evaluated.
+  (`nix-env`, `nix-instantiate`, `nix-build` and `nix-shell` only.)
+  The *attribute path* *attrPath* is a sequence of attribute names separated by dots.
+  For instance, given a top-level Nix expression *e*, the attribute path `xorg.xorgserver` would cause the expression `e.xorg.xorgserver` to be used.
+  See [`nix-env --install`](@docroot@/command-ref/nix-env/install.md) for some concrete examples.
+
+  In addition to attribute names, you can also specify array indices.
+  For instance, the attribute path `foo.3.bar` selects the `bar`
+  attribute of the fourth element of the array in the `foo` attribute
+  of the top-level expression.
+
+- <span id="opt-expr">[`--expr`](#opt-expr)</span> / `-E`
+
+  Interpret the command line arguments as a list of Nix expressions to be parsed and evaluated, rather than as a list of file names of Nix expressions.
+  (`nix-instantiate`, `nix-build` and `nix-shell` only.)
+
+  For `nix-shell`, this option is commonly used to give you a shell in which you can build the packages returned by the expression.
+  If you want to get a shell which contain the *built* packages ready for use, give your expression to the `nix-shell --packages ` convenience flag instead.
+
+- <span id="opt-I">[`-I`](#opt-I)</span> *path*
+
+  Add an entry to the [Nix expression search path](@docroot@/command-ref/conf-file.md#conf-nix-path).
+  This option may be given multiple times.
+  Paths added through `-I` take precedence over [`NIX_PATH`](@docroot@/command-ref/env-common.md#env-NIX_PATH).
+
+- <span id="opt-option">[`--option`](#opt-option)</span> *name* *value*
+
+  Set the Nix configuration option *name* to *value*.
+  This overrides settings in the Nix configuration file (see nix.conf5).
+
+- <span id="opt-repair">[`--repair`](#opt-repair)</span>
+
+  Fix corrupted or missing store paths by redownloading or rebuilding them.
+  Note that this is slow because it requires computing a cryptographic hash of the contents of every path in the closure of the build.
+  Also note the warning under `nix-store --repair-path`.
+
+> **Note**
+>
+> See [`man nix.conf`](@docroot@/command-ref/conf-file.md#command-line-flags) for overriding configuration settings with command line flags.

doc/manual/src/command-ref/opt-inst-syn.md

@@ -1,15 +0,0 @@
-\--prebuilt-only
-
-\-b
-
-\--attr
-
-\-A
-
-\--from-expression
-
-\-E
-
-\--from-profile
-
-path

doc/manual/src/command-ref/status-build-failure.md

@@ -0,0 +1,34 @@
+# Special exit codes for build failure
+
+1xx status codes are used when requested builds failed.
+The following codes are in use:
+
+- `100` Generic build failure
+
+  The builder process returned with a non-zero exit code.
+
+- `101` Build timeout
+
+  The build was aborted because it did not complete within the specified `timeout`.
+
+- `102` Hash mismatch
+
+  The build output was rejected because it does not match the
+  [`outputHash` attribute of the derivation](@docroot@/language/advanced-attributes.md).
+
+- `104` Not deterministic
+
+  The build succeeded in check mode but the resulting output is not binary reproducible.
+
+With the `--keep-going` flag it's possible for multiple failures to occur.
+In this case the 1xx status codes are or combined using
+[bitwise OR](https://en.wikipedia.org/wiki/Bitwise_operation#OR).
+
+```
+0b1100100
+     ^^^^
+     |||`- timeout
+     ||`-- output hash mismatch
+     |`--- build failure
+     `---- not deterministic
+```

doc/manual/src/contributing/contributing.md

@@ -1 +1,8 @@
-# Contributing
+# Development
+
+Nix is developed on GitHub.
+Check the [contributing guide](https://github.com/NixOS/nix/blob/master/CONTRIBUTING.md) if you want to get involved.
+
+This chapter is a collection of guides for making changes to the code and documentation.
+
+If you're not sure where to start, try to [compile Nix from source](./hacking.md) and consider [making improvements to documentation](./documentation.md).

doc/manual/src/contributing/cxx.md

@@ -0,0 +1,28 @@
+# C++ style guide
+
+Some miscellaneous notes on how we write C++.
+Formatting we hope to eventually normalize automatically, so this section is free to just discuss higher-level concerns.
+
+## The `*-impl.hh` pattern
+
+Let's start with some background info first.
+Headers, are supposed to contain declarations, not definitions.
+This allows us to change a definition without changing the declaration, and have a very small rebuild during development.
+Templates, however, need to be specialized to use-sites.
+Absent fancier techniques, templates require that the definition, not just mere declaration, must be available at use-sites in order to make that specialization on the fly as part of compiling those use-sites.
+Making definitions available like that means putting them in headers, but that is unfortunately means we get all the extra rebuilds we want to avoid by just putting declarations there as described above.
+
+The `*-impl.hh` pattern is a ham-fisted partial solution to this problem.
+It constitutes:
+
+- Declaring items only in the main `foo.hh`, including templates.
+
+- Putting template definitions in a companion `foo-impl.hh` header.
+
+Most C++ developers would accompany this by having `foo.hh` include `foo-impl.hh`, to ensure any file getting the template declarations also got the template definitions.
+But we've found not doing this has some benefits and fewer than imagined downsides.
+The fact remains that headers are rarely as minimal as they could be;
+there is often code that needs declarations from the headers but not the templates within them.
+With our pattern where `foo.hh` doesn't include `foo-impl.hh`, that means they can just include `foo.hh`
+Code that needs both just includes `foo.hh` and `foo-impl.hh`.
+This does make linking error possible where something forgets to include `foo-impl.hh` that needs it, but those are build-time only as easy to fix.

doc/manual/src/contributing/documentation.md

@@ -0,0 +1,210 @@
+# Contributing documentation
+
+Improvements to documentation are very much appreciated, and a good way to start out with contributing to Nix.
+
+This is how you can help:
+- Address [open issues with documentation](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+label%3Adocumentation)
+- Review [pull requests concerning documentation](https://github.com/NixOS/nix/pulls?q=is%3Apr+is%3Aopen+label%3Adocumentation)
+
+Incremental refactorings of the documentation build setup to make it faster or easier to understand and maintain are also welcome.
+
+## Building the manual
+
+Build the manual from scratch:
+
+```console
+nix-build $(nix-instantiate)'!doc'
+```
+
+or
+
+```console
+nix build .#^doc
+```
+
+and open `./result-doc/share/doc/nix/manual/index.html`.
+
+To build the manual incrementally, [enter the development shell](./hacking.md) and run:
+
+```console
+make manual-html -j $NIX_BUILD_CORES
+```
+
+and open `./outputs/out/share/doc/nix/manual/language/index.html`.
+
+In order to reflect changes to the [Makefile for the manual], clear all generated files before re-building:
+
+[Makefile for the manual]: https://github.com/NixOS/nix/blob/master/doc/manual/local.mk
+
+```console
+rm $(git ls-files doc/manual/ -o | grep -F '.md') && rmdir doc/manual/src/command-ref/new-cli && make manual-html -j $NIX_BUILD_CORES
+```
+
+## Style guide
+
+The goal of this style guide is to make it such that
+- The manual is easy to search and skim for relevant information
+- Documentation sources are easy to edit
+- Changes to documentation are easy to review
+
+You will notice that this is not implemented consistently yet.
+Please follow the guide when making additions or changes to existing documentation.
+Do not make sweeping changes, unless they are programmatic and can be validated easily.
+
+### Language
+
+This manual is [reference documentation](https://diataxis.fr/reference/).
+The typical usage pattern is to look up isolated pieces of information.
+It should therefore aim to be correct, consistent, complete, and easy to navigate at a glance.
+
+- Aim for clarity and brevity.
+
+  Please take the time to read the [plain language guidelines](https://www.plainlanguage.gov/guidelines/) for details.
+
+- Describe the subject factually.
+
+  In particular, do not make value judgements or recommendations.
+  Check the code or add tests if in doubt.
+
+- Provide complete, minimal examples, and explain them.
+
+  Readers should be able to try examples verbatim and get the same results as shown in the manual.
+  Always describe in words what a given example does.
+
+  Non-trivial examples may need additional explanation, especially if they use concepts from outside the given context.
+
+- Always explain code examples in the text.
+
+  Use comments in code samples very sparingly, for instance to highlight a particular aspect.
+  Readers tend to glance over large amounts of code when scanning for information.
+
+  Especially beginners will likely find reading more complex-looking code strenuous and may therefore avoid it altogether.
+
+  If a code sample appears to require a lot of inline explanation, consider replacing it with a simpler one.
+  If that's not possible, break the example down into multiple parts, explain them separately, and then show the combined result at the end.
+  This should be a last resort, as that would amount to writing a [tutorial](https://diataxis.fr/tutorials/) on the given subject.
+
+- Use British English.
+
+  This is a somewhat arbitrary choice to force consistency, and accounts for the fact that a majority of Nix users and developers are from Europe.
+
+### Links and anchors
+
+Reference documentation must be readable in arbitrary order.
+Readers cannot be expected to have any particular prerequisite knowledge about Nix.
+While the table of contents can provide guidance and full-text search can help, they are most likely to find what they need by following sensible cross-references.
+
+- Link to technical terms
+
+  When mentioning Nix-specific concepts, commands, options, settings, etc., link to appropriate documentation.
+  Also link to external tools or concepts, especially if their meaning may be ambiguous.
+  You may also want to link to definitions of less common technical terms.
+
+  Then readers won't have to actively search for definitions and are more likely to discover relevant information on their own.
+
+  > **Note**
+  >
+  > `man` and `--help` pages don't display links.
+  > Use appropriate link texts such that readers of terminal output can infer search terms.
+
+- Do not break existing URLs between releases.
+
+  There are countless links in the wild pointing to old versions of the manual.
+  We want people to find up-to-date documentation when following popular advice.
+
+  - When moving files, update [redirects on nixos.org](https://github.com/NixOS/nixos-homepage/blob/master/netlify.toml).
+
+    This is especially important when moving information out of the Nix manual to other resources.
+
+  - When changing anchors, update [client-side redirects](https://github.com/NixOS/nix/blob/master/doc/manual/redirects.js)
+
+  The current setup is cumbersome, and help making better automation is appreciated.
+
+The build checks for broken internal links with.
+This happens late in the process, so [building the whole manual](#building-the-manual) is not suitable for iterating quickly.
+[`mdbook-linkcheck`] does not implement checking [URI fragments] yet.
+
+[`mdbook-linkcheck`]: https://github.com/Michael-F-Bryan/mdbook-linkcheck
+[URI fragments]: https://en.wikipedia.org/wiki/URI_fragment
+
+### Markdown conventions
+
+The manual is written in markdown, and rendered with [mdBook](https://github.com/rust-lang/mdBook) for the web and with [lowdown](https://github.com/kristapsdz/lowdown) for `man` pages and `--help` output.
+
+For supported markdown features, refer to:
+- [mdBook documentation](https://rust-lang.github.io/mdBook/format/markdown.html)
+- [lowdown documentation](https://kristaps.bsd.lv/lowdown/)
+
+Please observe these guidelines to ease reviews:
+
+- Write one sentence per line.
+
+  This makes long sentences immediately visible, and makes it easier to review changes and make direct suggestions.
+
+- Use reference links – sparingly – to ease source readability.
+  Put definitions close to their first use.
+
+  Example:
+
+  ```
+  A [store object] contains a [file system object] and [references] to other store objects.
+
+  [store object]: @docroot@/glossary.md#gloss-store-object
+  [file system object]: @docroot@/architecture/file-system-object.md
+  [references]: @docroot@/glossary.md#gloss-reference
+  ```
+
+- Use admonitions of the following form:
+
+  ```
+  > **Note**
+  >
+  > This is a note.
+  ```
+
+  Highlight examples as such:
+
+  ````
+  > **Example**
+  >
+  > ```console
+  > $ nix --version
+  > ```
+  ````
+
+  Highlight syntax definiions as such, using [EBNF](https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_form) notation:
+
+  ````
+  > **Syntax**
+  >
+  > *attribute-set* = `{` [ *attribute-name* `=` *expression* `;` ... ] `}`
+  ````
+
+### The `@docroot@` variable
+
+`@docroot@` provides a base path for links that occur in reusable snippets or other documentation that doesn't have a base path of its own.
+
+If a broken link occurs in a snippet that was inserted into multiple generated files in different directories, use `@docroot@` to reference the `doc/manual/src` directory.
+
+If the `@docroot@` literal appears in an error message from the [`mdbook-linkcheck`] tool, the `@docroot@` replacement needs to be applied to the generated source file that mentions it.
+See existing `@docroot@` logic in the [Makefile for the manual].
+Regular markdown files used for the manual have a base path of their own and they can use relative paths instead of `@docroot@`.
+
+## API documentation
+
+[Doxygen API documentation] is available online.
+You can also build and view it yourself:
+
+[Doxygen API documentation]: https://hydra.nixos.org/job/nix/master/internal-api-docs/latest/download-by-type/doc/internal-api-docs
+
+```console
+# nix build .#hydraJobs.internal-api-docs
+# xdg-open ./result/share/doc/nix/internal-api/html/index.html
+```
+
+or inside `nix-shell` or `nix develop`:
+
+```
+# make internal-api-html
+# xdg-open ./outputs/doc/share/doc/nix/internal-api/html/index.html
+```

doc/manual/src/contributing/hacking.md

@@ -12,14 +12,15 @@ The following instructions assume you already have some version of Nix installed
 
 [installation instructions]: ../installation/installation.md
 
-## Nix with flakes
+## Building Nix with flakes
 
-This section assumes you are using Nix with [flakes] enabled. See the [next section](#classic-nix) for equivalent instructions which don't require flakes.
+This section assumes you are using Nix with the [`flakes`] and [`nix-command`] experimental features enabled.
+See the [Building Nix](#building-nix) section for equivalent instructions using stable Nix interfaces.
 
-[flakes]: ../command-ref/new-cli/nix3-flake.md#description
+[`flakes`]: @docroot@/contributing/experimental-features.md#xp-feature-flakes
+[`nix-command`]: @docroot@/contributing/experimental-features.md#xp-nix-command
 
-To build all dependencies and start a shell in which all environment
-variables are set up so that those dependencies can be found:
+To build all dependencies and start a shell in which all environment variables are set up so that those dependencies can be found:
 
 ```console
 $ nix develop
@@ -41,8 +42,8 @@ $ nix develop .#native-clang11StdenvPackages
 To build Nix itself in this shell:
 
 ```console
-[nix-shell]$ ./bootstrap.sh
-[nix-shell]$ ./configure $configureFlags --prefix=$(pwd)/outputs/out
+[nix-shell]$ autoreconfPhase
+[nix-shell]$ configurePhase
 [nix-shell]$ make -j $NIX_BUILD_CORES
 ```
 
@@ -55,20 +56,17 @@ To install it in `$(pwd)/outputs` and test it:
 nix (Nix) 2.12
 ```
 
-To build a release version of Nix:
+To build a release version of Nix for the current operating system and CPU architecture:
 
 ```console
 $ nix build
 ```
 
-You can also build Nix for one of the [supported target platforms](#target-platforms).
+You can also build Nix for one of the [supported platforms](#platforms).
 
-## Classic Nix
+## Building Nix
 
-This section is for Nix without [flakes].
-
-To build all dependencies and start a shell in which all environment
-variables are set up so that those dependencies can be found:
+To build all dependencies and start a shell in which all environment variables are set up so that those dependencies can be found:
 
 ```console
 $ nix-shell
@@ -88,7 +86,7 @@ $ nix-shell --attr devShells.x86_64-linux.native-clang11StdenvPackages
 To build Nix itself in this shell:
 
 ```console
-[nix-shell]$ ./bootstrap.sh
+[nix-shell]$ autoreconfPhase
 [nix-shell]$ ./configure $configureFlags --prefix=$(pwd)/outputs/out
 [nix-shell]$ make -j $NIX_BUILD_CORES
 ```
@@ -102,51 +100,82 @@ To install it in `$(pwd)/outputs` and test it:
 nix (Nix) 2.12
 ```
 
-To build Nix for the current operating system and CPU architecture use
+To build a release version of Nix for the current operating system and CPU architecture:
 
 ```console
 $ nix-build
 ```
 
-You can also build Nix for one of the [supported target platforms](#target-platforms).
+You can also build Nix for one of the [supported platforms](#platforms).
 
 ## Platforms
 
-As specified in [`flake.nix`], Nix can be built for various platforms:
-
-- `aarch64-linux`
-- `i686-linux`
-- `x86_64-darwin`
-- `x86_64-linux`
+Nix can be built for various platforms, as specified in [`flake.nix`]:
 
 [`flake.nix`]: https://github.com/nixos/nix/blob/master/flake.nix
 
+- `x86_64-linux`
+- `x86_64-darwin`
+- `i686-linux`
+- `aarch64-linux`
+- `aarch64-darwin`
+- `armv6l-linux`
+- `armv7l-linux`
+
 In order to build Nix for a different platform than the one you're currently
-on, you need to have some way for your system Nix to build code for that
-platform. Common solutions include [remote builders] and [binfmt emulation]
+on, you need a way for your current Nix installation to build code for that
+platform. Common solutions include [remote builders] and [binary format emulation]
 (only supported on NixOS).
 
 [remote builders]: ../advanced-topics/distributed-builds.md
-[binfmt emulation]: https://nixos.org/manual/nixos/stable/options.html#opt-boot.binfmt.emulatedSystems
+[binary format emulation]: https://nixos.org/manual/nixos/stable/options.html#opt-boot.binfmt.emulatedSystems
 
-These solutions let Nix perform builds as if you're on the native platform, so
-executing the build is as simple as
-
-```console
-$ nix build .#packages.aarch64-linux.default
-```
-
-for flake-enabled Nix, or
+Given such a setup, executing the build only requires selecting the respective attribute.
+For example, to compile for `aarch64-linux`:
 
 ```console
 $ nix-build --attr packages.aarch64-linux.default
 ```
 
-for classic Nix.
+or for Nix with the [`flakes`] and [`nix-command`] experimental features enabled:
 
-You can use any of the other supported platforms in place of `aarch64-linux`.
+```console
+$ nix build .#packages.aarch64-linux.default
+```
 
-Cross-compiled builds are available for ARMv6 and ARMv7, and Nix on unsupported platforms can be bootstrapped by adding more `crossSystems` in `flake.nix`.
+Cross-compiled builds are available for ARMv6 (`armv6l-linux`) and ARMv7 (`armv7l-linux`).
+Add more [system types](#system-type) to `crossSystems` in `flake.nix` to bootstrap Nix on unsupported platforms.
+
+## System type
+
+Nix uses a string with he following format to identify the *system type* or *platform* it runs on:
+
+```
+<cpu>-<os>[-<abi>]
+```
+
+It is set when Nix is compiled for the given system, and based on the output of [`config.guess`](https://github.com/nixos/nix/blob/master/config/config.guess) ([upstream](https://git.savannah.gnu.org/cgit/config.git/tree/config.guess)):
+
+```
+<cpu>-<vendor>-<os>[<version>][-<abi>]
+```
+
+When Nix is built such that `./configure` is passed any of the `--host`, `--build`, `--target` options, the value is based on the output of [`config.sub`](https://github.com/nixos/nix/blob/master/config/config.sub) ([upstream](https://git.savannah.gnu.org/cgit/config.git/tree/config.sub)):
+
+```
+<cpu>-<vendor>[-<kernel>]-<os>
+```
+
+For historic reasons and backward-compatibility, some CPU and OS identifiers are translated from the GNU Autotools naming convention in [`configure.ac`](https://github.com/nixos/nix/blob/master/configure.ac) as follows:
+
+| `config.guess`             | Nix                 |
+|----------------------------|---------------------|
+| `amd64`                    | `x86_64`            |
+| `i*86`                     | `i686`              |
+| `arm6`                     | `arm6l`             |
+| `arm7`                     | `arm7l`             |
+| `linux-gnu*`               | `linux`             |
+| `linux-musl*`              | `linux`             |
 
 ## Compilation environments
 
@@ -181,7 +210,7 @@ See [supported compilation environments](#compilation-environments) and instruct
 To use the LSP with your editor, you first need to [set up `clangd`](https://clangd.llvm.org/installation#project-setup) by running:
 
 ```console
-make clean && bear -- make -j$NIX_BUILD_CORES install
+make clean && bear -- make -j$NIX_BUILD_CORES default check install
 ```
 
