Merge pull request #7694 from NixOS/backport-7685-to-2.13-maintenance

[Backport 2.13-maintenance] Fix the 2.13 changelog

.github/CODEOWNERS

@@ -0,0 +1,15 @@
+# Pull requests concerning the listed files will automatically invite the respective maintainers as reviewers.
+# This file is not used for denoting any kind of ownership, but is merely a tool for handling notifications.
+#
+# Merge permissions are required for maintaining an entry in this file.
+# For documentation on this mechanism, see https://help.github.com/articles/about-codeowners/
+
+# Default reviewers if nothing else matches
+* @edolstra @thufschmitt
+
+# This file
+.github/CODEOWNERS @edolstra
+
+# Public documentation
+/doc @fricklerhandwerk
+*.md @fricklerhandwerk

.github/ISSUE_TEMPLATE/bug_report.md

@@ -30,3 +30,7 @@ A clear and concise description of what you expected to happen.
 **Additional context**
 
 Add any other context about the problem here.
+
+**Priorities**
+
+Add :+1: to [issues you find important](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc).

.github/ISSUE_TEMPLATE/feature_request.md

@@ -18,3 +18,7 @@ A clear and concise description of any alternative solutions or features you've
 
 **Additional context**
 Add any other context or screenshots about the feature request here.
+
+**Priorities**
+
+Add :+1: to [issues you find important](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc).

.github/ISSUE_TEMPLATE/installer.md

@@ -0,0 +1,36 @@
+---
+name: Installer issue
+about: Report problems with installation
+title: ''
+labels: installer
+assignees: ''
+
+---
+
+## Platform
+
+<!-- select the platform on which you tried to install Nix -->
+
+- [ ] Linux: <!-- state your distribution, e.g. Arch Linux, Ubuntu, ... -->
+- [ ] macOS
+- [ ] WSL
+
+## Additional information
+
+<!-- state special circumstances on your system or additional steps you have taken prior to installation -->
+
+## Output
+
+<details><summary>Output</summary>
+
+```log
+
+<!-- paste console output here and remove this comment -->
+
+```
+
+</details>
+
+## Priorities
+
+Add :+1: to [issues you find important](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc).

.github/ISSUE_TEMPLATE/missing_documentation.md

@@ -26,3 +26,6 @@ assignees: ''
 
 <!-- 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/pull_request_template.md

@@ -5,3 +5,7 @@ Please include relevant [release notes](https://github.com/NixOS/nix/blob/master
 **Testing**
 
 If this issue is a regression or something that should block release, please consider including a test either in the [testsuite](https://github.com/NixOS/nix/tree/master/tests) or as a [hydraJob]( https://github.com/NixOS/nix/blob/master/flake.nix#L396) so that it can be part of the [automatic checks](https://hydra.nixos.org/jobset/nix/master).
+
+**Priorities**
+
+Add :+1: to [pull requests you find important](https://github.com/NixOS/nix/pulls?q=is%3Aopen+sort%3Areactions-%2B1-desc).

.github/workflows/backport.yml

@@ -21,7 +21,7 @@ jobs:
           fetch-depth: 0
       - name: Create backport PRs
         # should be kept in sync with `version`
-        uses: zeebe-io/backport-action@v0.0.8
+        uses: zeebe-io/backport-action@v1.0.1
         with:
           # Config README: https://github.com/zeebe-io/backport-action#backport-action
           github_token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/ci.yml

@@ -19,9 +19,9 @@ jobs:
     - uses: actions/checkout@v3
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v17
+    - uses: cachix/install-nix-action@v18
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/cachix-action@v10
+    - uses: cachix/cachix-action@v12
       if: needs.check_secrets.outputs.cachix == 'true'
       with:
         name: '${{ env.CACHIX_NAME }}'
@@ -58,8 +58,8 @@ jobs:
       with:
         fetch-depth: 0
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v17
-    - uses: cachix/cachix-action@v10
+    - uses: cachix/install-nix-action@v18
+    - uses: cachix/cachix-action@v12
       with:
         name: '${{ env.CACHIX_NAME }}'
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
@@ -77,7 +77,7 @@ jobs:
     steps:
     - uses: actions/checkout@v3
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v17
+    - uses: cachix/install-nix-action@v18
       with:
         install_url: '${{needs.installer.outputs.installerURL}}'
         install_options: "--tarball-url-prefix https://${{ env.CACHIX_NAME }}.cachix.org/serve"
@@ -102,10 +102,10 @@ jobs:
     - uses: actions/checkout@v3
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v17
+    - uses: cachix/install-nix-action@v18
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
     - run: echo NIX_VERSION="$(nix --experimental-features 'nix-command flakes' eval .\#default.version | tr -d \")" >> $GITHUB_ENV
-    - uses: cachix/cachix-action@v10
+    - uses: cachix/cachix-action@v12
       if: needs.check_secrets.outputs.cachix == 'true'
       with:
         name: '${{ env.CACHIX_NAME }}'