 Configure your editor to use the `clangd` from the shell, either by running it inside the development shell, or by using [nix-direnv](https://github.com/nix-community/nix-direnv) and [the appropriate editor plugin](https://github.com/direnv/direnv/wiki#editor-integration).
@@ -191,233 +220,3 @@ Configure your editor to use the `clangd` from the shell, either by running it i
 > For some editors (e.g. Visual Studio Code), you may need to install a [special extension](https://open-vsx.org/extension/llvm-vs-code-extensions/vscode-clangd) for the editor to interact with `clangd`.
 > Some other editors (e.g. Emacs, Vim) need a plugin to support LSP servers in general (e.g. [lsp-mode](https://github.com/emacs-lsp/lsp-mode) for Emacs and [vim-lsp](https://github.com/prabirshrestha/vim-lsp) for vim).
 > Editor-specific setup is typically opinionated, so we will not cover it here in more detail.
-
-## Running tests
-
-### Unit-tests
-
-The unit-tests for each Nix library (`libexpr`, `libstore`, etc..) are defined
-under `src/{library_name}/tests` using the
-[googletest](https://google.github.io/googletest/) and
-[rapidcheck](https://github.com/emil-e/rapidcheck) frameworks.
-
-You can run the whole testsuite with `make check`, or the tests for a specific component with `make libfoo-tests_RUN`. Finer-grained filtering is also possible using the [--gtest_filter](https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests) command-line option.
-
-### Functional tests
-
-The functional tests reside under the `tests` directory and are listed in `tests/local.mk`.
-Each test is a bash script.
-
-The whole test suite can be run with:
-
-```shell-session
-$ make install && make installcheck
-ran test tests/foo.sh... [PASS]
-ran test tests/bar.sh... [PASS]
-...
-```
-
-Individual tests can be run with `make`:
-
-```shell-session
-$ make tests/${testName}.sh.test
-ran test tests/${testName}.sh... [PASS]
-```
-
-or without `make`:
-
-```shell-session
-$ ./mk/run-test.sh tests/${testName}.sh
-ran test tests/${testName}.sh... [PASS]
-```
-
-To see the complete output, one can also run:
-
-```shell-session
-$ ./mk/debug-test.sh tests/${testName}.sh
-+ foo
-output from foo
-+ bar
-output from bar
-...
-```
-
-The test script will then be traced with `set -x` and the output displayed as it happens, regardless of whether the test succeeds or fails.
-
-#### Debugging failing functional tests
-
-When a functional test fails, it usually does so somewhere in the middle of the script.
-
-To figure out what's wrong, it is convenient to run the test regularly up to the failing `nix` command, and then run that command with a debugger like GDB.
-
-For example, if the script looks like:
-
-```bash
-foo
-nix blah blub
-bar
-```
-edit it like so:
-
-```diff
- foo
--nix blah blub
-+gdb --args nix blah blub
- bar
-```
-
-Then, running the test with `./mk/debug-test.sh` will drop you into GDB once the script reaches that point:
-
-```shell-session
-$ ./mk/debug-test.sh tests/${testName}.sh
-...
-+ gdb blash blub
-GNU gdb (GDB) 12.1
-...
-(gdb)
-```
-
-One can debug the Nix invocation in all the usual ways.
-For example, enter `run` to start the Nix invocation.
-
-### Integration tests
-
-The integration tests are defined in the Nix flake under the `hydraJobs.tests` attribute.
-These tests include everything that needs to interact with external services or run Nix in a non-trivial distributed setup.
-Because these tests are expensive and require more than what the standard github-actions setup provides, they only run on the master branch (on <https://hydra.nixos.org/jobset/nix/master>).
-
-You can run them manually with `nix build .#hydraJobs.tests.{testName}` or `nix-build -A hydraJobs.tests.{testName}`
-
-### Installer tests
-
-After a one-time setup, the Nix repository's GitHub Actions continuous integration (CI) workflow can test the installer each time you push to a branch.
-
-Creating a Cachix cache for your installer tests and adding its authorization token to GitHub enables [two installer-specific jobs in the CI workflow](https://github.com/NixOS/nix/blob/88a45d6149c0e304f6eb2efcc2d7a4d0d569f8af/.github/workflows/ci.yml#L50-L91):
-
-- The `installer` job generates installers for the platforms below and uploads them to your Cachix cache:
-  - `x86_64-linux`
-  - `armv6l-linux`
-  - `armv7l-linux`
-  - `x86_64-darwin`
-
-- The `installer_test` job (which runs on `ubuntu-latest` and `macos-latest`) will try to install Nix with the cached installer and run a trivial Nix command.
-
-#### One-time setup
-
-1. Have a GitHub account with a fork of the [Nix repository](https://github.com/NixOS/nix).
-2. At cachix.org:
-    - Create or log in to an account.
-    - Create a Cachix cache using the format `<github-username>-nix-install-tests`.
-    - Navigate to the new cache > Settings > Auth Tokens.
-    - Generate a new Cachix auth token and copy the generated value.
-3. At github.com:
-    - Navigate to your Nix fork > Settings > Secrets > Actions > New repository secret.
-    - Name the secret `CACHIX_AUTH_TOKEN`.
-    - Paste the copied value of the Cachix cache auth token.
-
-#### Using the CI-generated installer for manual testing
-
-After the CI run completes, you can check the output to extract the installer URL:
-1. Click into the detailed view of the CI run.
-2. Click into any `installer_test` run (the URL you're here to extract will be the same in all of them).
-3. Click into the `Run cachix/install-nix-action@v...` step and click the detail triangle next to the first log line (it will also be `Run cachix/install-nix-action@v...`)
-4. Copy the value of `install_url`
-5. To generate an install command, plug this `install_url` and your GitHub username into this template:
-
-    ```console
-    curl -L <install_url> | sh -s -- --tarball-url-prefix https://<github-username>-nix-install-tests.cachix.org/serve
-    ```
-
-<!-- #### Manually generating test installers
-
-There's obviously a manual way to do this, and it's still the only way for
-platforms that lack GA runners.
-
-I did do this back in Fall 2020 (before the GA approach encouraged here). I'll
-sketch what I recall in case it encourages someone to fill in detail, but: I
-didn't know what I was doing at the time and had to fumble/ask around a lot--
-so I don't want to uphold any of it as "right". It may have been dumb or
-the _hard_ way from the getgo. Fundamentals may have changed since.
-
-Here's the build command I used to do this on and for x86_64-darwin:
-nix build --out-link /tmp/foo ".#checks.x86_64-darwin.binaryTarball"
-
-I used the stable out-link to make it easier to script the next steps:
-link=$(readlink /tmp/foo)
-cp $link/*-darwin.tar.xz ~/somewheres
-
-I've lost the last steps and am just going from memory:
-
-From here, I think I had to extract and modify the `install` script to point
-it at this tarball (which I scped to my own site, but it might make more sense
-to just share them locally). I extracted this script once and then just
-search/replaced in it for each new build.
-
-The installer now supports a `--tarball-url-prefix` flag which _may_ have
-solved this need?
--->
-
-### Checking links in the manual
-
-The build checks for broken internal links.
-This happens late in the process, so `nix build` is not suitable for iterating.
-To build the manual incrementally, run:
-
-```console
-make html -j $NIX_BUILD_CORES
-```
-
-In order to reflect changes to the [Makefile], clear all generated files before re-building:
-
-[Makefile]: https://github.com/NixOS/nix/blob/master/doc/manual/local.mk
-
-```console
-rm $(git ls-files doc/manual/ -o | grep -F '.md') && rmdir doc/manual/src/command-ref/new-cli && make html -j $NIX_BUILD_CORES
-```
-
-[`mdbook-linkcheck`] does not implement checking [URI fragments] yet.
-
-[`mdbook-linkcheck`]: https://github.com/Michael-F-Bryan/mdbook-linkcheck
-[URI fragments]: https://en.m.wikipedia.org/wiki/URI_fragment
-
-#### `@docroot@` variable
-
-`@docroot@` provides a base path for links that occur in reusable snippets or other documentation that doesn't have a base path of its own.
-
-If a broken link occurs in a snippet that was inserted into multiple generated files in different directories, use `@docroot@` to reference the `doc/manual/src` directory.
-
-If the `@docroot@` literal appears in an error message from the `mdbook-linkcheck` tool, the `@docroot@` replacement needs to be applied to the generated source file that mentions it.
-See existing `@docroot@` logic in the [Makefile].
-Regular markdown files used for the manual have a base path of their own and they can use relative paths instead of `@docroot@`.
-
-## API documentation
-
-Doxygen API documentation is [available
-online](https://hydra.nixos.org/job/nix/master/internal-api-docs/latest/download-by-type/doc/internal-api-docs). You
-can also build and view it yourself:
-
-```console
-# nix build .#hydraJobs.internal-api-docs
-# xdg-open ./result/share/doc/nix/internal-api/html/index.html
-```
-
-or inside a `nix develop` shell by running:
-
-```
-# make internal-api-html
-# xdg-open ./outputs/doc/share/doc/nix/internal-api/html/index.html
-```
-
-## Coverage analysis
-
-A coverage analysis report is [available
-online](https://hydra.nixos.org/job/nix/master/coverage/latest/download-by-type/report/coverage). You
-can build it yourself:
-
-```
-# nix build .#hydraJobs.coverage
-# xdg-open ./result/coverage/index.html
-```
-
-Metrics about the change in line/function coverage over time are also
-[available](https://hydra.nixos.org/job/nix/master/coverage#tabs-charts).

doc/manual/src/contributing/testing.md

@@ -0,0 +1,304 @@
+# Running tests
+
+## Coverage analysis
+
+A [coverage analysis report] is available online
+You can build it yourself:
+
+[coverage analysis report]: https://hydra.nixos.org/job/nix/master/coverage/latest/download-by-type/report/coverage
+
+```
+# nix build .#hydraJobs.coverage
+# xdg-open ./result/coverage/index.html
+```
+
+[Extensive records of build metrics](https://hydra.nixos.org/job/nix/master/coverage#tabs-charts), such as test coverage over time, are also available online.
+
+## Unit-tests
+
+The unit tests are defined using the [googletest] and [rapidcheck] frameworks.
+
+[googletest]: https://google.github.io/googletest/
+[rapidcheck]: https://github.com/emil-e/rapidcheck
+
+### Source and header layout
+
+> An example of some files, demonstrating much of what is described below
+>
+> ```
+> src
+> ├── libexpr
+> │   ├── value/context.hh
+> │   ├── value/context.cc
+> │   │
+> │   …
+>     └── tests
+> │       ├── value/context.hh
+> │       ├── value/context.cc
+> │       │
+> │       …
+> │
+> ├── unit-test-data
+> │   ├── libstore
+> │   │   ├── worker-protocol/content-address.bin
+> │   │   …
+> │   …
+> …
+> ```
+
+The unit tests for each Nix library (`libnixexpr`, `libnixstore`, etc..) live inside a directory `src/${library_shortname}/tests` within the directory for the library (`src/${library_shortname}`).
+
+The data is in `unit-test-data`, with one subdir per library, with the same name as where the code goes.
+For example, `libnixstore` code is in `src/libstore`, and its test data is in `unit-test-data/libstore`.
+The path to the `unit-test-data` directory is passed to the unit test executable with the environment variable `_NIX_TEST_UNIT_DATA`.
+
+> **Note**
+> Due to the way googletest works, downstream unit test executables will actually include and re-run upstream library tests.
+> Therefore it is important that the same value for `_NIX_TEST_UNIT_DATA` be used with the tests for each library.
+> That is why we have the test data nested within a single `unit-test-data` directory.
+
+### Running tests
+
+You can run the whole testsuite with `make check`, or the tests for a specific component with `make libfoo-tests_RUN`.
+Finer-grained filtering is also possible using the [--gtest_filter](https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests) command-line option, or the `GTEST_FILTER` environment variable.
+
+### Characterisation testing { #characaterisation-testing-unit }
+
+See [functional characterisation testing](#characterisation-testing-functional) for a broader discussion of characterisation testing.
+
+Like with the functional characterisation, `_NIX_TEST_ACCEPT=1` is also used.
+For example:
+```shell-session
+$ _NIX_TEST_ACCEPT=1 make libstore-tests-exe_RUN
+...
+[  SKIPPED ] WorkerProtoTest.string_read
+[  SKIPPED ] WorkerProtoTest.string_write
+[  SKIPPED ] WorkerProtoTest.storePath_read
+[  SKIPPED ] WorkerProtoTest.storePath_write
+...
+```
+will regenerate the "golden master" expected result for the `libnixstore` characterisation tests.
+The characterisation tests will mark themselves "skipped" since they regenerated the expected result instead of actually testing anything.
+
+## Functional tests
+
+The functional tests reside under the `tests/functional` directory and are listed in `tests/functional/local.mk`.
+Each test is a bash script.
+
+### Running the whole test suite
+
+The whole test suite can be run with:
+
+```shell-session
+$ make install && make installcheck
+ran test tests/functional/foo.sh... [PASS]
+ran test tests/functional/bar.sh... [PASS]
+...
+```
+
+### Grouping tests
+
+Sometimes it is useful to group related tests so they can be easily run together without running the entire test suite.
+Each test group is in a subdirectory of `tests`.
+For example, `tests/functional/ca/local.mk` defines a `ca` test group for content-addressed derivation outputs.
+
+That test group can be run like this:
+
+```shell-session
+$ make ca.test-group -j50
+ran test tests/functional/ca/nix-run.sh... [PASS]
+ran test tests/functional/ca/import-derivation.sh... [PASS]
+...
+```
+
+The test group is defined in Make like this:
+```makefile
+$(test-group-name)-tests := \
+  $(d)/test0.sh \
+  $(d)/test1.sh \
+  ...
+
+install-tests-groups += $(test-group-name)
+```
+
+### Running individual tests
+
+Individual tests can be run with `make`:
+
+```shell-session
+$ make tests/functional/${testName}.sh.test
+ran test tests/functional/${testName}.sh... [PASS]
+```
+
+or without `make`:
+
+```shell-session
+$ ./mk/run-test.sh tests/functional/${testName}.sh tests/functional/init.sh
+ran test tests/functional/${testName}.sh... [PASS]
+```
+
+To see the complete output, one can also run:
+
+```shell-session
+$ ./mk/debug-test.sh tests/functional/${testName}.sh tests/functional/init.sh
++(${testName}.sh:1) foo
+output from foo
++(${testName}.sh:2) bar
+output from bar
+...
+```
+
+The test script will then be traced with `set -x` and the output displayed as it happens, regardless of whether the test succeeds or fails.
+
+### Debugging failing functional tests
+
+When a functional test fails, it usually does so somewhere in the middle of the script.
+
+To figure out what's wrong, it is convenient to run the test regularly up to the failing `nix` command, and then run that command with a debugger like GDB.
+
+For example, if the script looks like:
+
+```bash
+foo
+nix blah blub
+bar
+```
+edit it like so:
+
+```diff
+ foo
+-nix blah blub
++gdb --args nix blah blub
+ bar
+```
+
+Then, running the test with `./mk/debug-test.sh` will drop you into GDB once the script reaches that point:
+
+```shell-session
+$ ./mk/debug-test.sh tests/functional/${testName}.sh tests/functional/init.sh
+...
++ gdb blash blub
+GNU gdb (GDB) 12.1
+...
+(gdb)
+```
+
+One can debug the Nix invocation in all the usual ways.
+For example, enter `run` to start the Nix invocation.
+
+### Troubleshooting
+
+Sometimes running tests in the development shell may leave artefacts in the local repository.
+To remove any traces of that:
+
+```console
+git clean -x --force tests
+```
+
+### Characterisation testing { #characterisation-testing-functional }
+
+Occasionally, Nix utilizes a technique called [Characterisation Testing](https://en.wikipedia.org/wiki/Characterization_test) as part of the functional tests.
+This technique is to include the exact output/behavior of a former version of Nix in a test in order to check that Nix continues to produce the same behavior going forward.
+
+For example, this technique is used for the language tests, to check both the printed final value if evaluation was successful, and any errors and warnings encountered.
+
+It is frequently useful to regenerate the expected output.
+To do that, rerun the failed test(s) with `_NIX_TEST_ACCEPT=1`.
+For example:
+```bash
+_NIX_TEST_ACCEPT=1 make tests/functional/lang.sh.test
+```
+This convention is shared with the [characterisation unit tests](#characterisation-testing-unit) too.
+
+An interesting situation to document is the case when these tests are "overfitted".
+The language tests are, again, an example of this.
+The expected successful output of evaluation is supposed to be highly stable – we do not intend to make breaking changes to (the stable parts of) the Nix language.
+However, the errors and warnings during evaluation (successful or not) are not stable in this way.
+We are free to change how they are displayed at any time.
+
+It may be surprising that we would test non-normative behavior like diagnostic outputs.
+Diagnostic outputs are indeed not a stable interface, but they still are important to users.
+By recording the expected output, the test suite guards against accidental changes, and ensure the *result* (not just the code that implements it) of the diagnostic code paths are under code review.
+Regressions are caught, and improvements always show up in code review.
+
+To ensure that characterisation testing doesn't make it harder to intentionally change these interfaces, there always must be an easy way to regenerate the expected output, as we do with `_NIX_TEST_ACCEPT=1`.
+
+## Integration tests
+
+The integration tests are defined in the Nix flake under the `hydraJobs.tests` attribute.
+These tests include everything that needs to interact with external services or run Nix in a non-trivial distributed setup.
+Because these tests are expensive and require more than what the standard github-actions setup provides, they only run on the master branch (on <https://hydra.nixos.org/jobset/nix/master>).
+
+You can run them manually with `nix build .#hydraJobs.tests.{testName}` or `nix-build -A hydraJobs.tests.{testName}`
+
+## Installer tests
+
+After a one-time setup, the Nix repository's GitHub Actions continuous integration (CI) workflow can test the installer each time you push to a branch.
+
+Creating a Cachix cache for your installer tests and adding its authorisation token to GitHub enables [two installer-specific jobs in the CI workflow](https://github.com/NixOS/nix/blob/88a45d6149c0e304f6eb2efcc2d7a4d0d569f8af/.github/workflows/ci.yml#L50-L91):
+
+- The `installer` job generates installers for the platforms below and uploads them to your Cachix cache:
+  - `x86_64-linux`
+  - `armv6l-linux`
+  - `armv7l-linux`
+  - `x86_64-darwin`
+
+- The `installer_test` job (which runs on `ubuntu-latest` and `macos-latest`) will try to install Nix with the cached installer and run a trivial Nix command.
+
+### One-time setup
+
+1. Have a GitHub account with a fork of the [Nix repository](https://github.com/NixOS/nix).
+2. At cachix.org:
+    - Create or log in to an account.
+    - Create a Cachix cache using the format `<github-username>-nix-install-tests`.
+    - Navigate to the new cache > Settings > Auth Tokens.
+    - Generate a new Cachix auth token and copy the generated value.
+3. At github.com:
+    - Navigate to your Nix fork > Settings > Secrets > Actions > New repository secret.
+    - Name the secret `CACHIX_AUTH_TOKEN`.
+    - Paste the copied value of the Cachix cache auth token.
+
+## Working on documentation
+
+### Using the CI-generated installer for manual testing
+
+After the CI run completes, you can check the output to extract the installer URL:
+1. Click into the detailed view of the CI run.
+2. Click into any `installer_test` run (the URL you're here to extract will be the same in all of them).
+3. Click into the `Run cachix/install-nix-action@v...` step and click the detail triangle next to the first log line (it will also be `Run cachix/install-nix-action@v...`)
+4. Copy the value of `install_url`
+5. To generate an install command, plug this `install_url` and your GitHub username into this template:
+
+    ```console
+    curl -L <install_url> | sh -s -- --tarball-url-prefix https://<github-username>-nix-install-tests.cachix.org/serve
+    ```
+
+<!-- #### Manually generating test installers
+
+There's obviously a manual way to do this, and it's still the only way for
+platforms that lack GA runners.
+
+I did do this back in Fall 2020 (before the GA approach encouraged here). I'll
+sketch what I recall in case it encourages someone to fill in detail, but: I
+didn't know what I was doing at the time and had to fumble/ask around a lot--
+so I don't want to uphold any of it as "right". It may have been dumb or
+the _hard_ way from the getgo. Fundamentals may have changed since.
+
+Here's the build command I used to do this on and for x86_64-darwin:
+nix build --out-link /tmp/foo ".#checks.x86_64-darwin.binaryTarball"
+
+I used the stable out-link to make it easier to script the next steps:
+link=$(readlink /tmp/foo)
+cp $link/*-darwin.tar.xz ~/somewheres
+
+I've lost the last steps and am just going from memory:
+
+From here, I think I had to extract and modify the `install` script to point
+it at this tarball (which I scped to my own site, but it might make more sense
+to just share them locally). I extracted this script once and then just
+search/replaced in it for each new build.
+
+The installer now supports a `--tarball-url-prefix` flag which _may_ have
+solved this need?
+-->
+

doc/manual/src/glossary.md

@@ -1,230 +1,284 @@
 # Glossary
 
-  - [derivation]{#gloss-derivation}\
-    A description of a build task. The result of a derivation is a
-    store object. Derivations are typically specified in Nix expressions
-    using the [`derivation` primitive](./language/derivations.md). These are
-    translated into low-level *store derivations* (implicitly by
-    `nix-env` and `nix-build`, or explicitly by `nix-instantiate`).
+- [derivation]{#gloss-derivation}
 
-    [derivation]: #gloss-derivation
+  A description of a build task. The result of a derivation is a
+  store object. Derivations are typically specified in Nix expressions
+  using the [`derivation` primitive](./language/derivations.md). These are
+  translated into low-level *store derivations* (implicitly by
+  `nix-env` and `nix-build`, or explicitly by `nix-instantiate`).
 
-  - [store derivation]{#gloss-store-derivation}\
-    A [derivation] represented as a `.drv` file in the [store].
-    It has a [store path], like any [store object].
+  [derivation]: #gloss-derivation
 
-    Example: `/nix/store/g946hcz4c8mdvq2g8vxx42z51qb71rvp-git-2.38.1.drv`
+- [store derivation]{#gloss-store-derivation}
 
-    See [`nix derivation show`](./command-ref/new-cli/nix3-derivation-show.md) (experimental) for displaying the contents of store derivations.
+  A [derivation] represented as a `.drv` file in the [store].
+  It has a [store path], like any [store object].
 
-    [store derivation]: #gloss-store-derivation
+  Example: `/nix/store/g946hcz4c8mdvq2g8vxx42z51qb71rvp-git-2.38.1.drv`
 
-  - [instantiate]{#gloss-instantiate}, instantiation\
-    Translate a [derivation] into a [store derivation].
+  See [`nix derivation show`](./command-ref/new-cli/nix3-derivation-show.md) (experimental) for displaying the contents of store derivations.
 
-    See [`nix-instantiate`](./command-ref/nix-instantiate.md).
+  [store derivation]: #gloss-store-derivation
 
-    [instantiate]: #gloss-instantiate
+- [instantiate]{#gloss-instantiate}, instantiation
 
-  - [realise]{#gloss-realise}, realisation\
-    Ensure a [store path] is [valid][validity].
+  Translate a [derivation] into a [store derivation].
 
-    This means either running the `builder` executable as specified in the corresponding [derivation] or fetching a pre-built [store object] from a [substituter].
+  See [`nix-instantiate`](./command-ref/nix-instantiate.md).
 
-    See [`nix-build`](./command-ref/nix-build.md) and [`nix-store --realise`](@docroot@/command-ref/nix-store/realise.md).
+  [instantiate]: #gloss-instantiate
 
-    See [`nix build`](./command-ref/new-cli/nix3-build.md) (experimental).
+- [realise]{#gloss-realise}, realisation
 
-    [realise]: #gloss-realise
+  Ensure a [store path] is [valid][validity].
 
-  - [content-addressed derivation]{#gloss-content-addressed-derivation}\
-    A derivation which has the
-    [`__contentAddressed`](./language/advanced-attributes.md#adv-attr-__contentAddressed)
-    attribute set to `true`.
+  This can be achieved by:
+  - Fetching a pre-built [store object] from a [substituter]
+  - Running the [`builder`](@docroot@/language/derivations.md#attr-builder) executable as specified in the corresponding [derivation]
+  - Delegating to a [remote builder](@docroot@/advanced-topics/distributed-builds.html) and retrieving the outputs
+  <!-- TODO: link [running] to build process page, #8888 -->
 
-  - [fixed-output derivation]{#gloss-fixed-output-derivation}\
-    A derivation which includes the
-    [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute.
+  See [`nix-store --realise`](@docroot@/command-ref/nix-store/realise.md) for a detailed description of the algorithm.
 
-  - [store]{#gloss-store}\
-    The location in the file system where store objects live. Typically
-    `/nix/store`.
+  See also [`nix-build`](./command-ref/nix-build.md) and [`nix build`](./command-ref/new-cli/nix3-build.md) (experimental).
 
-    From   the  perspective   of   the  location   where  Nix   is
-    invoked, the  Nix store can be  referred to
-    as a "_local_" or a "_remote_" one:
+  [realise]: #gloss-realise
 
-    + A [local store]{#gloss-local-store} exists on the filesystem of
-      the machine where Nix is  invoked. You can use other
-      local stores  by passing  the `--store` flag  to the
-      `nix` command.  Local stores can be used for building derivations.
+- [content-addressed derivation]{#gloss-content-addressed-derivation}
 
-    + A  *remote store*  exists  anywhere  other than  the
-      local  filesystem. One  example is  the `/nix/store`
-      directory on another machine,  accessed via `ssh` or
-      served by the `nix-serve` Perl script.
+  A derivation which has the
+  [`__contentAddressed`](./language/advanced-attributes.md#adv-attr-__contentAddressed)
+  attribute set to `true`.
 
-    [store]: #gloss-store
-    [local store]: #gloss-local-store
+- [fixed-output derivation]{#gloss-fixed-output-derivation}
 
-  - [chroot store]{#gloss-chroot-store}\
-    A [local store] whose canonical path is anything other than `/nix/store`.
+  A derivation which includes the
+  [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute.
 
-  - [binary cache]{#gloss-binary-cache}\
-    A *binary cache* is a Nix store which uses a different format: its
-    metadata and signatures are kept in `.narinfo` files rather than in a
-    [Nix database]. This different format simplifies serving store objects
-    over the network, but cannot host builds. Examples of binary caches
-    include S3 buckets and the [NixOS binary cache](https://cache.nixos.org).
+- [store]{#gloss-store}
 
-  - [store path]{#gloss-store-path}\
-    The location of a [store object] in the file system, i.e., an
-    immediate child of the Nix store directory.
+  A collection of store objects, with operations to manipulate that collection.
+  See [Nix store](./store/index.md) for details.
 
-    Example: `/nix/store/a040m110amc4h71lds2jmr8qrkj2jhxd-git-2.38.1`
+  There are many types of stores.
+  See [`nix help-stores`](@docroot@/command-ref/new-cli/nix3-help-stores.md) for a complete list.
 
-    [store path]: #gloss-store-path
+  From the perspective of the location where Nix is invoked, the Nix store can be  referred to _local_ or _remote_.
+  Only a [local store]{#gloss-local-store} exposes a location in the file system of the machine where Nix is invoked that allows access to store objects, typically `/nix/store`.
+  Local stores can be used for building [derivations](#derivation).
+  See [Local Store](@docroot@/command-ref/new-cli/nix3-help-stores.md#local-store) for details.
 
-  - [store object]{#gloss-store-object}\
-    A file that is an immediate child of the Nix store directory. These
-    can be regular files, but also entire directory trees. Store objects
-    can be sources (objects copied from outside of the store),
-    derivation outputs (objects produced by running a build task), or
-    derivations (files describing a build task).
+  [store]: #gloss-store
+  [local store]: #gloss-local-store
 
-    [store object]: #gloss-store-object
+- [chroot store]{#gloss-chroot-store}
 
-  - [input-addressed store object]{#gloss-input-addressed-store-object}\
-    A store object produced by building a
-    non-[content-addressed](#gloss-content-addressed-derivation),
-    non-[fixed-output](#gloss-fixed-output-derivation)
-    derivation.
+  A [local store] whose canonical path is anything other than `/nix/store`.
 
-  - [output-addressed store object]{#gloss-output-addressed-store-object}\
-    A [store object] whose [store path] is determined by its contents.
-    This includes derivations, the outputs of [content-addressed derivations](#gloss-content-addressed-derivation), and the outputs of [fixed-output derivations](#gloss-fixed-output-derivation).
+- [binary cache]{#gloss-binary-cache}
 
-  - [substitute]{#gloss-substitute}\
-    A substitute is a command invocation stored in the [Nix database] that
-    describes how to build a store object, bypassing the normal build
-    mechanism (i.e., derivations). Typically, the substitute builds the
-    store object by downloading a pre-built version of the store object
-    from some server.
+  A *binary cache* is a Nix store which uses a different format: its
+  metadata and signatures are kept in `.narinfo` files rather than in a
+  [Nix database]. This different format simplifies serving store objects
+  over the network, but cannot host builds. Examples of binary caches
+  include S3 buckets and the [NixOS binary cache](https://cache.nixos.org).
 
-  - [substituter]{#gloss-substituter}\
-    A *substituter* is an additional store from which Nix will
-    copy store objects it doesn't have.  For details, see the
-    [`substituters` option](./command-ref/conf-file.md#conf-substituters).
+- [store path]{#gloss-store-path}
 
-    [substituter]: #gloss-substituter
+  The location of a [store object](@docroot@/store/index.md#store-object) in the file system, i.e., an immediate child of the Nix store directory.
 
-  - [purity]{#gloss-purity}\
-    The assumption that equal Nix derivations when run always produce
-    the same output. This cannot be guaranteed in general (e.g., a
-    builder can rely on external inputs such as the network or the
-    system time) but the Nix model assumes it.
+  > **Example**
+  >
+  > `/nix/store/a040m110amc4h71lds2jmr8qrkj2jhxd-git-2.38.1`
 
-  - [Nix database]{#gloss-nix-database}\
-    An SQlite database to track [reference]s between [store object]s.
-    This is an implementation detail of the [local store].
+  See [Store Path](@docroot@/store/store-path.md) for details.
 
-    Default location: `/nix/var/nix/db`.
+  [store path]: #gloss-store-path
 
-    [Nix database]: #gloss-nix-database
+- [file system object]{#gloss-store-object}
 
-  - [Nix expression]{#gloss-nix-expression}\
-    A high-level description of software packages and compositions
-    thereof. Deploying software using Nix entails writing Nix
-    expressions for your packages. Nix expressions are translated to
-    derivations that are stored in the Nix store. These derivations can
-    then be built.
+  The Nix data model for representing simplified file system data.
 
-  - [reference]{#gloss-reference}\
-    A [store object] `O` is said to have a *reference* to a store object `P` if a [store path] to `P` appears in the contents of `O`.
+  See [File System Object](@docroot@/store/file-system-object.md) for details.
 
-    Store objects can refer to both other store objects and themselves.
-    References from a store object to itself are called *self-references*.
-    References other than a self-reference must not form a cycle.
+  [file system object]: #gloss-file-system-object
 
-    [reference]: #gloss-reference
+- [store object]{#gloss-store-object}
 
-  - [reachable]{#gloss-reachable}\
-    A store path `Q` is reachable from another store path `P` if `Q`
-    is in the *closure* of the *references* relation.
+  Part of the contents of a [store].
 
-  - [closure]{#gloss-closure}\
-    The closure of a store path is the set of store paths that are
-    directly or indirectly “reachable” from that store path; that is,
-    it’s the closure of the path under the *references* relation. For
-    a package, the closure of its derivation is equivalent to the
-    build-time dependencies, while the closure of its output path is
-    equivalent to its runtime dependencies. For correct deployment it
-    is necessary to deploy whole closures, since otherwise at runtime
-    files could be missing. The command `nix-store --query --requisites ` prints out
-    closures of store paths.
+  A store object consists of a [file system object], [references][reference] to other store objects, and other metadata.
+  It can be referred to by a [store path].
 
-    As an example, if the [store object] at path `P` contains a [reference]
-    to a store object at path `Q`, then `Q` is in the closure of `P`. Further, if `Q`
-    references `R` then `R` is also in the closure of `P`.
+  See [Store Object](@docroot@/store/index.md#store-object) for details.
 
-    [closure]: #gloss-closure
+  [store object]: #gloss-store-object
 
-  - [output path]{#gloss-output-path}\
-    A [store path] produced by a [derivation].
+- [IFD]{#gloss-ifd}
 
-    [output path]: #gloss-output-path
+  [Import From Derivation](./language/import-from-derivation.md)
 
-  - [deriver]{#gloss-deriver}\
-    The [store derivation] that produced an [output path].
+- [input-addressed store object]{#gloss-input-addressed-store-object}
 
-  - [validity]{#gloss-validity}\
-    A store path is valid if all [store object]s in its [closure] can be read from the [store].
+  A store object produced by building a
+  non-[content-addressed](#gloss-content-addressed-derivation),
+  non-[fixed-output](#gloss-fixed-output-derivation)
+  derivation.
 
-    For a [local store], this means:
-    - The store path leads to an existing [store object] in that [store].
-    - The store path is listed in the [Nix database] as being valid.
-    - All paths in the store path's [closure] are valid.
+- [output-addressed store object]{#gloss-output-addressed-store-object}
 
-    [validity]: #gloss-validity
+  A [store object] whose [store path] is determined by its contents.
+  This includes derivations, the outputs of [content-addressed derivations](#gloss-content-addressed-derivation), and the outputs of [fixed-output derivations](#gloss-fixed-output-derivation).
 
-  - [user environment]{#gloss-user-env}\
-    An automatically generated store object that consists of a set of
-    symlinks to “active” applications, i.e., other store paths. These
-    are generated automatically by
-    [`nix-env`](./command-ref/nix-env.md). See *profiles*.
+- [substitute]{#gloss-substitute}
 
-  - [profile]{#gloss-profile}\
-    A symlink to the current *user environment* of a user, e.g.,
-    `/nix/var/nix/profiles/default`.
+  A substitute is a command invocation stored in the [Nix database] that
+  describes how to build a store object, bypassing the normal build
+  mechanism (i.e., derivations). Typically, the substitute builds the
+  store object by downloading a pre-built version of the store object
+  from some server.
 
-  - [installable]{#gloss-installable}\
-    Something that can be realised in the Nix store.
+- [substituter]{#gloss-substituter}
 
-    See [installables](./command-ref/new-cli/nix.md#installables) for [`nix` commands](./command-ref/new-cli/nix.md) (experimental) for details.
+  An additional [store]{#gloss-store} from which Nix can obtain store objects instead of building them.
+  Often the substituter is a [binary cache](#gloss-binary-cache), but any store can serve as substituter.
 
-  - [NAR]{#gloss-nar}\
-    A *N*ix *AR*chive. This is a serialisation of a path in the Nix
-    store. It can contain regular files, directories and symbolic
-    links.  NARs are generated and unpacked using `nix-store --dump`
-    and `nix-store --restore`.
+  See the [`substituters` configuration option](./command-ref/conf-file.md#conf-substituters) for details.
 
-  - [`∅`]{#gloss-emtpy-set}\
-    The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile.
+  [substituter]: #gloss-substituter
 
-  - [`ε`]{#gloss-epsilon}\
-    The epsilon symbol. In the context of a package, this means the version is empty. More precisely, the derivation does not have a version attribute.
+- [purity]{#gloss-purity}
 
-  - [string interpolation]{#gloss-string-interpolation}\
-    Expanding expressions enclosed in `${ }` within a [string], [path], or [attribute name].
+  The assumption that equal Nix derivations when run always produce
+  the same output. This cannot be guaranteed in general (e.g., a
+  builder can rely on external inputs such as the network or the
+  system time) but the Nix model assumes it.
 
-    See [String interpolation](./language/string-interpolation.md) for details.
+- [Nix database]{#gloss-nix-database}
 
-    [string]: ./language/values.md#type-string
-    [path]: ./language/values.md#type-path
-    [attribute name]: ./language/values.md#attribute-set
+  An SQlite database to track [reference]s between [store object]s.
+  This is an implementation detail of the [local store].
 
-  - [experimental feature]{#gloss-experimental-feature}\
-    Not yet stabilized functionality guarded by named experimental feature flags.
-    These flags are enabled or disabled with the [`experimental-features`](./command-ref/conf-file.html#conf-experimental-features) setting.
+  Default location: `/nix/var/nix/db`.
 
-    See the contribution guide on the [purpose and lifecycle of experimental feaures](@docroot@/contributing/experimental-features.md).
+  [Nix database]: #gloss-nix-database
+
+- [Nix expression]{#gloss-nix-expression}
+
+  A high-level description of software packages and compositions
+  thereof. Deploying software using Nix entails writing Nix
+  expressions for your packages. Nix expressions are translated to
+  derivations that are stored in the Nix store. These derivations can
+  then be built.
+
+- [reference]{#gloss-reference}
+
+  A [store object] `O` is said to have a *reference* to a store object `P` if a [store path] to `P` appears in the contents of `O`.
+
+  Store objects can refer to both other store objects and themselves.
+  References from a store object to itself are called *self-references*.
+  References other than a self-reference must not form a cycle.
+
+  [reference]: #gloss-reference
+
+- [reachable]{#gloss-reachable}
+
+  A store path `Q` is reachable from another store path `P` if `Q`
+  is in the *closure* of the *references* relation.
+
+- [closure]{#gloss-closure}
+
+  The closure of a store path is the set of store paths that are
+  directly or indirectly “reachable” from that store path; that is,
+  it’s the closure of the path under the *references* relation. For
+  a package, the closure of its derivation is equivalent to the
+  build-time dependencies, while the closure of its output path is
+  equivalent to its runtime dependencies. For correct deployment it
+  is necessary to deploy whole closures, since otherwise at runtime
+  files could be missing. The command `nix-store --query --requisites ` prints out
+  closures of store paths.
+
+  As an example, if the [store object] at path `P` contains a [reference]
+  to a store object at path `Q`, then `Q` is in the closure of `P`. Further, if `Q`
+  references `R` then `R` is also in the closure of `P`.
+
+  [closure]: #gloss-closure
+
+- [output]{#gloss-output}
+
+  A [store object] produced by a [derivation].
+  See [the `outputs` argument to the `derivation` function](@docroot@/language/derivations.md#attr-outputs) for details.
+
+  [output]: #gloss-output
+
+- [output path]{#gloss-output-path}
+
+  The [store path] to the [output] of a [derivation].
+
+  [output path]: #gloss-output-path
+
+- [deriver]{#gloss-deriver}
+
+  The [store derivation] that produced an [output path].
+
+- [validity]{#gloss-validity}
+
+  A store path is valid if all [store object]s in its [closure] can be read from the [store].
+
+  For a [local store], this means:
+  - The store path leads to an existing [store object] in that [store].
+  - The store path is listed in the [Nix database] as being valid.
+  - All paths in the store path's [closure] are valid.
+
+  [validity]: #gloss-validity
+
+- [user environment]{#gloss-user-env}
+
+  An automatically generated store object that consists of a set of
+  symlinks to “active” applications, i.e., other store paths. These
+  are generated automatically by
+  [`nix-env`](./command-ref/nix-env.md). See *profiles*.
+
+- [profile]{#gloss-profile}
+
+  A symlink to the current *user environment* of a user, e.g.,
+  `/nix/var/nix/profiles/default`.
+
+- [installable]{#gloss-installable}
+
+  Something that can be realised in the Nix store.
+
+  See [installables](./command-ref/new-cli/nix.md#installables) for [`nix` commands](./command-ref/new-cli/nix.md) (experimental) for details.
+
+- [NAR]{#gloss-nar}
+
+  A *N*ix *AR*chive. This is a serialisation of a path in the Nix
+  store. It can contain regular files, directories and symbolic
+  links.  NARs are generated and unpacked using `nix-store --dump`
+  and `nix-store --restore`.
+
+- [`∅`]{#gloss-emtpy-set}
+
+  The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile.
+
+- [`ε`]{#gloss-epsilon}
+
+  The epsilon symbol. In the context of a package, this means the version is empty. More precisely, the derivation does not have a version attribute.
+
+- [string interpolation]{#gloss-string-interpolation}
+
+  Expanding expressions enclosed in `${ }` within a [string], [path], or [attribute name].
+
+  See [String interpolation](./language/string-interpolation.md) for details.
+
+  [string]: ./language/values.md#type-string
+  [path]: ./language/values.md#type-path
+  [attribute name]: ./language/values.md#attribute-set
+
+- [experimental feature]{#gloss-experimental-feature}
+
+  Not yet stabilized functionality guarded by named experimental feature flags.
+  These flags are enabled or disabled with the [`experimental-features`](./command-ref/conf-file.html#conf-experimental-features) setting.
+
+  See the contribution guide on the [purpose and lifecycle of experimental feaures](@docroot@/contributing/experimental-features.md).

doc/manual/src/installation/building-source.md

@@ -3,7 +3,7 @@
 After cloning Nix's Git repository, issue the following commands:
 
 ```console
-$ ./bootstrap.sh
+$ autoreconf -vfi
 $ ./configure options...
 $ make
 $ make install

doc/manual/src/installation/installing-docker.md

@@ -3,14 +3,14 @@
 To run the latest stable release of Nix with Docker run the following command:
 
 ```console
-$ docker run -ti nixos/nix
-Unable to find image 'nixos/nix:latest' locally
-latest: Pulling from nixos/nix
+$ docker run -ti ghcr.io/nixos/nix
+Unable to find image 'ghcr.io/nixos/nix:latest' locally
+latest: Pulling from ghcr.io/nixos/nix
 5843afab3874: Pull complete
 b52bf13f109c: Pull complete
 1e2415612aa3: Pull complete
 Digest: sha256:27f6e7f60227e959ee7ece361f75d4844a40e1cc6878b6868fe30140420031ff
-Status: Downloaded newer image for nixos/nix:latest
+Status: Downloaded newer image for ghcr.io/nixos/nix:latest
 35ca4ada6e96:/# nix --version
 nix (Nix) 2.3.12
 35ca4ada6e96:/# exit

doc/manual/src/installation/prerequisites-source.md

@@ -10,7 +10,7 @@
   - Bash Shell. The `./configure` script relies on bashisms, so Bash is
     required.
 
-  - A version of GCC or Clang that supports C++17.
+  - A version of GCC or Clang that supports C++20.
 
   - `pkg-config` to locate dependencies. If your distribution does not
     provide it, you can get it from

doc/manual/src/language/advanced-attributes.md

@@ -112,6 +112,13 @@ Derivations can declare some infrequently used optional attributes.
     > environmental variables come from the environment of the
     > `nix-build`.
 
+    If the [`configurable-impure-env` experimental
+    feature](@docroot@/contributing/experimental-features.md#xp-feature-configurable-impure-env)
+    is enabled, these environment variables can also be controlled
+    through the
+    [`impure-env`](@docroot@/command-ref/conf-file.md#conf-impure-env)
+    configuration setting.
+
   - [`outputHash`]{#adv-attr-outputHash}; [`outputHashAlgo`]{#adv-attr-outputHashAlgo}; [`outputHashMode`]{#adv-attr-outputHashMode}\
     These attributes declare that the derivation is a so-called
     *fixed-output derivation*, which means that a cryptographic hash of
@@ -229,6 +236,8 @@ Derivations can declare some infrequently used optional attributes.
     [`outputHashAlgo`](#adv-attr-outputHashAlgo)
     like for *fixed-output derivations* (see above).
 
+    It also implicitly requires that the machine to build the derivation must have the `ca-derivations` [system feature](@docroot@/command-ref/conf-file.md#conf-system-features).
+
   - [`passAsFile`]{#adv-attr-passAsFile}\
     A list of names of attributes that should be passed via files rather
     than environment variables. For example, if you have
@@ -261,6 +270,9 @@ Derivations can declare some infrequently used optional attributes.
     useful for very trivial derivations (such as `writeText` in Nixpkgs)
     that are cheaper to build than to substitute from a binary cache.
 
+    You may disable the effects of this attibute by enabling the
+    `always-allow-substitutes` configuration option in Nix.
+
     > **Note**
     >
     > You need to have a builder configured which satisfies the
@@ -271,18 +283,21 @@ Derivations can declare some infrequently used optional attributes.
 
   - [`__structuredAttrs`]{#adv-attr-structuredAttrs}\
     If the special attribute `__structuredAttrs` is set to `true`, the other derivation
-    attributes are serialised in JSON format and made available to the
-    builder via the file `.attrs.json` in the builder’s temporary
-    directory. This obviates the need for [`passAsFile`](#adv-attr-passAsFile) since JSON files
-    have no size restrictions, unlike process environments.
+    attributes are serialised into a file in JSON format. The environment variable
+    `NIX_ATTRS_JSON_FILE` points to the exact location of that file both in a build
+    and a [`nix-shell`](../command-ref/nix-shell.md). This obviates the need for
+    [`passAsFile`](#adv-attr-passAsFile) since JSON files have no size restrictions,
+    unlike process environments.
 
     It also makes it possible to tweak derivation settings in a structured way; see
     [`outputChecks`](#adv-attr-outputChecks) for example.
 
     As a convenience to Bash builders,
-    Nix writes a script named `.attrs.sh` to the builder’s directory
-    that initialises shell variables corresponding to all attributes
-    that are representable in Bash. This includes non-nested
+    Nix writes a script that initialises shell variables
+    corresponding to all attributes that are representable in Bash. The
+    environment variable `NIX_ATTRS_SH_FILE` points to the exact
+    location of the script, both in a build and a
+    [`nix-shell`](../command-ref/nix-shell.md). This includes non-nested
     (associative) arrays. For example, the attribute `hardening.format = true`
     ends up as the Bash associative array element `${hardening[format]}`.
 
@@ -320,16 +335,6 @@ Derivations can declare some infrequently used optional attributes.
     ```
 
   - [`unsafeDiscardReferences`]{#adv-attr-unsafeDiscardReferences}\
-    > **Warning**
-    > This attribute is part of an [experimental feature](@docroot@/contributing/experimental-features.md).
-    >
-    > To use this attribute, you must enable the
-    > [`discard-references`](@docroot@/contributing/experimental-features.md#xp-feature-discard-references) experimental feature.
-    > For example, in [nix.conf](../command-ref/conf-file.md) you could add:
-    >
-    > ```
-    > extra-experimental-features = discard-references
-    > ```
 
     When using [structured attributes](#adv-attr-structuredAttrs), the
     attribute `unsafeDiscardReferences` is an attribute set with a boolean value for each output name.
@@ -345,3 +350,15 @@ Derivations can declare some infrequently used optional attributes.
     This is useful, for example, when generating self-contained filesystem images with
     their own embedded Nix store: hashes found inside such an image refer
     to the embedded store and not to the host's Nix store.
+
+- [`requiredSystemFeatures`]{#adv-attr-requiredSystemFeatures}\
+
+  If a derivation has the `requiredSystemFeatures` attribute, then Nix will only build it on a machine that has the corresponding features set in its [`system-features` configuration](@docroot@/command-ref/conf-file.md#conf-system-features).
+
+  For example, setting
+
+  ```nix
+  requiredSystemFeatures = [ "kvm" ];
+  ```
+
+  ensures that the derivation can only be built on a machine with the `kvm` feature.

doc/manual/src/language/builtin-constants-prefix.md

@@ -0,0 +1,5 @@
+# Built-in Constants
+
+These constants are built into the Nix language evaluator:
+
+<dl>

doc/manual/src/language/builtin-constants-suffix.md

@@ -0,0 +1 @@
+</dl>

doc/manual/src/language/builtin-constants.md

@@ -1,43 +0,0 @@
-# Built-in Constants
-
-These constants are built into the Nix language evaluator:
-
-- [`builtins`]{#builtins-builtins} (attribute set)
-
-  Contains all the [built-in functions](./builtins.md) and values, in order to avoid polluting the global scope.
-
-  Since built-in functions were added over time, [testing for attributes](./operators.md#has-attribute) in `builtins` can be used for graceful fallback on older Nix installations:
-
-  ```nix
-  if builtins ? getEnv then builtins.getEnv "PATH" else ""
-  ```
-
-- [`builtins.currentSystem`]{#builtins-currentSystem} (string)
-
-  The built-in value `currentSystem` evaluates to the Nix platform
-  identifier for the Nix installation on which the expression is being
-  evaluated, such as `"i686-linux"` or `"x86_64-darwin"`.
-
-  Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).
-
-- [`builtins.currentTime`]{#builtins-currentTime} (integer)
-
-  Return the [Unix time](https://en.wikipedia.org/wiki/Unix_time) at first evaluation.
-  Repeated references to that name will re-use the initially obtained value.
-
-  Example:
-
-  ```console
-  $ nix repl
-  Welcome to Nix 2.15.1 Type :? for help.
-
-  nix-repl> builtins.currentTime
-  1683705525
-
-  nix-repl> builtins.currentTime
-  1683705525
-  ```
-
-  The [store path](@docroot@/glossary.md#gloss-store-path) of a derivation depending on `currentTime` will differ for each evaluation.
-
-  Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).

doc/manual/src/language/builtins-prefix.md

@@ -3,7 +3,7 @@
 This section lists the functions built into the Nix language evaluator.
 All built-in functions are available through the global [`builtins`](./builtin-constants.md#builtins-builtins) constant.
 
-For convenience, some built-ins are can be accessed directly:
+For convenience, some built-ins can be accessed directly:
 
 - [`derivation`](#builtins-derivation)
 - [`import`](#builtins-import)

doc/manual/src/language/constructs.md

@@ -2,8 +2,11 @@
 
 ## Recursive sets
 
-Recursive sets are just normal sets, but the attributes can refer to
-each other. For example,
+Recursive sets are like normal [attribute sets](./values.md#attribute-set), but the attributes can refer to each other.
+
+> *rec-attrset* = `rec {` [ *name* `=` *expr* `;` `]`... `}`
+
+Example:
 
 ```nix
 rec {
@@ -12,7 +15,9 @@ rec {
 }.x
 ```
 
-evaluates to `123`. Note that without `rec` the binding `x = y;` would
+This evaluates to `123`.
+
+Note that without `rec` the binding `x = y;` would
 refer to the variable `y` in the surrounding scope, if one exists, and
 would be invalid if no such variable exists. That is, in a normal
 (non-recursive) set, attributes are not added to the lexical scope; in a
@@ -33,7 +38,10 @@ will crash with an `infinite recursion encountered` error message.
 ## Let-expressions
 
 A let-expression allows you to define local variables for an expression.
-For instance,
+
+> *let-in* = `let` [ *identifier* = *expr* ]... `in` *expr*
+
+Example:
 
 ```nix
 let
@@ -42,18 +50,19 @@ let
 in x + y
 ```
 
-evaluates to `"foobar"`.
+This evaluates to `"foobar"`.
 
 ## Inheriting attributes
 
-When defining a set or in a let-expression it is often convenient to
-copy variables from the surrounding lexical scope (e.g., when you want
-to propagate attributes). This can be shortened using the `inherit`
-keyword. For instance,
+When defining an [attribute set](./values.md#attribute-set) or in a [let-expression](#let-expressions) it is often convenient to copy variables from the surrounding lexical scope (e.g., when you want to propagate attributes).
+This can be shortened using the `inherit` keyword.
+
+Example:
 
 ```nix
 let x = 123; in
-{ inherit x;
+{
+  inherit x;
   y = 456;
 }
 ```
@@ -62,23 +71,31 @@ is equivalent to
 
 ```nix
 let x = 123; in
-{ x = x;
+{
+  x = x;
   y = 456;
 }
 ```
 
-and both evaluate to `{ x = 123; y = 456; }`. (Note that this works
-because `x` is added to the lexical scope by the `let` construct.) It is
-also possible to inherit attributes from another set. For instance, in
-this fragment from `all-packages.nix`,
+and both evaluate to `{ x = 123; y = 456; }`.
+
+> **Note**
+>
+> This works because `x` is added to the lexical scope by the `let` construct.
+
+It is also possible to inherit attributes from another attribute set.
+
+Example:
+
+In this fragment from `all-packages.nix`,
 
 ```nix
 graphviz = (import ../tools/graphics/graphviz) {
   inherit fetchurl stdenv libpng libjpeg expat x11 yacc;
-  inherit (xlibs) libXaw;
+  inherit (xorg) libXaw;
 };
 
-xlibs = {
+xorg = {
   libX11 = ...;
   libXaw = ...;
   ...
@@ -92,7 +109,7 @@ libjpg = ...;
 the set used in the function call to the function defined in
 `../tools/graphics/graphviz` inherits a number of variables from the
 surrounding scope (`fetchurl` ... `yacc`), but also inherits `libXaw`
-(the X Athena Widgets) from the `xlibs` (X11 client-side libraries) set.
+(the X Athena Widgets) from the `xorg` set.
 
 Summarizing the fragment
 
@@ -115,6 +132,32 @@ a = src-set.a; b = src-set.b; c = src-set.c;
 when used while defining local variables in a let-expression or while
 defining a set.
 
+In a `let` expression, `inherit` can be used to selectively bring specific attributes of a set into scope. For example
+
+
+```nix
+let
+  x = { a = 1; b = 2; };
+  inherit (builtins) attrNames;
+in
+{
+  names = attrNames x;
+}
+```
+
+is equivalent to
+
+```nix
+let
+  x = { a = 1; b = 2; };
+in
+{
+  names = builtins.attrNames x;
+}
+```
+
+both evaluate to `{ names = [ "a" "b" ]; }`.
+
 ## Functions
 
 Functions have the following form:
@@ -129,92 +172,103 @@ three kinds of patterns:
 
   - If a pattern is a single identifier, then the function matches any
     argument. Example:
-    
+
     ```nix
     let negate = x: !x;
         concat = x: y: x + y;
     in if negate true then concat "foo" "bar" else ""
     ```
-    
+
     Note that `concat` is a function that takes one argument and returns
     a function that takes another argument. This allows partial
     parameterisation (i.e., only filling some of the arguments of a
     function); e.g.,
-    
+
     ```nix
     map (concat "foo") [ "bar" "bla" "abc" ]
     ```
-    
+
     evaluates to `[ "foobar" "foobla" "fooabc" ]`.
 
   - A *set pattern* of the form `{ name1, name2, …, nameN }` matches a
     set containing the listed attributes, and binds the values of those
     attributes to variables in the function body. For example, the
     function
-    
+
     ```nix
     { x, y, z }: z + y + x
     ```
-    
+
     can only be called with a set containing exactly the attributes `x`,
     `y` and `z`. No other attributes are allowed. If you want to allow
     additional arguments, you can use an ellipsis (`...`):
-    
+
     ```nix
     { x, y, z, ... }: z + y + x
     ```
-    
+
     This works on any set that contains at least the three named
     attributes.
-    
+
     It is possible to provide *default values* for attributes, in
     which case they are allowed to be missing. A default value is
     specified by writing `name ?  e`, where *e* is an arbitrary
     expression. For example,
-    
+
     ```nix
     { x, y ? "foo", z ? "bar" }: z + y + x
     ```
-    
+
     specifies a function that only requires an attribute named `x`, but
     optionally accepts `y` and `z`.
 
   - An `@`-pattern provides a means of referring to the whole value
     being matched:
-    
+
     ```nix
     args@{ x, y, z, ... }: z + y + x + args.a
     ```
-    
+
     but can also be written as:
-    
+
     ```nix
     { x, y, z, ... } @ args: z + y + x + args.a
     ```
-    
-    Here `args` is bound to the entire argument, which is further
-    matched against the pattern `{ x, y, z,
-            ... }`. `@`-pattern makes mainly sense with an ellipsis(`...`) as
+
+    Here `args` is bound to the argument *as passed*, which is further
+    matched against the pattern `{ x, y, z, ... }`.
+    The `@`-pattern makes mainly sense with an ellipsis(`...`) as
     you can access attribute names as `a`, using `args.a`, which was
     given as an additional attribute to the function.
-    
+
     > **Warning**
-    > 
-    > The `args@` expression is bound to the argument passed to the
-    > function which means that attributes with defaults that aren't
-    > explicitly specified in the function call won't cause an
-    > evaluation error, but won't exist in `args`.
-    > 
+    >
+    > `args@` binds the name `args` to the attribute set that is passed to the function.
+    > In particular, `args` does *not* include any default values specified with `?` in the function's set pattern.
+    >
     > For instance
-    > 
+    >
     > ```nix
     > let
-    >   function = args@{ a ? 23, ... }: args;
+    >   f = args@{ a ? 23, ... }: [ a args ];
     > in
-    >   function {}
-    > ````
-    > 
-    > will evaluate to an empty attribute set.
+    >   f {}
+    > ```
+    >
+    > is equivalent to
+    >
+    > ```nix
+    > let
+    >   f = args @ { ... }: [ (args.a or 23) args ];
+    > in
+    >   f {}
+    > ```
+    >
+    > and both expressions will evaluate to:
+    >
+    > ```nix
+    > [ 23 {} ]
+    > ```
 
 Note that functions do not have names. If you want to give them a name,
 you can bind them to an attribute, e.g.,

doc/manual/src/language/constructs/lookup-path.md

@@ -0,0 +1,27 @@
+# Lookup path
+
+> **Syntax**
+>
+> *lookup-path* = `<` *identifier* [ `/` *identifier* ]... `>`
+
+A lookup path is an identifier with an optional path suffix that resolves to a [path value](@docroot@/language/values.md#type-path) if the identifier matches a search path entry.
+
+The value of a lookup path is determined by [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath).
+
+See [`builtins.findFile`](@docroot@/language/builtins.md#builtins-findFile) for details on lookup path resolution.
+
+> **Example**
+>
+> ```nix
+> <nixpkgs>
+>```
+>
+>     /nix/var/nix/profiles/per-user/root/channels/nixpkgs
+
+> **Example**
+>
+> ```nix
+> <nixpkgs/nixos>
+>```
+>
+>     /nix/var/nix/profiles/per-user/root/channels/nixpkgs/nixos

doc/manual/src/language/derivations.md

@@ -1,161 +1,315 @@
 # Derivations
 
-The most important built-in function is `derivation`, which is used to
-describe a single derivation (a build task). It takes as input a set,
-the attributes of which specify the inputs of the build.
+The most important built-in function is `derivation`, which is used to describe a single derivation:
+a specification for running an executable on precisely defined input files to repeatably produce output files at uniquely determined file system paths.
 
-  - There must be an attribute named [`system`]{#attr-system} whose value must be a
-    string specifying a Nix system type, such as `"i686-linux"` or
-    `"x86_64-darwin"`. (To figure out your system type, run `nix -vv
-    --version`.) The build can only be performed on a machine and
-    operating system matching the system type. (Nix can automatically
-    [forward builds for other
-    platforms](../advanced-topics/distributed-builds.md) by forwarding
-    them to other machines.)
+It takes as input an attribute set, the attributes of which specify the inputs to the process.
+It outputs an attribute set, and produces a [store derivation] as a side effect of evaluation.
 
-  - There must be an attribute named `name` whose value must be a
-    string. This is used as a symbolic name for the package by
-    `nix-env`, and it is appended to the output paths of the derivation.
+[store derivation]: @docroot@/glossary.md#gloss-store-derivation
 
-  - There must be an attribute named `builder` that identifies the
-    program that is executed to perform the build. It can be either a
-    derivation or a source (a local file reference, e.g.,
-    `./builder.sh`).
+## Input attributes
 
-  - Every attribute is passed as an environment variable to the builder.
-    Attribute values are translated to environment variables as follows:
-    
-      - Strings and numbers are just passed verbatim.
-    
-      - A *path* (e.g., `../foo/sources.tar`) causes the referenced file
-        to be copied to the store; its location in the store is put in
-        the environment variable. The idea is that all sources should
-        reside in the Nix store, since all inputs to a derivation should
-        reside in the Nix store.
-    
-      - A *derivation* causes that derivation to be built prior to the
-        present derivation; its default output path is put in the
-        environment variable.
-    
-      - Lists of the previous types are also allowed. They are simply
-        concatenated, separated by spaces.
-    
-      - `true` is passed as the string `1`, `false` and `null` are
-        passed as an empty string.
+### Required
 
-  - The optional attribute `args` specifies command-line arguments to be
-    passed to the builder. It should be a list.
+- [`name`]{#attr-name} ([String](@docroot@/language/values.md#type-string))
 
-  - The optional attribute `outputs` specifies a list of symbolic
-    outputs of the derivation. By default, a derivation produces a
-    single output path, denoted as `out`. However, derivations can
-    produce multiple output paths. This is useful because it allows
-    outputs to be downloaded or garbage-collected separately. For
-    instance, imagine a library package that provides a dynamic library,
-    header files, and documentation. A program that links against the
-    library doesn’t need the header files and documentation at runtime,
-    and it doesn’t need the documentation at build time. Thus, the
-    library package could specify:
-    
-    ```nix
-    outputs = [ "lib" "headers" "doc" ];
-    ```
-    
-    This will cause Nix to pass environment variables `lib`, `headers`
-    and `doc` to the builder containing the intended store paths of each
-    output. The builder would typically do something like
-    
-    ```bash
-    ./configure \
-      --libdir=$lib/lib \
-      --includedir=$headers/include \
-      --docdir=$doc/share/doc
-    ```
-    
-    for an Autoconf-style package. You can refer to each output of a
-    derivation by selecting it as an attribute, e.g.
-    
-    ```nix
-    buildInputs = [ pkg.lib pkg.headers ];
-    ```
-    
-    The first element of `outputs` determines the *default output*.
-    Thus, you could also write
-    
-    ```nix
-    buildInputs = [ pkg pkg.headers ];
-    ```
-    
-    since `pkg` is equivalent to `pkg.lib`.
+  A symbolic name for the derivation.
+  It is added to the [store path] of the corresponding [store derivation] as well as to its [output paths](@docroot@/glossary.md#gloss-output-path).
 
-The function `mkDerivation` in the Nixpkgs standard environment is a
-wrapper around `derivation` that adds a default value for `system` and
-always uses Bash as the builder, to which the supplied builder is passed
-as a command-line argument. See the Nixpkgs manual for details.
+  [store path]: @docroot@/glossary.md#gloss-store-path
 
-The builder is executed as follows:
+  > **Example**
+  >
+  > ```nix
+  > derivation {
+  >   name = "hello";
+  >   # ...
+  > }
+  > ```
+  >
+  > The store derivation's path will be `/nix/store/<hash>-hello.drv`.
+  > The [output](#attr-outputs) paths will be of the form `/nix/store/<hash>-hello[-<output>]`
 
-  - A temporary directory is created under the directory specified by
-    `TMPDIR` (default `/tmp`) where the build will take place. The
-    current directory is changed to this directory.
+- [`system`]{#attr-system} ([String](@docroot@/language/values.md#type-string))
 
-  - The environment is cleared and set to the derivation attributes, as
-    specified above.
+  The system type on which the [`builder`](#attr-builder) executable is meant to be run.
 
-  - In addition, the following variables are set:
-    
-      - `NIX_BUILD_TOP` contains the path of the temporary directory for
-        this build.
-    
-      - Also, `TMPDIR`, `TEMPDIR`, `TMP`, `TEMP` are set to point to the
-        temporary directory. This is to prevent the builder from
-        accidentally writing temporary files anywhere else. Doing so
-        might cause interference by other processes.
-    
-      - `PATH` is set to `/path-not-set` to prevent shells from
-        initialising it to their built-in default value.
-    
-      - `HOME` is set to `/homeless-shelter` to prevent programs from
-        using `/etc/passwd` or the like to find the user's home
-        directory, which could cause impurity. Usually, when `HOME` is
-        set, it is used as the location of the home directory, even if
-        it points to a non-existent path.
-    
-      - `NIX_STORE` is set to the path of the top-level Nix store
-        directory (typically, `/nix/store`).
-    
-      - For each output declared in `outputs`, the corresponding
-        environment variable is set to point to the intended path in the
-        Nix store for that output. Each output path is a concatenation
-        of the cryptographic hash of all build inputs, the `name`
-        attribute and the output name. (The output name is omitted if
-        it’s `out`.)
+  A necessary condition for Nix to build derivations locally is that the `system` attribute matches the current [`system` configuration option].
+  It can automatically [build on other platforms](../advanced-topics/distributed-builds.md) by forwarding build requests to other machines.
 
-  - If an output path already exists, it is removed. Also, locks are
-    acquired to prevent multiple Nix instances from performing the same
-    build at the same time.
+  [`system` configuration option]: @docroot@/command-ref/conf-file.md#conf-system
 
-  - A log of the combined standard output and error is written to
-    `/nix/var/log/nix`.
+  > **Example**
+  >
+  > Declare a derivation to be built on a specific system type:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   system = "x86_64-linux";
+  >   # ...
+  > }
+  > ```
 
-  - The builder is executed with the arguments specified by the
-    attribute `args`. If it exits with exit code 0, it is considered to
-    have succeeded.
+  > **Example**
+  >
+  > Declare a derivation to be built on the system type that evaluates the expression:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   system = builtins.currentSystem;
+  >   # ...
+  > }
+  > ```
+  >
+  > [`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem) has the value of the [`system` configuration option], and defaults to the system type of the current Nix installation.
 
-  - The temporary directory is removed (unless the `-K` option was
-    specified).
+- [`builder`]{#attr-builder} ([Path](@docroot@/language/values.md#type-path) | [String](@docroot@/language/values.md#type-string))
 
-  - If the build was successful, Nix scans each output path for
-    references to input paths by looking for the hash parts of the input
-    paths. Since these are potential runtime dependencies, Nix registers
-    them as dependencies of the output paths.
+  Path to an executable that will perform the build.
 
-  - After the build, Nix sets the last-modified timestamp on all files
-    in the build result to 1 (00:00:01 1/1/1970 UTC), sets the group to
-    the default group, and sets the mode of the file to 0444 or 0555
-    (i.e., read-only, with execute permission enabled if the file was
-    originally executable). Note that possible `setuid` and `setgid`
-    bits are cleared. Setuid and setgid programs are not currently
-    supported by Nix. This is because the Nix archives used in
-    deployment have no concept of ownership information, and because it
-    makes the build result dependent on the user performing the build.
+  > **Example**
+  >
+  > Use the file located at `/bin/bash` as the builder executable:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   builder = "/bin/bash";
+  >   # ...
+  > };
+  > ```
+
+  <!-- -->
+
+  > **Example**
+  >
+  > Copy a local file to the Nix store for use as the builder executable:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   builder = ./builder.sh;
+  >   # ...
+  > };
+  > ```
+
+  <!-- -->
+
+  > **Example**
+  >
+  > Use a file from another derivation as the builder executable:
+  >
+  > ```nix
+  > let pkgs = import <nixpkgs> {}; in
+  > derivation {
+  >   # ...
+  >   builder = "${pkgs.python}/bin/python";
+  >   # ...
+  > };
+  > ```
+
+### Optional
+
+- [`args`]{#attr-args} ([List](@docroot@/language/values.md#list) of [String](@docroot@/language/values.md#type-string))
+
+  Default: `[ ]`
+
+  Command-line arguments to be passed to the [`builder`](#attr-builder) executable.
+
+  > **Example**
+  >
+  > Pass arguments to Bash to interpret a shell command:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   builder = "/bin/bash";
+  >   args = [ "-c" "echo hello world > $out" ];
+  >   # ...
+  > };
+  > ```
+
+- [`outputs`]{#attr-outputs} ([List](@docroot@/language/values.md#list) of [String](@docroot@/language/values.md#type-string))
+
+  Default: `[ "out" ]`
+
+  Symbolic outputs of the derivation.
+  Each output name is passed to the [`builder`](#attr-builder) executable as an environment variable with its value set to the corresponding [store path].
+
+  By default, a derivation produces a single output called `out`.
+  However, derivations can produce multiple outputs.
+  This allows the associated [store objects](@docroot@/glossary.md#gloss-store-object) and their [closures](@docroot@/glossary.md#gloss-closure) to be copied or garbage-collected separately.
+
+  > **Example**
+  >
+  > Imagine a library package that provides a dynamic library, header files, and documentation.
+  > A program that links against such a library doesn’t need the header files and documentation at runtime, and it doesn’t need the documentation at build time.
+  > Thus, the library package could specify:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   outputs = [ "lib" "dev" "doc" ];
+  >   # ...
+  > }
+  > ```
+  >
+  > This will cause Nix to pass environment variables `lib`, `dev`, and `doc` to the builder containing the intended store paths of each output.
+  > The builder would typically do something like
+  >
+  > ```bash
+  > ./configure \
+  >   --libdir=$lib/lib \
+  >   --includedir=$dev/include \
+  >   --docdir=$doc/share/doc
+  > ```
+  >
+  > for an Autoconf-style package.
+
+  The name of an output is combined with the name of the derivation to create the name part of the output's store path, unless it is `out`, in which case just the name of the derivation is used.
+
+  > **Example**
+  >
+  >
+  > ```nix
+  > derivation {
+  >   name = "example";
+  >   outputs = [ "lib" "dev" "doc" "out" ];
+  >   # ...
+  > }
+  > ```
+  >
+  > The store derivation path will be `/nix/store/<hash>-example.drv`.
+  > The output paths will be
+  > - `/nix/store/<hash>-example-lib`
+  > - `/nix/store/<hash>-example-dev`
+  > - `/nix/store/<hash>-example-doc`
+  > - `/nix/store/<hash>-example`
+
+  You can refer to each output of a derivation by selecting it as an attribute.
+  The first element of `outputs` determines the *default output* and ends up at the top-level.
+
+  > **Example**
+  >
+  > Select an output by attribute name:
+  >
+  > ```nix
+  > let
+  >   myPackage = derivation {
+  >     name = "example";
+  >     outputs = [ "lib" "dev" "doc" "out" ];
+  >     # ...
+  >   };
+  > in myPackage.dev
+  > ```
+  >
+  > Since `lib` is the first output, `myPackage` is equivalent to `myPackage.lib`.
+
+  <!-- FIXME: refer to the output attributes when we have one -->
+
+- See [Advanced Attributes](./advanced-attributes.md) for more, infrequently used, optional attributes.
+
+  <!-- FIXME: This should be moved here -->
+
+- Every other attribute is passed as an environment variable to the builder.
+  Attribute values are translated to environment variables as follows:
+
+    - Strings are passed unchanged.
+
+    - Integral numbers are converted to decimal notation.
+
+    - Floating point numbers are converted to simple decimal or scientific notation with a preset precision.
+
+    - A *path* (e.g., `../foo/sources.tar`) causes the referenced file
+      to be copied to the store; its location in the store is put in
+      the environment variable. The idea is that all sources should
+      reside in the Nix store, since all inputs to a derivation should
+      reside in the Nix store.
+
+    - A *derivation* causes that derivation to be built prior to the
+      present derivation. The environment variable is set to the [store path] of the derivation's default [output](#attr-outputs).
+
+    - Lists of the previous types are also allowed. They are simply
+      concatenated, separated by spaces.
+
+    - `true` is passed as the string `1`, `false` and `null` are
+      passed as an empty string.
+
+<!-- FIXME: add a section on output attributes -->
+
+## Builder execution
+
+The [`builder`](#attr-builder) is executed as follows:
+
+- A temporary directory is created under the directory specified by
+  `TMPDIR` (default `/tmp`) where the build will take place. The
+  current directory is changed to this directory.
+
+- The environment is cleared and set to the derivation attributes, as
+  specified above.
+
+- In addition, the following variables are set:
+
+  - `NIX_BUILD_TOP` contains the path of the temporary directory for
+    this build.
+
+  - Also, `TMPDIR`, `TEMPDIR`, `TMP`, `TEMP` are set to point to the
+    temporary directory. This is to prevent the builder from
+    accidentally writing temporary files anywhere else. Doing so
+    might cause interference by other processes.
+
+  - `PATH` is set to `/path-not-set` to prevent shells from
+    initialising it to their built-in default value.
+
+  - `HOME` is set to `/homeless-shelter` to prevent programs from
+    using `/etc/passwd` or the like to find the user's home
+    directory, which could cause impurity. Usually, when `HOME` is
+    set, it is used as the location of the home directory, even if
+    it points to a non-existent path.
+
+  - `NIX_STORE` is set to the path of the top-level Nix store
+    directory (typically, `/nix/store`).
+
+  - `NIX_ATTRS_JSON_FILE` & `NIX_ATTRS_SH_FILE` if `__structuredAttrs`
+    is set to `true` for the dervation. A detailed explanation of this
+    behavior can be found in the
+    [section about structured attrs](./advanced-attributes.md#adv-attr-structuredAttrs).
+
+  - For each output declared in `outputs`, the corresponding
+    environment variable is set to point to the intended path in the
+    Nix store for that output. Each output path is a concatenation
+    of the cryptographic hash of all build inputs, the `name`
+    attribute and the output name. (The output name is omitted if
+    it’s `out`.)
+
+- If an output path already exists, it is removed. Also, locks are
+  acquired to prevent multiple Nix instances from performing the same
+  build at the same time.
+
+- A log of the combined standard output and error is written to
+  `/nix/var/log/nix`.
+
+- The builder is executed with the arguments specified by the
+  attribute `args`. If it exits with exit code 0, it is considered to
+  have succeeded.
+
+- The temporary directory is removed (unless the `-K` option was
+  specified).
+
+- If the build was successful, Nix scans each output path for
+  references to input paths by looking for the hash parts of the input
+  paths. Since these are potential runtime dependencies, Nix registers
+  them as dependencies of the output paths.
+
+- After the build, Nix sets the last-modified timestamp on all files
+  in the build result to 1 (00:00:01 1/1/1970 UTC), sets the group to
+  the default group, and sets the mode of the file to 0444 or 0555
+  (i.e., read-only, with execute permission enabled if the file was
+  originally executable). Note that possible `setuid` and `setgid`
+  bits are cleared. Setuid and setgid programs are not currently
+  supported by Nix. This is because the Nix archives used in
+  deployment have no concept of ownership information, and because it
+  makes the build result dependent on the user performing the build.

doc/manual/src/language/import-from-derivation.md

@@ -0,0 +1,139 @@
+# Import From Derivation
+
+The value of a Nix expression can depend on the contents of a [store object](@docroot@/glossary.md#gloss-store-object).
+
+Passing an expression `expr` that evaluates to a [store path](@docroot@/glossary.md#gloss-store-path) to any built-in function which reads from the filesystem constitutes Import From Derivation (IFD):
+
+- [`import`](./builtins.md#builtins-import)` expr`
+- [`builtins.readFile`](./builtins.md#builtins-readFile)` expr`
+- [`builtins.readFileType`](./builtins.md#builtins-readFileType)` expr`
+- [`builtins.readDir`](./builtins.md#builtins-readDir)` expr`
+- [`builtins.pathExists`](./builtins.md#builtins-pathExists)` expr`
+- [`builtins.filterSource`](./builtins.md#builtins-filterSource)` f expr`
+- [`builtins.path`](./builtins.md#builtins-path)` { path = expr; }`
+- [`builtins.hashFile`](./builtins.md#builtins-hashFile)` t expr`
+- `builtins.scopedImport x drv`
+
+When the store path needs to be accessed, evaluation will be paused, the corresponding store object [realised], and then evaluation resumed.
+
+[realised]: @docroot@/glossary.md#gloss-realise
+
+This has performance implications:
+Evaluation can only finish when all required store objects are realised.
+Since the Nix language evaluator is sequential, it only finds store paths to read from one at a time.
+While realisation is always parallel, in this case it cannot be done for all required store paths at once, and is therefore much slower than otherwise.
+
+Realising store objects during evaluation can be disabled by setting [`allow-import-from-derivation`](../command-ref/conf-file.md#conf-allow-import-from-derivation) to `false`.
+Without IFD it is ensured that evaluation is complete and Nix can produce a build plan before starting any realisation.
+
+## Example
+
+In the following Nix expression, the inner derivation `drv` produces a file with contents `hello`.
+
+```nix
+# IFD.nix
+let
+  drv = derivation {
+    name = "hello";
+    builder = "/bin/sh";
+    args = [ "-c" "echo -n hello > $out" ];
+    system = builtins.currentSystem;
+  };
+in "${builtins.readFile drv} world"
+```
+
+```shellSession
+nix-instantiate IFD.nix --eval --read-write-mode
+```
+
+```
+building '/nix/store/348q1cal6sdgfxs8zqi9v8llrsn4kqkq-hello.drv'...
+"hello world"
+```
+
+The contents of the derivation's output have to be [realised] before they can be read with [`readFile`](./builtins.md#builtins-readFile).
+Only then evaluation can continue to produce the final result.
+
+## Illustration
+
+As a first approximation, the following data flow graph shows how evaluation and building are interleaved, if the value of a Nix expression depends on realising a [store object].
+Boxes are data structures, arrow labels are transformations.
+
+```
++----------------------+             +------------------------+
+| Nix evaluator        |             | Nix store              |
+|  .----------------.  |             |                        |
+|  | Nix expression |  |             |                        |
+|  '----------------'  |             |                        |
+|          |           |             |                        |
+|       evaluate       |             |                        |
+|          |           |             |                        |
+|          V           |             |                        |
+|    .------------.    |             |  .------------------.  |
+|    | derivation |----|-instantiate-|->| store derivation |  |
+|    '------------'    |             |  '------------------'  |
+|                      |             |           |            |
+|                      |             |        realise         |
+|                      |             |           |            |
+|                      |             |           V            |
+|  .----------------.  |             |    .--------------.    |
+|  | Nix expression |<-|----read-----|----| store object |    |
+|  '----------------'  |             |    '--------------'    |
+|          |           |             |                        |
+|       evaluate       |             |                        |
+|          |           |             |                        |
+|          V           |             |                        |
+|    .------------.    |             |                        |
+|    |   value    |    |             |                        |
+|    '------------'    |             |                        |
++----------------------+             +------------------------+
+```
+
+In more detail, the following sequence diagram shows how the expression is evaluated step by step, and where evaluation is blocked to wait for the build output to appear.
+
+```
+.-------.     .-------------.                        .---------.
+|Nix CLI|     |Nix evaluator|                        |Nix store|
+'-------'     '-------------'                        '---------'
+    |                |                                    |
+    |evaluate IFD.nix|                                    |
+    |--------------->|                                    |
+    |                |                                    |
+    |  evaluate `"${readFile drv} world"`                 |
+    |                |                                    |
+    |    evaluate `readFile drv`                          |
+    |                |                                    |
+    |   evaluate `drv` as string                          |
+    |                |                                    |
+    |                |instantiate /nix/store/...-hello.drv|
+    |                |----------------------------------->|
+    |                :                                    |
+    |                :  realise /nix/store/...-hello.drv  |
+    |                :----------------------------------->|
+    |                :                                    |
+    |                                                     |--------.
+    |                :                                    |        |
+    |      (evaluation blocked)                           |  echo hello > $out
+    |                :                                    |        |
+    |                                                     |<-------'
+    |                :        /nix/store/...-hello        |
+    |                |<-----------------------------------|
+    |                |                                    |
+    |  resume `readFile /nix/store/...-hello`             |
+    |                |                                    |
+    |                |   readFile /nix/store/...-hello    |
+    |                |----------------------------------->|
+    |                |                                    |
+    |                |               hello                |
+    |                |<-----------------------------------|
+    |                |                                    |
+    |      resume `"${"hello"} world"`                    |
+    |                |                                    |
+    |        resume `"hello world"`                       |
+    |                |                                    |
+    | "hello world"  |                                    |
+    |<---------------|                                    |
+.-------.     .-------------.                        .---------.
+|Nix CLI|     |Nix evaluator|                        |Nix store|
+'-------'     '-------------'                        '---------'
+```

doc/manual/src/language/index.md

@@ -1,12 +1,11 @@
 # Nix Language
 
-The Nix language is
+The Nix language is designed for conveniently creating and composing *derivations* – precise descriptions of how contents of existing files are used to derive new files.
+It is:
 
 - *domain-specific*
 
-  It only exists for the Nix package manager:
-  to describe packages and configurations as well as their variants and compositions.
-  It is not intended for general purpose use.
+  It comes with [built-in functions](@docroot@/language/builtins.md) to integrate with the Nix store, which manages files and performs the derivations declared in the Nix language.
 
 - *declarative*
 
@@ -25,7 +24,7 @@ The Nix language is
 
 - *lazy*
 
-  Expressions are only evaluated when their value is needed.
+  Values are only computed when they are needed.
 
 - *dynamically typed*
 
@@ -84,7 +83,8 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A multi-line string. Strips common prefixed whitespace. Evaluates to `"multi\n line\n  string"`.
+   <!-- FIXME: using two no-break spaces, because apparently mdBook swallows the second regular space! -->
+   A multi-line string. Strips common prefixed whitespace. Evaluates to `"multi\n line\n  string"`.
 
   </td>
  </tr>

doc/manual/src/language/operators.md

@@ -25,7 +25,7 @@
 | Inequality                             | *expr* `!=` *expr*                         | none          | 11         |
 | Logical conjunction (`AND`)            | *bool* `&&` *bool*                         | left          | 12         |
 | Logical disjunction (`OR`)             | *bool* <code>\|\|</code> *bool*            | left          | 13         |
-| [Logical implication]                  | *bool* `->` *bool*                         | none          | 14         |
+| [Logical implication]                  | *bool* `->` *bool*                         | right         | 14         |
 
 [string]: ./values.md#type-string
 [path]: ./values.md#type-path
@@ -35,31 +35,38 @@
 
 ## Attribute selection
 
+> **Syntax**
+>
+> *attrset* `.` *attrpath* \[ `or` *expr* \]
+
 Select the attribute denoted by attribute path *attrpath* from [attribute set] *attrset*.
 If the attribute doesn’t exist, return the *expr* after `or` if provided, otherwise abort evaluation.
 
-<!-- FIXME: the following should to into its own language syntax section, but that needs more work to fit in well -->
+An attribute path is a dot-separated list of [attribute names](./values.md#attribute-set).
 
-An attribute path is a dot-separated list of attribute names.
-An attribute name can be an identifier or a string.
-
-> *attrpath* = *name* [ `.` *name* ]... \
-> *name* = *identifier* | *string* \
-> *identifier* ~ `[a-zA-Z_][a-zA-Z0-9_'-]*`
+> **Syntax**
+>
+> *attrpath* = *name* [ `.` *name* ]...
 
 [Attribute selection]: #attribute-selection
 
 ## Has attribute
 
+> **Syntax**
+>
 > *attrset* `?` *attrpath*
 
 Test whether [attribute set] *attrset* contains the attribute denoted by *attrpath*.
 The result is a [Boolean] value.
 
+See also: [`builtins.hasAttr`](@docroot@/language/builtins.md#builtins-hasAttr)
+
 [Boolean]: ./values.md#type-boolean
 
 [Has attribute]: #has-attribute
 
+After evaluating *attrset* and *attrpath*, the computational complexity is O(log(*n*)) for *n* attributes in the *attrset*
+
 ## Arithmetic
 
 Numbers are type-compatible:
@@ -73,6 +80,8 @@ The `+` operator is overloaded to also work on strings and paths.
 
 ## String concatenation
 
+> **Syntax**
+>
 > *string* `+` *string*
 
 Concatenate two [string]s and merge their string contexts.
@@ -81,6 +90,8 @@ Concatenate two [string]s and merge their string contexts.
 
 ## Path concatenation
 
+> **Syntax**
+>
 > *path* `+` *path*
 
 Concatenate two [path]s.
@@ -90,6 +101,8 @@ The result is a path.
 
 ## Path and string concatenation
 
+> **Syntax**
+>
 > *path* + *string*
 
 Concatenate *[path]* with *[string]*.
@@ -103,6 +116,8 @@ The result is a path.
 
 ## String and path concatenation
 
+> **Syntax**
+>
 > *string* + *path*
 
 Concatenate *[string]* with *[path]*.
@@ -120,6 +135,8 @@ The result is a string.
 
 ## Update
 
+> **Syntax**
+>
 > *attrset1* // *attrset2*
 
 Update [attribute set] *attrset1* with names and values from *attrset2*.

doc/manual/src/language/string-interpolation.md

@@ -1,19 +1,12 @@
 # String interpolation
 
-String interpolation is a language feature where a [string], [path], or [attribute name] can contain expressions enclosed in `${ }` (dollar-sign with curly brackets).
+String interpolation is a language feature where a [string], [path], or [attribute name][attribute set] can contain expressions enclosed in `${ }` (dollar-sign with curly brackets).
 
-Such a string is an *interpolated string*, and an expression inside is an *interpolated expression*.
-
-Interpolated expressions must evaluate to one of the following:
-
-- a [string]
-- a [path]
-- a [derivation]
+Such a construct is called *interpolated string*, and the expression inside is an [interpolated expression](#interpolated-expression).
 
 [string]: ./values.md#type-string
 [path]: ./values.md#type-path
-[attribute name]: ./values.md#attribute-set
-[derivation]: ../glossary.md#gloss-derivation
+[attribute set]: ./values.md#attribute-set
 
 ## Examples
 
@@ -70,13 +63,136 @@ you can instead write
 
 ### Attribute name
 
-Attribute names can be created dynamically with string interpolation:
+<!--
+FIXME: these examples are redundant with the main page on attribute sets.
+figure out what to do about that
+-->
 
-```nix
-let name = "foo"; in
-{
-  ${name} = "bar";
-}
-```
+Attribute names can be interpolated strings.
 
-    { foo = "bar"; }
+> **Example**
+>
+> ```nix
+> let name = "foo"; in
+> { ${name} = 123; }
+> ```
+>
+>     { foo = 123; }
+
+Attributes can be selected with interpolated strings.
+
+> **Example**
+>
+> ```nix
+> let name = "foo"; in
+> { foo = 123; }.${name}
+> ```
+>
+>     123
+
+# Interpolated expression
+
+An expression that is interpolated must evaluate to one of the following:
+
+- a [string]
+- a [path]
+- an [attribute set] that has a `__toString` attribute or an `outPath` attribute
+
+  - `__toString` must be a function that takes the attribute set itself and returns a string
+  - `outPath` must be a string
+
+  This includes [derivations](./derivations.md) or [flake inputs](@docroot@/command-ref/new-cli/nix3-flake.md#flake-inputs) (experimental).
+
+A string interpolates to itself.
+
+A path in an interpolated expression is first copied into the Nix store, and the resulting string is the [store path] of the newly created [store object](../glossary.md#gloss-store-object).
+
+[store path]: ../glossary.md#gloss-store-path
+
+> **Example**
+>
+> ```console
+> $ mkdir foo
+> ```
+>
+> Reference the empty directory in an interpolated expression:
+>
+> ```nix
+> "${./foo}"
+> ```
+>
+>     "/nix/store/2hhl2nz5v0khbn06ys82nrk99aa1xxdw-foo"
+
+A derivation interpolates to the [store path] of its first [output](./derivations.md#attr-outputs).
+
+> **Example**
+>
+> ```nix
+> let
+>   pkgs = import <nixpkgs> {};
+> in
+> "${pkgs.hello}"
+> ```
+>
+>     "/nix/store/4xpfqf29z4m8vbhrqcz064wfmb46w5r7-hello-2.12.1"
+
+An attribute set interpolates to the return value of the function in the `__toString` applied to the attribute set itself.
+
+> **Example**
+>
+> ```nix
+> let
+>   a = {
+>     value = 1;
+>     __toString = self: toString (self.value + 1);
+>   };
+> in
+> "${a}"
+> ```
+>
+>     "2"
+
+An attribute set also interpolates to the value of its `outPath` attribute.
+
+> **Example**
+>
+> ```nix
+> let
+>   a = { outPath = "foo"; };
+> in
+> "${a}"
+> ```
+>
+>     "foo"
+
+If both `__toString` and `outPath` are present in an attribute set, `__toString` takes precedence.
+
+> **Example**
+>
+> ```nix
+> let
+>   a = { __toString = _: "yes"; outPath = throw "no"; };
+> in
+> "${a}"
+> ```
+>
+>     "yes"
+
+If neither is present, an error is thrown.
+
+> **Example**
+>
+> ```nix
+> let
+>   a = {};
+> in
+> "${a}"
+> ```
+>
+>     error: cannot coerce a set to a string
+>
+>            at «string»:4:2:
+>
+>                 3| in
+>                 4| "${a}"
+>                  |  ^

doc/manual/src/language/values.md

@@ -107,29 +107,24 @@
   e.g. `~/foo` would be equivalent to `/home/edolstra/foo` for a user
   whose home directory is `/home/edolstra`.
 
-  Paths can also be specified between angle brackets, e.g.
-  `<nixpkgs>`. This means that the directories listed in the
-  environment variable `NIX_PATH` will be searched for the given file
-  or directory name.
-
-  When an [interpolated string][string interpolation] evaluates to a path, the path is first copied into the Nix store and the resulting string is the [store path] of the newly created [store object].
-
-  [store path]: ../glossary.md#gloss-store-path
-  [store object]: ../glossary.md#gloss-store-object
-
   For instance, evaluating `"${./foo.txt}"` will cause `foo.txt` in the current directory to be copied into the Nix store and result in the string `"/nix/store/<hash>-foo.txt"`.
 
   Note that the Nix language assumes that all input files will remain _unchanged_ while  evaluating a Nix expression.
   For example, assume you used a file path in an interpolated string during a `nix repl` session.
-  Later in the same session, after having changed the file contents, evaluating the interpolated string with the file path again might not return a new store path, since Nix might not re-read the file contents.
+  Later in the same session, after having changed the file contents, evaluating the interpolated string with the file path again might not return a new [store path], since Nix might not re-read the file contents.
 
-  Paths themselves, except those in angle brackets (`< >`), support [string interpolation].
+  [store path]: ../glossary.md#gloss-store-path
+
+  Paths can include [string interpolation] and can themselves be [interpolated in other expressions].
+  [interpolated in other expressions]: ./string-interpolation.md#interpolated-expressions
 
   At least one slash (`/`) must appear *before* any interpolated expression for the result to be recognized as a path.
 
   `a.${foo}/b.${bar}` is a syntactically valid division operation.
   `./a.${foo}/b.${bar}` is a path.
 
+  [Lookup paths](./constructs/lookup-path.md) such as `<nixpkgs>` resolve to path values.
+
 - <a id="type-boolean" href="#type-boolean">Boolean</a>
 
   *Booleans* with values `true` and `false`.
@@ -164,9 +159,21 @@ Note that lists are only lazy in values, and they are strict in length.
 
 An attribute set is a collection of name-value-pairs (called *attributes*) enclosed in curly brackets (`{ }`).
 
+An attribute name can be an identifier or a [string](#string).
+An identifier must start with a letter (`a-z`, `A-Z`) or underscore (`_`), and can otherwise contain letters (`a-z`, `A-Z`), numbers (`0-9`), underscores (`_`), apostrophes (`'`), or dashes (`-`).
+
+> **Syntax**
+>
+> *name* = *identifier* | *string* \
+> *identifier* ~ `[a-zA-Z_][a-zA-Z0-9_'-]*`
+
 Names and values are separated by an equal sign (`=`).
 Each value is an arbitrary expression terminated by a semicolon (`;`).
 
+> **Syntax**
+>
+> *attrset* = `{` [ *name* `=` *expr* `;` ]... `}`
+
 Attributes can appear in any order.
 An attribute name may only occur once.
 
@@ -182,15 +189,19 @@ Example:
 
 This defines a set with attributes named `x`, `text`, `y`.
 
-Attributes can be selected from a set using the `.` operator. For
-instance,
+Attributes can be accessed with the [`.` operator](./operators.md#attribute-selection).
+
+Example:
 
 ```nix
 { a = "Foo"; b = "Bar"; }.a
 ```
 
-evaluates to `"Foo"`. It is possible to provide a default value in an
-attribute selection using the `or` keyword:
+This evaluates to `"Foo"`.
+
+It is possible to provide a default value in an attribute selection using the `or` keyword.
+
+Example:
 
 ```nix
 { a = "Foo"; b = "Bar"; }.c or "Xyzzy"

doc/manual/src/package-management/basic-package-mgmt.md

@@ -1,179 +0,0 @@
-# Basic Package Management
-
-The main command for package management is
-[`nix-env`](../command-ref/nix-env.md).  You can use it to install,
-upgrade, and erase packages, and to query what packages are installed
-or are available for installation.
-
-In Nix, different users can have different “views” on the set of
-installed applications. That is, there might be lots of applications
-present on the system (possibly in many different versions), but users
-can have a specific selection of those active — where “active” just
-means that it appears in a directory in the user’s `PATH`. Such a view
-on the set of installed applications is called a *user environment*,
-which is just a directory tree consisting of symlinks to the files of
-the active applications.
-
-Components are installed from a set of *Nix expressions* that tell Nix
-how to build those packages, including, if necessary, their
-dependencies. There is a collection of Nix expressions called the
-Nixpkgs package collection that contains packages ranging from basic
-development stuff such as GCC and Glibc, to end-user applications like
-Mozilla Firefox. (Nix is however not tied to the Nixpkgs package
-collection; you could write your own Nix expressions based on Nixpkgs,
-or completely new ones.)
-
-You can manually download the latest version of Nixpkgs from
-<https://github.com/NixOS/nixpkgs>. However, it’s much more
-convenient to use the Nixpkgs [*channel*](channels.md), since it makes
-it easy to stay up to date with new versions of Nixpkgs. Nixpkgs is
-automatically added to your list of “subscribed” channels when you
-install Nix. If this is not the case for some reason, you can add it
-as follows:
-
-```console
-$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
-$ nix-channel --update
-```
-
-> **Note**
-> 
-> On NixOS, you’re automatically subscribed to a NixOS channel
-> corresponding to your NixOS major release (e.g.
-> <http://nixos.org/channels/nixos-21.11>). A NixOS channel is identical
-> to the Nixpkgs channel, except that it contains only Linux binaries
-> and is updated only if a set of regression tests succeed.
-
-You can view the set of available packages in Nixpkgs:
-
-```console
-$ nix-env --query --available --attr-path
-nixpkgs.aterm                       aterm-2.2
-nixpkgs.bash                        bash-3.0
-nixpkgs.binutils                    binutils-2.15
-nixpkgs.bison                       bison-1.875d
-nixpkgs.blackdown                   blackdown-1.4.2
-nixpkgs.bzip2                       bzip2-1.0.2
-…
-```
-
-The flag `-q` specifies a query operation, `-a` means that you want
-to show the “available” (i.e., installable) packages, as opposed to the
-installed packages, and `-P` prints the attribute paths that can be used
-to unambiguously select a package for installation (listed in the first column).
-If you downloaded Nixpkgs yourself, or if you checked it out from GitHub,
-then you need to pass the path to your Nixpkgs tree using the `-f` flag:
-
-```console
-$ nix-env --query --available --attr-path --file /path/to/nixpkgs
-aterm                               aterm-2.2
-bash                                bash-3.0
-…
-```
-
-where */path/to/nixpkgs* is where you’ve unpacked or checked out
-Nixpkgs.
-
-You can filter the packages by name:
-
-```console
-$ nix-env --query --available --attr-path firefox
-nixpkgs.firefox-esr                 firefox-91.3.0esr
-nixpkgs.firefox                     firefox-94.0.1
-```
-
-and using regular expressions:
-
-```console
-$ nix-env --query --available --attr-path 'firefox.*'
-```
-
-It is also possible to see the *status* of available packages, i.e.,
-whether they are installed into the user environment and/or present in
-the system:
-
-```console
-$ nix-env --query --available --attr-path --status
-…
--PS  nixpkgs.bash                bash-3.0
---S  nixpkgs.binutils            binutils-2.15
-IPS  nixpkgs.bison               bison-1.875d
-…
-```
-
-The first character (`I`) indicates whether the package is installed in
-your current user environment. The second (`P`) indicates whether it is
-present on your system (in which case installing it into your user
-environment would be a very quick operation). The last one (`S`)
-indicates whether there is a so-called *substitute* for the package,
-which is Nix’s mechanism for doing binary deployment. It just means that
-Nix knows that it can fetch a pre-built package from somewhere
-(typically a network server) instead of building it locally.
-
-You can install a package using `nix-env --install --attr `. For instance,
-
-```console
-$ nix-env --install --attr nixpkgs.subversion
-```
-
-will install the package called `subversion` from `nixpkgs` channel (which is, of course, the
-[Subversion version management system](http://subversion.tigris.org/)).
-
-> **Note**
-> 
-> When you ask Nix to install a package, it will first try to get it in
-> pre-compiled form from a *binary cache*. By default, Nix will use the
-> binary cache <https://cache.nixos.org>; it contains binaries for most
-> packages in Nixpkgs. Only if no binary is available in the binary
-> cache, Nix will build the package from source. So if `nix-env
-> -iA nixpkgs.subversion` results in Nix building stuff from source, then either
-> the package is not built for your platform by the Nixpkgs build
-> servers, or your version of Nixpkgs is too old or too new. For
-> instance, if you have a very recent checkout of Nixpkgs, then the
-> Nixpkgs build servers may not have had a chance to build everything
-> and upload the resulting binaries to <https://cache.nixos.org>. The
-> Nixpkgs channel is only updated after all binaries have been uploaded
-> to the cache, so if you stick to the Nixpkgs channel (rather than
-> using a Git checkout of the Nixpkgs tree), you will get binaries for
-> most packages.
-
-Naturally, packages can also be uninstalled. Unlike when installing, you will
-need to use the derivation name (though the version part can be omitted),
-instead of the attribute path, as `nix-env` does not record which attribute
-was used for installing:
-
-```console
-$ nix-env --uninstall subversion
-```
-
-Upgrading to a new version is just as easy. If you have a new release of
-Nix Packages, you can do:
-
-```console
-$ nix-env --upgrade --attr nixpkgs.subversion
-```
-
-This will *only* upgrade Subversion if there is a “newer” version in the
-new set of Nix expressions, as defined by some pretty arbitrary rules
-regarding ordering of version numbers (which generally do what you’d
-expect of them). To just unconditionally replace Subversion with
-whatever version is in the Nix expressions, use `-i` instead of `-u`;
-`-i` will remove whatever version is already installed.
-
-You can also upgrade all packages for which there are newer versions:
-
-```console
-$ nix-env --upgrade
-```
-
-Sometimes it’s useful to be able to ask what `nix-env` would do, without
-actually doing it. For instance, to find out what packages would be
-upgraded by `nix-env --upgrade `, you can do
-
-```console
-$ nix-env --upgrade --dry-run
-(dry run; not doing anything)
-upgrading `libxslt-1.1.0' to `libxslt-1.1.10'
-upgrading `graphviz-1.10' to `graphviz-1.12'
-upgrading `coreutils-5.0' to `coreutils-5.2.1'
-```

doc/manual/src/package-management/channels.md

@@ -1,50 +0,0 @@
-# Channels
-
-If you want to stay up to date with a set of packages, it’s not very
-convenient to manually download the latest set of Nix expressions for
-those packages and upgrade using `nix-env`. Fortunately, there’s a
-better way: *Nix channels*.
-
-A Nix channel is just a URL that points to a place that contains a set
-of Nix expressions and a manifest. Using the command
-[`nix-channel`](../command-ref/nix-channel.md) you can automatically
-stay up to date with whatever is available at that URL.
-
-To see the list of official NixOS channels, visit
-<https://nixos.org/channels>.
-
-You can “subscribe” to a channel using `nix-channel --add`, e.g.,
-
-```console
-$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
-```
-
-subscribes you to a channel that always contains that latest version of
-the Nix Packages collection. (Subscribing really just means that the URL
-is added to the file `~/.nix-channels`, where it is read by subsequent
-calls to `nix-channel
---update`.) You can “unsubscribe” using `nix-channel
---remove`:
-
-```console
-$ nix-channel --remove nixpkgs
-```
-
-To obtain the latest Nix expressions available in a channel, do
-
-```console
-$ nix-channel --update
-```
-
-This downloads and unpacks the Nix expressions in every channel
-(downloaded from `url/nixexprs.tar.bz2`). It also makes the union of
-each channel’s Nix expressions available by default to `nix-env`
-operations (via the symlink `~/.nix-defexpr/channels`). Consequently,
-you can then say
-
-```console
-$ nix-env --upgrade
-```
-
-to upgrade all packages in your profile to the latest versions available
-in the subscribed channels.

doc/manual/src/package-management/s3-substituter.md

@@ -1,115 +0,0 @@
-# Serving a Nix store via S3
-
-Nix has [built-in support](@docroot@/command-ref/new-cli/nix3-help-stores.md#s3-binary-cache-store)
-for storing and fetching store paths from
-Amazon S3 and S3-compatible services. This uses the same *binary*
-cache mechanism that Nix usually uses to fetch prebuilt binaries from
-[cache.nixos.org](https://cache.nixos.org/).
-
-In this example we will use the bucket named `example-nix-cache`.
-
-## Anonymous Reads to your S3-compatible binary cache
-
-If your binary cache is publicly accessible and does not require
-authentication, the simplest and easiest way to use Nix with your S3
-compatible binary cache is to use the HTTP URL for that cache.
-
-For AWS S3 the binary cache URL for example bucket will be exactly
-<https://example-nix-cache.s3.amazonaws.com> or
-<s3://example-nix-cache>. For S3 compatible binary caches, consult that
-cache's documentation.
-
-Your bucket will need the following bucket policy:
-
-```json
-{
-    "Id": "DirectReads",
-    "Version": "2012-10-17",
-    "Statement": [
-        {
-            "Sid": "AllowDirectReads",
-            "Action": [
-                "s3:GetObject",
-                "s3:GetBucketLocation"
-            ],
-            "Effect": "Allow",
-            "Resource": [
-                "arn:aws:s3:::example-nix-cache",
-                "arn:aws:s3:::example-nix-cache/*"
-            ],
-            "Principal": "*"
-        }
-    ]
-}
-```
-
-## Authenticated Reads to your S3 binary cache
-
-For AWS S3 the binary cache URL for example bucket will be exactly
-<s3://example-nix-cache>.
-
-Nix will use the [default credential provider
-chain](https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html)
-for authenticating requests to Amazon S3.
-
-Nix supports authenticated reads from Amazon S3 and S3 compatible binary
-caches.
-
-Your bucket will need a bucket policy allowing the desired users to
-perform the `s3:GetObject` and `s3:GetBucketLocation` action on all
-objects in the bucket. The [anonymous policy given
-above](#anonymous-reads-to-your-s3-compatible-binary-cache) can be
-updated to have a restricted `Principal` to support this.
-
-## Authenticated Writes to your S3-compatible binary cache
-
-Nix support fully supports writing to Amazon S3 and S3 compatible
-buckets. The binary cache URL for our example bucket will be
-<s3://example-nix-cache>.
-
-Nix will use the [default credential provider
-chain](https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html)
-for authenticating requests to Amazon S3.
-
-Your account will need the following IAM policy to upload to the cache:
-
-```json
-{
-  "Version": "2012-10-17",
-  "Statement": [
-    {
-      "Sid": "UploadToCache",
-      "Effect": "Allow",
-      "Action": [
-        "s3:AbortMultipartUpload",
-        "s3:GetBucketLocation",
-        "s3:GetObject",
-        "s3:ListBucket",
-        "s3:ListBucketMultipartUploads",
-        "s3:ListMultipartUploadParts",
-        "s3:PutObject"
-      ],
-      "Resource": [
-        "arn:aws:s3:::example-nix-cache",
-        "arn:aws:s3:::example-nix-cache/*"
-      ]
-    }
-  ]
-}
-```
-
-## Examples
-
-To upload with a specific credential profile for Amazon S3:
-
-```console
-$ nix copy nixpkgs.hello \
-  --to 's3://example-nix-cache?profile=cache-upload&region=eu-west-2'
-```
-
-To upload to an S3-compatible binary cache:
-
-```console
-$ nix copy nixpkgs.hello --to \
-  's3://example-nix-cache?profile=cache-upload&scheme=https&endpoint=minio.example.com'
-```

doc/manual/src/protocols/derivation-aterm.md

@@ -0,0 +1,19 @@
+# Derivation "ATerm" file format
+
+For historical reasons, [derivations](@docroot@/glossary.md#gloss-store-derivation) are stored on-disk in [ATerm](https://homepages.cwi.nl/~daybuild/daily-books/technology/aterm-guide/aterm-guide.html) format.
+
+Derivations are serialised in one of the following formats:
+
+- ```
+  Derive(...)
+  ```
+
+  For all stable derivations.
+
+- ```
+  DrvWithVersion(<version-string>, ...)
+  ```
+
+  The only `version-string`s that are in use today are for [experimental features](@docroot@/contributing/experimental-features.md):
+
+  - `"xp-dyn-drv"` for the [`dynamic-derivations`](@docroot@/contributing/experimental-features.md#xp-feature-dynamic-derivations) experimental feature.

doc/manual/src/protocols/protocols.md

@@ -0,0 +1,4 @@
+# Protocols
+
+This chapter documents various developer-facing interfaces provided by
+Nix.

doc/manual/src/protocols/tarball-fetcher.md

@@ -0,0 +1,42 @@
+# Lockable HTTP Tarball Protocol
+
+Tarball flakes can be served as regular tarballs via HTTP or the file
+system (for `file://` URLs). Unless the server implements the Lockable
+HTTP Tarball protocol, it is the responsibility of the user to make sure that
+the URL always produces the same tarball contents.
+
+An HTTP server can return an "immutable" HTTP URL appropriate for lock
+files. This allows users to specify a tarball flake input in
+`flake.nix` that requests the latest version of a flake
+(e.g. `https://example.org/hello/latest.tar.gz`), while `flake.lock`
+will record a URL whose contents will not change
+(e.g. `https://example.org/hello/<revision>.tar.gz`). To do so, the
+server must return an [HTTP `Link` header](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Link) with the `rel` attribute set to
+`immutable`, as follows:
+
+```
+Link: <flakeref>; rel="immutable"
+```
+
+(Note the required `<` and `>` characters around *flakeref*.)
+
+*flakeref* must be a tarball flakeref. It can contain the tarball flake attributes
+`narHash`, `rev`, `revCount` and `lastModified`. If `narHash` is included, its
+value must be the NAR hash of the unpacked tarball (as computed via
+`nix hash path`). Nix checks the contents of the returned tarball
+against the `narHash` attribute. The `rev` and `revCount` attributes
+are useful when the tarball flake is a mirror of a fetcher type that
+has those attributes, such as Git or GitHub. They are not checked by
+Nix.
+
+```
+Link: <https://example.org/hello/442793d9ec0584f6a6e82fa253850c8085bb150a.tar.gz
+  ?rev=442793d9ec0584f6a6e82fa253850c8085bb150a
+  &revCount=835
+  &narHash=sha256-GUm8Uh/U74zFCwkvt9Mri4DSM%2BmHj3tYhXUkYpiv31M%3D>; rel="immutable"
+```
+
+(The linebreaks in this example are for clarity and must not be included in the actual response.)
+
+For tarball flakes, the value of the `lastModified` flake attribute is
+defined as the timestamp of the newest file inside the tarball.

doc/manual/src/release-notes/release-notes.md

@@ -1 +1,12 @@
 # Nix Release Notes
+
+Nix has a release cycle of roughly 6 weeks.
+Notable changes and additions are announced in the release notes for each version.
+
+Bugfixes can be backported on request to previous Nix releases.
+We typically backport only as far back as the Nix version used in the latest NixOS release, which is announced in the [NixOS release notes](https://nixos.org/manual/nixos/stable/release-notes.html#ch-release-notes).
+
+Backports never skip releases.
+If a feature is backported to version `x.y`, it must also be available in version `x.(y+1)`.
+This ensures that upgrading from an older version with backports is still safe and no backported functionality will go missing.
+

doc/manual/src/release-notes/rl-2.12.md

@@ -2,7 +2,6 @@
 
 * On Linux, Nix can now run builds in a user namespace where they run
   as root (UID 0) and have 65,536 UIDs available.
-  <!-- FIXME: move this to its own section about system features -->
   This is primarily useful for running containers such as `systemd-nspawn`
   inside a Nix build. For an example, see [`tests/systemd-nspawn/nix`][nspawn].
 

doc/manual/src/release-notes/rl-2.17.md

@@ -0,0 +1,42 @@
+# Release 2.17 (2023-07-24)
+
+* [`nix-channel`](../command-ref/nix-channel.md) now supports a `--list-generations` subcommand.
+
+* The function [`builtins.fetchClosure`](../language/builtins.md#builtins-fetchClosure) can now fetch input-addressed paths in [pure evaluation mode](../command-ref/conf-file.md#conf-pure-eval), as those are not impure.
+
+* Nix now allows unprivileged/[`allowed-users`](../command-ref/conf-file.md#conf-allowed-users) to sign paths.
+  Previously, only [`trusted-users`](../command-ref/conf-file.md#conf-trusted-users) users could sign paths.
+
+* Nested dynamic attributes are now merged correctly by the parser. For example:
+
+  ```nix
+  {
+    nested = {
+      foo = 1;
+    };
+    nested = {
+      ${"ba" + "r"} = 2;
+    };
+  }
+  ```
+
+  This used to silently discard `nested.bar`, but now behaves as one would expect and evaluates to:
+
+  ```nix
+  { nested = { bar = 2; foo = 1; }; }
+  ```
+
+  Note that the feature of merging multiple *full declarations* of attribute sets like `nested` in the example is of questionable value.
+  It allows writing expressions that are very hard to read, for instance when there are many lines of code between two declarations of the same attribute.
+  This has been around for a long time and is therefore supported for backwards compatibility, but should not be relied upon.
+
+  Instead, consider using the *nested attribute path* syntax:
+
+  ```nix
+  {
+    nested.foo = 1;
+    nested.${"ba" + "r"} = 2;
+  }
+  ```
+
+* Tarball flakes can now redirect to an "immutable" URL that will be recorded in lock files. This allows the use of "mutable" tarball URLs like `https://example.org/hello/latest.tar.gz` in flakes. See the [tarball fetcher](../protocols/tarball-fetcher.md) for details.

doc/manual/src/release-notes/rl-2.18.md

@@ -0,0 +1,28 @@
+# Release 2.18 (2023-09-20)
+
+- Two new builtin functions,
+  [`builtins.parseFlakeRef`](@docroot@/language/builtins.md#builtins-parseFlakeRef)
+  and
+  [`builtins.flakeRefToString`](@docroot@/language/builtins.md#builtins-flakeRefToString),
+  have been added.
+  These functions are useful for converting between flake references encoded as attribute sets and URLs.
+
+- [`builtins.toJSON`](@docroot@/language/builtins.md#builtins-parseFlakeRef) now prints [--show-trace](@docroot@/command-ref/conf-file.html#conf-show-trace) items for the path in which it finds an evaluation error.
+
+- Error messages regarding malformed input to [`nix derivation add`](@docroot@/command-ref/new-cli/nix3-derivation-add.md) are now clearer and more detailed.
+
+- The `discard-references` feature has been stabilized.
+  This means that the
+  [unsafeDiscardReferences](@docroot@/contributing/experimental-features.md#xp-feature-discard-references)
+  attribute is no longer guarded by an experimental flag and can be used
+  freely.
+
+- The JSON output for derived paths which are store paths is now a string, not an object with a single `path` field.
+  This only affects `nix-build --json` when "building" non-derivation things like fetched sources, which is a no-op.
+
+- A new builtin [`outputOf`](@docroot@/language/builtins.md#builtins-outputOf) has been added.
+  It is part of the [`dynamic-derivations`](@docroot@/contributing/experimental-features.md#xp-feature-dynamic-derivations) experimental feature.
+
+- Flake follow paths at depths greater than 2 are now handled correctly, preventing "follows a non-existent input" errors.
+
+- [`nix-store --query`](@docroot@/command-ref/nix-store/query.md) gained a new type of query: `--valid-derivers`. It returns all `.drv` files in the local store that *can be* used to build the output passed in argument. This is in contrast to `--deriver`, which returns the single `.drv` file that *was actually* used to build the output passed in argument. In case the output was substituted from a binary cache, this `.drv` file may only exist on said binary cache and not locally.

doc/manual/src/release-notes/rl-2.19.md

@@ -0,0 +1,77 @@
+# Release 2.19 (2023-11-17)
+
+- The experimental `nix` command can now act as a [shebang interpreter](@docroot@/command-ref/new-cli/nix.md#shebang-interpreter)
+  by appending the contents of any `#! nix` lines and the script's location into a single call.
+
+- [URL flake references](@docroot@/command-ref/new-cli/nix3-flake.md#flake-references) now support [percent-encoded](https://datatracker.ietf.org/doc/html/rfc3986#section-2.1) characters.
+
+- [Path-like flake references](@docroot@/command-ref/new-cli/nix3-flake.md#path-like-syntax) now accept arbitrary unicode characters (except `#` and `?`).
+
+- The experimental feature `repl-flake` is no longer needed, as its functionality is now part of the `flakes` experimental feature. To get the previous behavior, use the `--file/--expr` flags accordingly.
+
+- There is a new flake installable syntax `flakeref#.attrPath` where the "." prefix specifies that `attrPath` is interpreted from the root of the flake outputs, with no searching of default attribute prefixes like `packages.<SYSTEM>` or `legacyPackages.<SYSTEM>`.
+
+- Nix adds `apple-virt` to the default system features on macOS systems that support virtualization. This is similar to what's done for the `kvm` system feature on Linux hosts.
+
+- Add a new built-in function [`builtins.convertHash`](@docroot@/language/builtins.md#builtins-convertHash).
+
+- `nix-shell` shebang lines now support single-quoted arguments.
+
+- `builtins.fetchTree` is now its own experimental feature, [`fetch-tree`](@docroot@/contributing/experimental-features.md#xp-fetch-tree).
+  As described in the documentation for that feature, this is because we anticipate polishing it and then stabilizing it before the rest of flakes.
+
+- The interface for creating and updating lock files has been overhauled:
+
+  - [`nix flake lock`](@docroot@/command-ref/new-cli/nix3-flake-lock.md) only creates lock files and adds missing inputs now.
+    It will *never* update existing inputs.
+
+  - [`nix flake update`](@docroot@/command-ref/new-cli/nix3-flake-update.md) does the same, but *will* update inputs.
+    - Passing no arguments will update all inputs of the current flake, just like it already did.
+    - Passing input names as arguments will ensure only those are updated. This replaces the functionality of `nix flake lock --update-input`
+    - To operate on a flake outside the current directory, you must now pass `--flake path/to/flake`.
+
+  - The flake-specific flags `--recreate-lock-file` and `--update-input` have been removed from all commands operating on installables.
+    They are superceded by `nix flake update`.
+
+- Commit signature verification for the [`builtins.fetchGit`](@docroot@/language/builtins.md#builtins-fetchGit) is added as the new [`verified-fetches` experimental feature](@docroot@/contributing/experimental-features.md#xp-feature-verified-fetches).
+
+- [`nix path-info --json`](@docroot@/command-ref/new-cli/nix3-path-info.md)
+  (experimental) now returns a JSON map rather than JSON list.
+  The `path` field of each object has instead become the key in the outer map, since it is unique.
+  The `valid` field also goes away because we just use `null` instead.
+
+  - Old way:
+
+    ```json5
+    [
+      {
+        "path": "/nix/store/8fv91097mbh5049i9rglc73dx6kjg3qk-bash-5.2-p15",
+        "valid": true,
+        // ...
+      },
+      {
+        "path": "/nix/store/wffw7l0alvs3iw94cbgi1gmmbmw99sqb-home-manager-path",
+        "valid": false
+      }
+    ]
+    ```
+
+  - New way
+
+    ```json5
+    {
+      "/nix/store/8fv91097mbh5049i9rglc73dx6kjg3qk-bash-5.2-p15": {
+        // ...
+      },
+      "/nix/store/wffw7l0alvs3iw94cbgi1gmmbmw99sqb-home-manager-path": null,
+    }
+    ```
+
+  This makes it match `nix derivation show`, which also maps store paths to information.
+
+- When Nix is installed using the [binary installer](@docroot@/installation/installing-binary.md), in supported shells (Bash, Zsh, Fish)
+  [`XDG_DATA_DIRS`](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html#variables) is now populated with the path to the `/share` subdirectory of the current profile.
+  This means that command completion scripts, `.desktop` files, and similar artifacts installed via [`nix-env`](@docroot@/command-ref/nix-env.md) or [`nix profile`](@docroot@/command-ref/new-cli/nix3-profile.md)
+  (experimental) can be found by any program that follows the [XDG Base Directory Specification](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html).
+
+- A new command `nix store add` has been added. It replaces `nix store add-file` and `nix store add-path` which are now deprecated.

doc/manual/src/store/file-system-object.md

@@ -0,0 +1,64 @@
+# File System Object
+
+Nix uses a simplified model of the file system, which consists of file system objects.
+Every file system object is one of the following:
+
+ - File
+
+   - A possibly empty sequence of bytes for contents
+   - A single boolean representing the [executable](https://en.m.wikipedia.org/wiki/File-system_permissions#Permissions) permission
+
+ - Directory
+
+   Mapping of names to child file system objects
+
+ - [Symbolic link](https://en.m.wikipedia.org/wiki/Symbolic_link)
+
+   An arbitrary string.
+   Nix does not assign any semantics to symbolic links.
+
+File system objects and their children form a tree.
+A bare file or symlink can be a root file system object.
+
+Nix does not encode any other file system notions such as [hard links](https://en.m.wikipedia.org/wiki/Hard_link), [permissions](https://en.m.wikipedia.org/wiki/File-system_permissions), timestamps, or other metadata.
+
+## Examples of file system objects
+
+A plain file:
+
+```
+50 B, executable: false
+```
+
+An executable file:
+
+```
+122 KB, executable: true
+```
+
+A symlink:
+
+```
+-> /usr/bin/sh
+```
+
+A directory with contents:
+
+```
+├── bin
+│   └── hello: 35 KB, executable: true
+└── share
+    ├── info
+    │   └── hello.info: 36 KB, executable: false
+    └── man
+        └── man1
+            └── hello.1.gz: 790 B, executable: false
+```
+
+A directory that contains a symlink and other directories:
+
+```
+├── bin -> share/go/bin
+├── nix-support/
+└── share/
+```

doc/manual/src/store/index.md

@@ -0,0 +1,5 @@
+# Nix Store
+
+The *Nix store* is an abstraction to store immutable file system data (such as software packages) that can have dependencies on other such data.
+
+There are multiple implementations of Nix stores with different capabilities, such as the actual filesystem (`/nix/store`) or binary caches.

doc/manual/src/store/store-object.md

@@ -0,0 +1,10 @@
+## Store Object
+
+A Nix store is a collection of *store objects* with *references* between them.
+A store object consists of
+
+  - A [file system object](./file-system-object.md) as data
+  - A set of [store paths](./store-path.md) as references to other store objects
+
+Store objects are [immutable](https://en.wikipedia.org/wiki/Immutable_object):
+Once created, they do not change until they are deleted.

doc/manual/src/store/store-path.md

@@ -0,0 +1,69 @@
+# Store Path
+
+Nix implements references to [store objects](./index.md#store-object) as *store paths*.
+
+Think of a store path as an [opaque], [unique identifier]:
+The only way to obtain store path is by adding or building store objects.
+A store path will always reference exactly one store object.
+
+[opaque]: https://en.m.wikipedia.org/wiki/Opaque_data_type
+[unique identifier]: https://en.m.wikipedia.org/wiki/Unique_identifier
+
+Store paths are pairs of
+
+- A 20-byte digest for identification
+- A symbolic name for people to read
+
+> **Example**
+>
+> - Digest: `b6gvzjyb2pg0kjfwrjmg1vfhh54ad73z`
+> - Name:   `firefox-33.1`
+
+To make store objects accessible to operating system processes, stores have to expose store objects through the file system.
+
+A store path is rendered to a file system path as the concatenation of
+
+- [Store directory](#store-directory) (typically `/nix/store`)
+- Path separator (`/`)
+- Digest rendered in a custom variant of [Base32](https://en.wikipedia.org/wiki/Base32) (20 arbitrary bytes become 32 ASCII characters)
+- Hyphen (`-`)
+- Name
+
+> **Example**
+>
+> ```
+>   /nix/store/b6gvzjyb2pg0kjfwrjmg1vfhh54ad73z-firefox-33.1
+>   |--------| |------------------------------| |----------|
+> store directory            digest                 name
+> ```
+
+## Store Directory
+
+Every [Nix store](./index.md) has a store directory.
+
+Not every store can be accessed through the file system.
+But if the store has a file system representation, the store directory contains the store’s [file system objects], which can be addressed by [store paths](#store-path).
+
+[file system objects]: ./file-system-object.md
+
+This means a store path is not just derived from the referenced store object itself, but depends on the store the store object is in.
+
+> **Note**
+>
+> The store directory defaults to `/nix/store`, but is in principle arbitrary.
+
+It is important which store a given store object belongs to:
+Files in the store object can contain store paths, and processes may read these paths.
+Nix can only guarantee referential integrity if store paths do not cross store boundaries.
+
+Therefore one can only copy store objects to a different store if
+
+- The source and target stores' directories match
+
+  or
+
+- The store object in question has no references, that is, contains no store paths
+
+One cannot copy a store object to a store with a different store directory.
+Instead, it has to be rebuilt, together with all its dependencies.
+It is in general not enough to replace the store directory string in file contents, as this may render executables unusable by invalidating their internal offsets or checksums.

doc/manual/utils.nix

@@ -44,63 +44,6 @@ rec {
 
   optionalString = cond: string: if cond then string else "";
 
-  showSetting = { useAnchors }: name: { description, documentDefault, defaultValue, aliases, value, experimentalFeature }:
-    let
-      result = squash ''
-          - ${if useAnchors
-              then ''<span id="conf-${name}">[`${name}`](#conf-${name})</span>''
-              else ''`${name}`''}
-
-          ${indent "  " body}
-        '';
-
-      experimentalFeatureNote = optionalString (experimentalFeature != null) ''
-          > **Warning**
-          > This setting is part of an
-          > [experimental feature](@docroot@/contributing/experimental-features.md).
-
-          To change this setting, you need to make sure the corresponding experimental feature,
-          [`${experimentalFeature}`](@docroot@/contributing/experimental-features.md#xp-feature-${experimentalFeature}),
-          is enabled.
-          For example, include the following in [`nix.conf`](#):
-
-          ```
-          extra-experimental-features = ${experimentalFeature}
-          ${name} = ...
-          ```
-        '';
-
-      # separate body to cleanly handle indentation
-      body = ''
-          ${description}
-
-          ${experimentalFeatureNote}
-
-          **Default:** ${showDefault documentDefault defaultValue}
-
-          ${showAliases aliases}
-        '';
-
-      showDefault = documentDefault: defaultValue:
-        if documentDefault then
-          # a StringMap value type is specified as a string, but
-          # this shows the value type. The empty stringmap is `null` in
-          # JSON, but that converts to `{ }` here.
-          if defaultValue == "" || defaultValue == [] || isAttrs defaultValue
-            then "*empty*"
-            else if isBool defaultValue then
-              if defaultValue then "`true`" else "`false`"
-            else "`${toString defaultValue}`"
-        else "*machine-specific*";
-
-      showAliases = aliases:
-          optionalString (aliases != [])
-            "**Deprecated alias:** ${(concatStringsSep ", " (map (s: "`${s}`") aliases))}";
-
-    in result;
-
   indent = prefix: s:
     concatStringsSep "\n" (map (x: if x == "" then x else "${prefix}${x}") (splitLines s));
-
-  showSettings = args: settingsInfo: concatStrings (attrValues (mapAttrs (showSetting args) settingsInfo));
 }

flake.lock

@@ -34,16 +34,16 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1670461440,
-        "narHash": "sha256-jy1LB8HOMKGJEGXgzFRLDU1CBGL0/LlkolgnqIsF0D8=",
+        "lastModified": 1698876495,
+        "narHash": "sha256-nsQo2/mkDUFeAjuu92p0dEqhRvHHiENhkKVIV1y0/Oo=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "04a75b2eecc0acf6239acf9dd04485ff8d14f425",
+        "rev": "9eb24edd6a0027fed010ccfe300a9734d029983c",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
-        "ref": "nixos-22.11-small",
+        "ref": "release-23.05",
         "repo": "nixpkgs",
         "type": "github"
       }

flake.nix

@@ -1,7 +1,9 @@
 {
   description = "The purely functional package manager";
 
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.11-small";
+  # FIXME go back to nixos-23.05-small once
+  # https://github.com/NixOS/nixpkgs/pull/264875 is included.
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/release-23.05";
   inputs.nixpkgs-regression.url = "github:NixOS/nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
   inputs.lowdown-src = { url = "github:kristapsdz/lowdown"; flake = false; };
   inputs.flake-compat = { url = "github:edolstra/flake-compat"; flake = false; };
@@ -11,7 +13,7 @@
     let
       inherit (nixpkgs) lib;
 
-      officialRelease = false;
+      officialRelease = true;
 
       version = lib.fileContents ./.version + versionSuffix;
       versionSuffix =
@@ -19,11 +21,16 @@
         then ""
         else "pre${builtins.substring 0 8 (self.lastModifiedDate or self.lastModified or "19700101")}_${self.shortRev or "dirty"}";
 
+      linux32BitSystems = [ "i686-linux" ];
       linux64BitSystems = [ "x86_64-linux" "aarch64-linux" ];
-      linuxSystems = linux64BitSystems ++ [ "i686-linux" ];
-      systems = linuxSystems ++ [ "x86_64-darwin" "aarch64-darwin" ];
+      linuxSystems = linux32BitSystems ++ linux64BitSystems;
+      darwinSystems = [ "x86_64-darwin" "aarch64-darwin" ];
+      systems = linuxSystems ++ darwinSystems;
 
-      crossSystems = [ "armv6l-linux" "armv7l-linux" ];
+      crossSystems = [
+        "armv6l-linux" "armv7l-linux"
+        "x86_64-freebsd13" "x86_64-netbsd"
+      ];
 
       stdenvs = [ "gccStdenv" "clangStdenv" "clang11Stdenv" "stdenv" "libcxxStdenv" "ccacheStdenv" ];
 
@@ -40,12 +47,69 @@
             })
             stdenvs);
 
+      # Experimental fileset library: https://github.com/NixOS/nixpkgs/pull/222981
+      # Not an "idiomatic" flake input because:
+      #  - Propagation to dependent locks: https://github.com/NixOS/nix/issues/7730
+      #  - Subflake would download redundant and huge parent flake
+      #  - No git tree hash support: https://github.com/NixOS/nix/issues/6044
+      inherit (import (builtins.fetchTarball { url = "https://github.com/NixOS/nix/archive/1bdcd7fc8a6a40b2e805bad759b36e64e911036b.tar.gz"; sha256 = "sha256:14ljlpdsp4x7h1fkhbmc4bd3vsqnx8zdql4h3037wh09ad6a0893"; }))
+        fileset;
+
+      baseFiles =
+        # .gitignore has already been processed, so any changes in it are irrelevant
+        # at this point. It is not represented verbatim for test purposes because
+        # that would interfere with repo semantics.
+        fileset.fileFilter (f: f.name != ".gitignore") ./.;
+
+      configureFiles = fileset.unions [
+        ./.version
+        ./configure.ac
+        ./m4
+        # TODO: do we really need README.md? It doesn't seem used in the build.
+        ./README.md
+      ];
+
+      topLevelBuildFiles = fileset.unions [
+        ./local.mk
+        ./Makefile
+        ./Makefile.config.in
+        ./mk
+      ];
+
+      functionalTestFiles = fileset.unions [
+        ./tests/functional
+        (fileset.fileFilter (f: lib.strings.hasPrefix "nix-profile" f.name) ./scripts)
+      ];
+
+      nixSrc = fileset.toSource {
+        root = ./.;
+        fileset = fileset.intersect baseFiles (fileset.unions [
+          configureFiles
+          topLevelBuildFiles
+          ./boehmgc-coroutine-sp-fallback.diff
+          ./doc
+          ./misc
+          ./precompiled-headers.h
+          ./src
+          ./unit-test-data
+          ./COPYING
+          ./scripts/local.mk
+          functionalTestFiles
+        ]);
+      };
 
       # Memoize nixpkgs for different platforms for efficiency.
       nixpkgsFor = forAllSystems
         (system: let
           make-pkgs = crossSystem: stdenv: import nixpkgs {
-            inherit system crossSystem;
+            localSystem = {
+              inherit system;
+            };
+            crossSystem = if crossSystem == null then null else {
+              system = crossSystem;
+            } // lib.optionalAttrs (crossSystem == "x86_64-freebsd13") {
+              useLLVM = true;
+            };
             overlays = [
               (overlayFor (p: p.${stdenv}))
             ];
@@ -100,6 +164,10 @@
 
         testConfigureFlags = [
           "RAPIDCHECK_HEADERS=${lib.getDev rapidcheck}/extras/gtest/include"
+        ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+          "--enable-install-unit-tests"
+          "--with-check-bin-dir=${builtins.placeholder "check"}/bin"
+          "--with-check-lib-dir=${builtins.placeholder "check"}/lib"
         ];
 
         internalApiDocsConfigureFlags = [
@@ -121,6 +189,7 @@
             buildPackages.git
             buildPackages.mercurial # FIXME: remove? only needed for tests
             buildPackages.jq # Also for custom mdBook preprocessor.
+            buildPackages.openssh # only needed for tests (ssh-keygen)
           ]
           ++ lib.optionals stdenv.hostPlatform.isLinux [(buildPackages.util-linuxMinimal or buildPackages.utillinuxMinimal)];
 
@@ -131,9 +200,9 @@
             libarchive
             boost
             lowdown-nix
+            libsodium
           ]
           ++ lib.optionals stdenv.isLinux [libseccomp]
-          ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium
           ++ lib.optional stdenv.hostPlatform.isx86_64 libcpuid;
 
         checkDeps = [
@@ -209,7 +278,14 @@
             "-${client.version}-against-${daemon.version}";
         inherit version;
 
-        src = self;
+        src = fileset.toSource {
+          root = ./.;
+          fileset = fileset.intersect baseFiles (fileset.unions [
+            configureFiles
+            topLevelBuildFiles
+            functionalTestFiles
+          ]);
+        };
 
         VERSION_SUFFIX = versionSuffix;
 
@@ -219,7 +295,9 @@
 
         enableParallelBuilding = true;
 
-        configureFlags = testConfigureFlags; # otherwise configure fails
+        configureFlags =
+          testConfigureFlags # otherwise configure fails
+          ++ [ "--disable-build" ];
         dontBuild = true;
         doInstallCheck = true;
 
@@ -227,7 +305,10 @@
           mkdir -p $out
         '';
 
-        installCheckPhase = "make installcheck -j$NIX_BUILD_CORES -l$NIX_BUILD_CORES";
+        installCheckPhase = ''
+          mkdir -p src/nix-channel
+          make installcheck -j$NIX_BUILD_CORES -l$NIX_BUILD_CORES
+        '';
       };
 
       binaryTarball = nix: pkgs:
@@ -320,21 +401,15 @@
           };
           let
             canRunInstalled = currentStdenv.buildPlatform.canExecute currentStdenv.hostPlatform;
-
-            sourceByRegexInverted = rxs: origSrc: final.lib.cleanSourceWith {
-              filter = (path: type:
-                let relPath = final.lib.removePrefix (toString origSrc + "/") (toString path);
-                in ! lib.any (re: builtins.match re relPath != null) rxs);
-              src = origSrc;
-            };
           in currentStdenv.mkDerivation (finalAttrs: {
             name = "nix-${version}";
             inherit version;
 
-            src = sourceByRegexInverted [ "tests/nixos/.*" "tests/installer/.*" ] self;
+            src = nixSrc;
             VERSION_SUFFIX = versionSuffix;
 
-            outputs = [ "out" "dev" "doc" ];
+            outputs = [ "out" "dev" "doc" ]
+              ++ lib.optional (currentStdenv.hostPlatform != currentStdenv.buildPlatform) "check";
 
             nativeBuildInputs = nativeBuildDeps;
             buildInputs = buildDeps
@@ -407,39 +482,13 @@
 
             hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
 
-            passthru.perl-bindings = with final; perl.pkgs.toPerlModule (currentStdenv.mkDerivation {
-              name = "nix-perl-${version}";
-
-              src = self;
-
-              nativeBuildInputs =
-                [ buildPackages.autoconf-archive
-                  buildPackages.autoreconfHook
-                  buildPackages.pkg-config
-                ];
-
-              buildInputs =
-                [ nix
-                  curl
-                  bzip2
-                  xz
-                  pkgs.perl
-                  boost
-                ]
-                ++ lib.optional (currentStdenv.isLinux || currentStdenv.isDarwin) libsodium
-                ++ lib.optional currentStdenv.isDarwin darwin.apple_sdk.frameworks.Security;
-
-              configureFlags = [
-                "--with-dbi=${perlPackages.DBI}/${pkgs.perl.libPrefix}"
-                "--with-dbd-sqlite=${perlPackages.DBDSQLite}/${pkgs.perl.libPrefix}"
-              ];
-
-              enableParallelBuilding = true;
-
-              postUnpack = "sourceRoot=$sourceRoot/perl";
-            });
+            passthru.perl-bindings = final.callPackage ./perl {
+              inherit fileset;
+              stdenv = currentStdenv;
+            };
 
             meta.platforms = lib.platforms.unix;
+            meta.mainProgram = "nix";
           });
 
           lowdown-nix = with final; currentStdenv.mkDerivation rec {
@@ -460,18 +509,6 @@
           };
         };
 
-      nixos-lib = import (nixpkgs + "/nixos/lib") { };
-
-      # https://nixos.org/manual/nixos/unstable/index.html#sec-calling-nixos-tests
-      runNixOSTestFor = system: test: nixos-lib.runTest {
-        imports = [ test ];
-        hostPkgs = nixpkgsFor.${system}.native;
-        defaults = {
-          nixpkgs.pkgs = nixpkgsFor.${system}.native;
-        };
-        _module.args.nixpkgs = nixpkgs;
-      };
-
     in {
       # A Nixpkgs overlay that overrides the 'nix' and
       # 'nix.perl-bindings' packages.
@@ -529,7 +566,7 @@
           releaseTools.coverageAnalysis {
             name = "nix-coverage-${version}";
 
-            src = self;
+            src = nixSrc;
 
             configureFlags = testConfigureFlags;
 
@@ -546,6 +583,8 @@
             lcovFilter = [ "*/boost/*" "*-tab.*" ];
 
             hardeningDisable = ["fortify"];
+
+            NIX_CFLAGS_COMPILE = "-DCOVERAGE=1";
           };
 
         # API docs for Nix's unstable internal C++ interfaces.
@@ -557,7 +596,7 @@
             pname = "nix-internal-api-docs";
             inherit version;
 
-            src = self;
+            src = nixSrc;
 
             configureFlags = testConfigureFlags ++ internalApiDocsConfigureFlags;
 
@@ -576,45 +615,29 @@
           };
 
         # System tests.
-        tests.authorization = runNixOSTestFor "x86_64-linux" ./tests/nixos/authorization.nix;
+        tests = import ./tests/nixos { inherit lib nixpkgs nixpkgsFor; } // {
 
-        tests.remoteBuilds = runNixOSTestFor "x86_64-linux" ./tests/nixos/remote-builds.nix;
+          # Make sure that nix-env still produces the exact same result
+          # on a particular version of Nixpkgs.
+          evalNixpkgs =
+            with nixpkgsFor.x86_64-linux.native;
+            runCommand "eval-nixos" { buildInputs = [ nix ]; }
+              ''
+                type -p nix-env
+                # Note: we're filtering out nixos-install-tools because https://github.com/NixOS/nixpkgs/pull/153594#issuecomment-1020530593.
+                time nix-env --store dummy:// -f ${nixpkgs-regression} -qaP --drv-path | sort | grep -v nixos-install-tools > packages
+                [[ $(sha1sum < packages | cut -c1-40) = ff451c521e61e4fe72bdbe2d0ca5d1809affa733 ]]
+                mkdir $out
+              '';
 
-        tests.nix-copy-closure = runNixOSTestFor "x86_64-linux" ./tests/nixos/nix-copy-closure.nix;
-
-        tests.nix-copy = runNixOSTestFor "x86_64-linux" ./tests/nixos/nix-copy.nix;
-
-        tests.nssPreload = runNixOSTestFor "x86_64-linux" ./tests/nixos/nss-preload.nix;
-
-        tests.githubFlakes = runNixOSTestFor "x86_64-linux" ./tests/nixos/github-flakes.nix;
-
-        tests.sourcehutFlakes = runNixOSTestFor "x86_64-linux" ./tests/nixos/sourcehut-flakes.nix;
-
-        tests.containers = runNixOSTestFor "x86_64-linux" ./tests/nixos/containers/containers.nix;
-
-        tests.setuid = lib.genAttrs
-          ["i686-linux" "x86_64-linux"]
-          (system: runNixOSTestFor system ./tests/nixos/setuid.nix);
-
-
-        # Make sure that nix-env still produces the exact same result
-        # on a particular version of Nixpkgs.
-        tests.evalNixpkgs =
-          with nixpkgsFor.x86_64-linux.native;
-          runCommand "eval-nixos" { buildInputs = [ nix ]; }
-            ''
-              type -p nix-env
-              # Note: we're filtering out nixos-install-tools because https://github.com/NixOS/nixpkgs/pull/153594#issuecomment-1020530593.
-              time nix-env --store dummy:// -f ${nixpkgs-regression} -qaP --drv-path | sort | grep -v nixos-install-tools > packages
-              [[ $(sha1sum < packages | cut -c1-40) = ff451c521e61e4fe72bdbe2d0ca5d1809affa733 ]]
-              mkdir $out
-            '';
-
-        tests.nixpkgsLibTests =
-          forAllSystems (system:
-            import (nixpkgs + "/lib/tests/release.nix")
-              { pkgs = nixpkgsFor.${system}.native; }
-          );
+          nixpkgsLibTests =
+            forAllSystems (system:
+              import (nixpkgs + "/lib/tests/release.nix")
+                { pkgs = nixpkgsFor.${system}.native;
+                  nixVersions = [ self.packages.${system}.nix ];
+                }
+            );
+        };
 
         metrics.nixpkgs = import "${nixpkgs-regression}/pkgs/top-level/metrics.nix" {
           pkgs = nixpkgsFor.x86_64-linux.native;
@@ -685,20 +708,29 @@
 
       devShells = let
         makeShell = pkgs: stdenv:
+          let
+            canRunInstalled = stdenv.buildPlatform.canExecute stdenv.hostPlatform;
+          in
           with commonDeps { inherit pkgs; };
           stdenv.mkDerivation {
             name = "nix";
 
-            outputs = [ "out" "dev" "doc" ];
+            outputs = [ "out" "dev" "doc" ]
+              ++ lib.optional (stdenv.hostPlatform != stdenv.buildPlatform) "check";
 
             nativeBuildInputs = nativeBuildDeps
-                                ++ (lib.optionals stdenv.cc.isClang [ pkgs.bear pkgs.clang-tools ]);
+              ++ lib.optional stdenv.cc.isClang pkgs.buildPackages.bear
+              ++ lib.optional
+                (stdenv.cc.isClang && stdenv.hostPlatform == stdenv.buildPlatform)
+                pkgs.buildPackages.clang-tools
+              ;
 
             buildInputs = buildDeps ++ propagatedDeps
               ++ awsDeps ++ checkDeps ++ internalApiDocsDeps;
 
             configureFlags = configureFlags
-              ++ testConfigureFlags ++ internalApiDocsConfigureFlags;
+              ++ testConfigureFlags ++ internalApiDocsConfigureFlags
+              ++ lib.optional (!canRunInstalled) "--disable-doc-gen";
 
             enableParallelBuilding = true;
 

local.mk

@@ -1,5 +1,3 @@
-clean-files += Makefile.config
-
 GLOBAL_CXXFLAGS += -Wno-deprecated-declarations -Werror=switch
 # Allow switch-enum to be overridden for files that do not support it, usually because of dependency headers.
 ERROR_SWITCH_ENUM = -Werror=switch-enum

m4/gcc_bug_80431.m4

@@ -0,0 +1,64 @@
+# Ensure that this bug is not present in the C++ toolchain we are using.
+#
+# URL for bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80431
+#
+# The test program is from that issue, with only a slight modification
+# to set an exit status instead of printing strings.
+AC_DEFUN([ENSURE_NO_GCC_BUG_80431],
+[
+  AC_MSG_CHECKING([that GCC bug 80431 is fixed])
+  AC_LANG_PUSH(C++)
+  AC_RUN_IFELSE(
+    [AC_LANG_PROGRAM(
+      [[
+        #include <cstdio>
+
+        static bool a = true;
+        static bool b = true;
+
+        struct Options { };
+
+        struct Option
+        {
+            Option(Options * options)
+            {
+                a = false;
+            }
+
+            ~Option()
+            {
+                b = false;
+            }
+        };
+
+        struct MyOptions : Options { };
+
+        struct MyOptions2 : virtual MyOptions
+        {
+            Option foo{this};
+        };
+      ]],
+      [[
+        {
+            MyOptions2 opts;
+        }
+        return (a << 1) | b;
+      ]])],
+    [status_80431=0],
+    [status_80431=$?],
+    [
+      # Assume we're bug-free when cross-compiling
+    ])
+  AC_LANG_POP(C++)
+  AS_CASE([$status_80431],
+    [0],[
+      AC_MSG_RESULT(yes)
+    ],
+    [2],[
+      AC_MSG_RESULT(no)
+      AC_MSG_ERROR(Cannot build Nix with C++ compiler with this bug)
+    ],
+    [
+      AC_MSG_RESULT(unexpected result $status_80431: not expected failure with bug, ignoring)
+    ])
+])

maintainers/README.md

@@ -2,7 +2,7 @@
 
 ## Motivation
 
-The team's main responsibility is to set a direction for the development of Nix and ensure that the code is in good shape.
+The team's main responsibility is to guide and direct the development of Nix and ensure that the code is in good shape.
 
 We aim to achieve this by improving the contributor experience and attracting more maintainers – that is, by helping other people contributing to Nix and eventually taking responsibility – in order to scale the development process to match users' needs.
 
@@ -50,7 +50,9 @@ The team meets twice a week:
   1. Code review on pull requests from [In review](#in-review).
   2. Other chores and tasks.
 
-Meeting notes are collected on a [collaborative scratchpad](https://pad.lassul.us/Cv7FpYx-Ri-4VjUykQOLAw), and published on Discourse under the [Nix category](https://discourse.nixos.org/c/dev/nix/50).
+Meeting notes are collected on a [collaborative scratchpad](https://pad.lassul.us/Cv7FpYx-Ri-4VjUykQOLAw).
+Notes on issues and pull requests are posted as comments and linked from the meeting notes, so they are easy to find from both places.
+[All meeting notes](https://discourse.nixos.org/search?expanded=true&q=Nix%20team%20meeting%20minutes%20%23%20%23dev%3Anix%20in%3Atitle%20order%3Alatest_topic) are published on Discourse under the [Nix category](https://discourse.nixos.org/c/dev/nix/50).
 
 ## Project board protocol
 
@@ -96,8 +98,10 @@ What constitutes a trivial pull request is up to maintainers' judgement.
 Pull requests and issues that are deemed important and controversial are discussed by the team during discussion meetings.
 
 This may be where the merit of the change itself or the implementation strategy is contested by a team member.
+Whenever the discussion opens up questions about the process or this team's goals, this may indicate that the change is too large in scope.
+In that case it is taken off the board to be reconsidered by the author or broken down into smaller pieces that are less far-reaching and can be reviewed independently.
 
-As a general guideline, the order of items is determined as follows:
+As a general guideline, the order of items to discuss is determined as follows:
 
 - Prioritise pull requests over issues
 
@@ -117,6 +121,7 @@ Pull requests in this column are reviewed together during work meetings.
 This is both for spreading implementation knowledge and for establishing common values in code reviews.
 
 When the overall direction is agreed upon, even when further changes are required, the pull request is assigned to one team member.
+If significant changes are requested or reviewers cannot come to a conclusion in reasonable time, the pull request is [marked as draft](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/changing-the-stage-of-a-pull-request#converting-a-pull-request-to-a-draft).
 
 ### Assigned
 

maintainers/release-process.md

@@ -119,8 +119,7 @@ release:
   TODO: This script requires the right AWS credentials. Document.
 
   TODO: This script currently requires a
-  `/home/eelco/Dev/nix-pristine` and
-  `/home/eelco/Dev/nixpkgs-pristine`.
+  `/home/eelco/Dev/nix-pristine`.
 
   TODO: trigger nixos.org netlify: https://docs.netlify.com/configure-builds/build-hooks/
 
@@ -141,7 +140,7 @@ release:
   $ git checkout master
   $ git pull
   $ NEW_VERSION=2.13.0
-  $ echo -n $NEW_VERSION > .version
+  $ echo $NEW_VERSION > .version
   $ git checkout -b bump-$NEW_VERSION
   $ git commit -a -m 'Bump version'
   $ git push --set-upstream origin bump-$NEW_VERSION

maintainers/upload-release.pl

@@ -80,6 +80,38 @@ my $s3_us = Net::Amazon::S3->new(
 
 my $channelsBucket = $s3_us->bucket($channelsBucketName) or die;
 
+sub getStorePath {
+    my ($jobName, $output) = @_;
+    my $buildInfo = decode_json(fetch("$evalUrl/job/$jobName", 'application/json'));
+    return $buildInfo->{buildoutputs}->{$output or "out"}->{path} or die "cannot get store path for '$jobName'";
+}
+
+sub copyManual {
+    my $manual = getStorePath("build.x86_64-linux", "doc");
+    print "$manual\n";
+
+    my $manualNar = "$tmpDir/$releaseName-manual.nar.xz";
+    print "$manualNar\n";
+
+    unless (-e $manualNar) {
+        system("NIX_REMOTE=$binaryCache nix store dump-path '$manual' | xz > '$manualNar'.tmp") == 0
+            or die "unable to fetch $manual\n";
+        rename("$manualNar.tmp", $manualNar) or die;
+    }
+
+    unless (-e "$tmpDir/manual") {
+        system("xz -d < '$manualNar' | nix-store --restore $tmpDir/manual.tmp") == 0
+            or die "unable to unpack $manualNar\n";
+        rename("$tmpDir/manual.tmp/share/doc/nix/manual", "$tmpDir/manual") or die;
+        system("rm -rf '$tmpDir/manual.tmp'") == 0 or die;
+    }
+
+    system("aws s3 sync '$tmpDir/manual' s3://$releasesBucketName/$releaseDir/manual") == 0
+        or die "syncing manual to S3\n";
+}
+
+copyManual;
+
 sub downloadFile {
     my ($jobName, $productNr, $dstName) = @_;
 
@@ -179,9 +211,20 @@ if ($isLatest) {
     system("docker manifest push nixos/nix:latest") == 0 or die;
 }
 
+# Upload nix-fallback-paths.nix.
+write_file("$tmpDir/fallback-paths.nix",
+    "{\n" .
+    "  x86_64-linux = \"" . getStorePath("build.x86_64-linux") . "\";\n" .
+    "  i686-linux = \"" . getStorePath("build.i686-linux") . "\";\n" .
+    "  aarch64-linux = \"" . getStorePath("build.aarch64-linux") . "\";\n" .
+    "  x86_64-darwin = \"" . getStorePath("build.x86_64-darwin") . "\";\n" .
+    "  aarch64-darwin = \"" . getStorePath("build.aarch64-darwin") . "\";\n" .
+    "}\n");
+
 # Upload release files to S3.
 for my $fn (glob "$tmpDir/*") {
     my $name = basename($fn);
+    next if $name eq "manual";
     my $dstKey = "$releaseDir/" . $name;
     unless (defined $releasesBucket->head_key($dstKey)) {
         print STDERR "uploading $fn to s3://$releasesBucketName/$dstKey...\n";
@@ -189,8 +232,7 @@ for my $fn (glob "$tmpDir/*") {
         my $configuration = ();
         $configuration->{content_type} = "application/octet-stream";
 
-        if ($fn =~ /.sha256|install/) {
-            # Text files
+        if ($fn =~ /.sha256|install|\.nix$/) {
             $configuration->{content_type} = "text/plain";
         }
 
@@ -199,24 +241,6 @@ for my $fn (glob "$tmpDir/*") {
     }
 }
 
-# Print new nix-fallback-paths.nix.
-if ($isLatest) {
-    sub getStorePath {
-        my ($jobName) = @_;
-        my $buildInfo = decode_json(fetch("$evalUrl/job/$jobName", 'application/json'));
-        return $buildInfo->{buildoutputs}->{out}->{path} or die "cannot get store path for '$jobName'";
-    }
-
-    print STDERR "nixos/modules/installer/tools/nix-fallback-paths.nix:\n" .
-               "{\n" .
-               "  x86_64-linux = \"" . getStorePath("build.x86_64-linux") . "\";\n" .
-               "  i686-linux = \"" . getStorePath("build.i686-linux") . "\";\n" .
-               "  aarch64-linux = \"" . getStorePath("build.aarch64-linux") . "\";\n" .
-               "  x86_64-darwin = \"" . getStorePath("build.x86_64-darwin") . "\";\n" .
-               "  aarch64-darwin = \"" . getStorePath("build.aarch64-darwin") . "\";\n" .
-               "}\n";
-}
-
 # Update the "latest" symlink.
 $channelsBucket->add_key(
     "nix-latest/install", "",

misc/systemd/nix-daemon.service.in

@@ -10,6 +10,7 @@ ConditionPathIsReadWrite=@localstatedir@/nix/daemon-socket
 ExecStart=@@bindir@/nix-daemon nix-daemon --daemon
 KillMode=process
 LimitNOFILE=1048576
+TasksMax=1048576
 
 [Install]
 WantedBy=multi-user.target

mk/common-test.sh

@@ -1,11 +1,27 @@
-TESTS_ENVIRONMENT=("TEST_NAME=${test%.*}" 'NIX_REMOTE=')
+# Remove overall test dir (at most one of the two should match) and
+# remove file extension.
+test_name=$(echo -n "$test" | sed \
+    -e "s|^unit-test-data/||" \
+    -e "s|^tests/functional/||" \
+    -e "s|\.sh$||" \
+    )
+
+TESTS_ENVIRONMENT=(
+    "TEST_NAME=$test_name"
+    'NIX_REMOTE='
+    'PS4=+(${BASH_SOURCE[0]-$0}:$LINENO) '
+)
 
 : ${BASH:=/usr/bin/env bash}
 
+run () {
+   cd "$(dirname $1)" && env "${TESTS_ENVIRONMENT[@]}" $BASH -x -e -u -o pipefail $(basename $1)
+}
+
 init_test () {
-   cd tests && env "${TESTS_ENVIRONMENT[@]}" $BASH -e init.sh 2>/dev/null > /dev/null
+   run "$init" 2>/dev/null > /dev/null
 }
 
 run_test_proper () {
-   cd $(dirname $test) && env "${TESTS_ENVIRONMENT[@]}" $BASH -e $(basename $test)
+   run "$test"
 }

mk/debug-test.sh

@@ -3,9 +3,12 @@
 set -eu -o pipefail
 
 test=$1
+init=${2-}
 
 dir="$(dirname "${BASH_SOURCE[0]}")"
 source "$dir/common-test.sh"
 
-(init_test)
+if [ -n "$init" ]; then
+    (init_test)
+fi
 run_test_proper

mk/lib.mk

@@ -10,6 +10,7 @@ bin-scripts :=
 noinst-scripts :=
 man-pages :=
 install-tests :=
+install-tests-groups :=
 
 ifdef HOST_OS
   HOST_KERNEL = $(firstword $(subst -, ,$(HOST_OS)))
@@ -121,7 +122,17 @@ $(foreach script, $(bin-scripts), $(eval $(call install-program-in,$(script),$(b
 $(foreach script, $(bin-scripts), $(eval programs-list += $(script)))
 $(foreach script, $(noinst-scripts), $(eval programs-list += $(script)))
 $(foreach template, $(template-files), $(eval $(call instantiate-template,$(template))))
-$(foreach test, $(install-tests), $(eval $(call run-install-test,$(test))))
+install_test_init=tests/functional/init.sh
+$(foreach test, $(install-tests), \
+  $(eval $(call run-test,$(test),$(install_test_init))) \
+  $(eval installcheck: $(test).test))
+$(foreach test-group, $(install-tests-groups), \
+  $(eval $(call run-test-group,$(test-group),$(install_test_init))) \
+  $(eval installcheck: $(test-group).test-group) \
+  $(foreach test, $($(test-group)-tests), \
+    $(eval $(call run-test,$(test),$(install_test_init))) \
+    $(eval $(test-group).test-group: $(test).test)))
+
 $(foreach file, $(man-pages), $(eval $(call install-data-in, $(file), $(mandir)/man$(patsubst .%,%,$(suffix $(file))))))
 
 
@@ -151,6 +162,14 @@ ifdef libs-list
 	@echo "The following libraries can be built:"
 	@echo ""
 	@for i in $(libs-list); do echo "  $$i"; done
+endif
+ifdef install-tests-groups
+	@echo ""
+	@echo "The following groups of functional tests can be run:"
+	@echo ""
+	@for i in $(install-tests-groups); do echo "  $$i.test-group"; done
+	@echo ""
+	@echo "(installcheck includes tests in test groups too.)"
 endif
 	@echo ""
 	@echo "The following variables control the build:"

mk/programs.mk

@@ -87,6 +87,6 @@ define build-program
   # Phony target to run this program (typically as a dependency of 'check').
   .PHONY: $(1)_RUN
   $(1)_RUN: $$($(1)_PATH)
-	$(trace-test) $$($(1)_PATH)
+	$(trace-test) $$(UNIT_TEST_ENV) $$($(1)_PATH)
 
 endef

mk/run-test.sh

@@ -8,6 +8,7 @@ yellow=""
 normal=""
 
 test=$1
+init=${2-}
 
 dir="$(dirname "${BASH_SOURCE[0]}")"
 source "$dir/common-test.sh"
@@ -21,7 +22,9 @@ if [ -t 1 ]; then
 fi
 
 run_test () {
-    (init_test 2>/dev/null > /dev/null)
+    if [ -n "$init" ]; then
+        (init_test 2>/dev/null > /dev/null)
+    fi
     log="$(run_test_proper 2>&1)" && status=0 || status=$?
 }
 

mk/tests.mk

@@ -2,17 +2,24 @@
 
 test-deps =
 
-define run-install-test
+define run-bash
 
-  installcheck: $1.test
+  .PHONY: $1
+  $1: $2
+	@env BASH=$(bash) $(bash) $3 < /dev/null
 
-  .PHONY: $1.test
-  $1.test: $1 $(test-deps)
-	@env BASH=$(bash) $(bash) mk/run-test.sh $1 < /dev/null
+endef
 
-  .PHONY: $1.test-debug
-  $1.test-debug: $1 $(test-deps)
-	@env BASH=$(bash) $(bash) mk/debug-test.sh $1 < /dev/null
+define run-test
+
+  $(eval $(call run-bash,$1.test,$1 $(test-deps),mk/run-test.sh $1 $2))
+  $(eval $(call run-bash,$1.test-debug,$1 $(test-deps),mk/debug-test.sh $1 $2))
+
+endef
+
+define run-test-group
+
+  .PHONY: $1.test-group
 
 endef
 

perl/Makefile

@@ -1,6 +1,12 @@
 makefiles = local.mk
 
-GLOBAL_CXXFLAGS += -g -Wall -std=c++2a -I ../src
+GLOBAL_CXXFLAGS += -g -Wall -std=c++2a
+
+# A convenience for concurrent development of Nix and its Perl bindings.
+# Not needed in a standalone build of the Perl bindings.
+ifneq ("$(wildcard ../src)", "")
+  GLOBAL_CXXFLAGS += -I ../src
+endif
 
 -include Makefile.config
 

perl/default.nix

@@ -0,0 +1,51 @@
+{ lib, fileset
+, stdenv
+, perl, perlPackages
+, autoconf-archive, autoreconfHook, pkg-config
+, nix, curl, bzip2, xz, boost, libsodium, darwin
+}:
+
+perl.pkgs.toPerlModule (stdenv.mkDerivation {
+  name = "nix-perl-${nix.version}";
+
+  src = fileset.toSource {
+    root = ../.;
+    fileset = fileset.unions [
+      ../.version
+      ../m4
+      ../mk
+      ./MANIFEST
+      ./Makefile
+      ./Makefile.config.in
+      ./configure.ac
+      ./lib
+      ./local.mk
+    ];
+  };
+
+  nativeBuildInputs =
+    [ autoconf-archive
+      autoreconfHook
+      pkg-config
+    ];
+
+  buildInputs =
+    [ nix
+      curl
+      bzip2
+      xz
+      perl
+      boost
+    ]
+    ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium
+    ++ lib.optional stdenv.isDarwin darwin.apple_sdk.frameworks.Security;
+
+  configureFlags = [
+    "--with-dbi=${perlPackages.DBI}/${perl.libPrefix}"
+    "--with-dbd-sqlite=${perlPackages.DBDSQLite}/${perl.libPrefix}"
+  ];
+
+  enableParallelBuilding = true;
+
+  postUnpack = "sourceRoot=$sourceRoot/perl";
+})

perl/lib/Nix/Store.xs

@@ -11,7 +11,6 @@
 #include "derivations.hh"
 #include "globals.hh"
 #include "store-api.hh"
-#include "util.hh"
 #include "crypto.hh"
 
 #include <sodium.h>
@@ -78,7 +77,7 @@ SV * queryReferences(char * path)
 SV * queryPathHash(char * path)
     PPCODE:
         try {
-            auto s = store()->queryPathInfo(store()->parseStorePath(path))->narHash.to_string(Base32, true);
+            auto s = store()->queryPathInfo(store()->parseStorePath(path))->narHash.to_string(HashFormat::Base32, true);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -104,7 +103,7 @@ SV * queryPathInfo(char * path, int base32)
                 XPUSHs(&PL_sv_undef);
             else
                 XPUSHs(sv_2mortal(newSVpv(store()->printStorePath(*info->deriver).c_str(), 0)));
-            auto s = info->narHash.to_string(base32 ? Base32 : Base16, true);
+            auto s = info->narHash.to_string(base32 ? HashFormat::Base32 : HashFormat::Base16, true);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
             mXPUSHi(info->registrationTime);
             mXPUSHi(info->narSize);
@@ -206,7 +205,7 @@ SV * hashPath(char * algo, int base32, char * path)
     PPCODE:
         try {
             Hash h = hashPath(parseHashType(algo), path).first;
-            auto s = h.to_string(base32 ? Base32 : Base16, false);
+            auto s = h.to_string(base32 ? HashFormat::Base32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -217,7 +216,7 @@ SV * hashFile(char * algo, int base32, char * path)
     PPCODE:
         try {
             Hash h = hashFile(parseHashType(algo), path);
-            auto s = h.to_string(base32 ? Base32 : Base16, false);
+            auto s = h.to_string(base32 ? HashFormat::Base32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -228,7 +227,7 @@ SV * hashString(char * algo, int base32, char * s)
     PPCODE:
         try {
             Hash h = hashString(parseHashType(algo), s);
-            auto s = h.to_string(base32 ? Base32 : Base16, false);
+            auto s = h.to_string(base32 ? HashFormat::Base32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -239,7 +238,7 @@ SV * convertHash(char * algo, char * s, int toBase32)
     PPCODE:
         try {
             auto h = Hash::parseAny(s, parseHashType(algo));
-            auto s = h.to_string(toBase32 ? Base32 : Base16, false);
+            auto s = h.to_string(toBase32 ? HashFormat::Base32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -294,10 +293,8 @@ SV * makeFixedOutputPath(int recursive, char * algo, char * hash, char * name)
             auto h = Hash::parseAny(hash, parseHashType(algo));
             auto method = recursive ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat;
             auto path = store()->makeFixedOutputPath(name, FixedOutputInfo {
-                .hash = {
-                    .method = method,
-                    .hash = h,
-                },
+                .method = method,
+                .hash = h,
                 .references = {},
             });
             XPUSHs(sv_2mortal(newSVpv(store()->printStorePath(path).c_str(), 0)));
@@ -326,7 +323,7 @@ SV * derivationFromPath(char * drvPath)
             hv_stores(hash, "outputs", newRV((SV *) outputs));
 
             AV * inputDrvs = newAV();
-            for (auto & i : drv.inputDrvs)
+            for (auto & i : drv.inputDrvs.map)
                 av_push(inputDrvs, newSVpv(store()->printStorePath(i.first).c_str(), 0)); // !!! ignores i->second
             hv_stores(hash, "inputDrvs", newRV((SV *) inputDrvs));