.version

@@ -1 +1 @@
-2.12.0
+2.13.2

boehmgc-coroutine-sp-fallback.diff

@@ -31,19 +31,19 @@ index 3dbaa3fb..36a1d1f7 100644
              GC_push_all_stack(altstack_lo, altstack_hi);
            }
 diff --git a/pthread_stop_world.c b/pthread_stop_world.c
-index 4b2c429..1fb4c52 100644
+index b5d71e62..aed7b0bf 100644
 --- a/pthread_stop_world.c
 +++ b/pthread_stop_world.c
-@@ -673,6 +673,8 @@ GC_INNER void GC_push_all_stacks(void)
-     struct GC_traced_stack_sect_s *traced_stack_sect;
-     pthread_t self = pthread_self();
-     word total_size = 0;
+@@ -768,6 +768,8 @@ STATIC void GC_restart_handler(int sig)
+ /* world is stopped.  Should not fail if it isn't.                      */
+ GC_INNER void GC_push_all_stacks(void)
+ {
 +    size_t stack_limit;
 +    pthread_attr_t pattr;
- 
-     if (!EXPECT(GC_thr_initialized, TRUE))
-       GC_thr_init();
-@@ -722,6 +724,31 @@ GC_INNER void GC_push_all_stacks(void)
+     GC_bool found_me = FALSE;
+     size_t nthreads = 0;
+     int i;
+@@ -851,6 +853,31 @@ 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 */

configure.ac

@@ -41,8 +41,6 @@ AC_DEFINE_UNQUOTED(SYSTEM, ["$system"], [platform identifier ('cpu-os')])
 test "$localstatedir" = '${prefix}/var' && localstatedir=/nix/var
 
 
-CFLAGS=
-CXXFLAGS=
 AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_CPP
@@ -177,7 +175,7 @@ fi
 PKG_CHECK_MODULES([OPENSSL], [libcrypto], [CXXFLAGS="$OPENSSL_CFLAGS $CXXFLAGS"])
 
 
-# Checks for libarchive
+# Look for libarchive.
 PKG_CHECK_MODULES([LIBARCHIVE], [libarchive >= 3.1.2], [CXXFLAGS="$LIBARCHIVE_CFLAGS $CXXFLAGS"])
 # Workaround until https://github.com/libarchive/libarchive/issues/1446 is fixed
 if test "$shared" != yes; then

doc/manual/book.toml

@@ -1,7 +1,21 @@
+[book]
+title = "Nix Reference Manual"
+
 [output.html]
 additional-css = ["custom.css"]
 additional-js = ["redirects.js"]
+edit-url-template = "https://github.com/NixOS/nix/tree/master/doc/manual/{path}"
+git-repository-url = "https://github.com/NixOS/nix"
 
 [preprocessor.anchors]
 renderers = ["html"]
 command = "jq --from-file doc/manual/anchors.jq"
+
+[output.linkcheck]
+# no Internet during the build (in the sandbox)
+follow-web-links = false
+
+# mdbook-linkcheck does not understand [foo]{#bar} style links, resulting in
+# excessive "Potential incomplete link" warnings. No other kind of warning was
+# produced at the time of writing.
+warning-policy = "ignore"

doc/manual/generate-builtins.nix

@@ -1,16 +1,20 @@
-with builtins;
-with import ./utils.nix;
+builtinsDump:
+let
+  showBuiltin = name:
+    let
+      inherit (builtinsDump.${name}) doc args;
+    in
+    ''
+      <dt id="builtins-${name}">
+        <a href="#builtins-${name}"><code>${name} ${listArgs args}</code></a>
+      </dt>
+      <dd>
 
-builtins:
+        ${doc}
+
+      </dd>
+    '';
+  listArgs = args: builtins.concatStringsSep " " (map (s: "<var>${s}</var>") args);
+in
+with builtins; concatStringsSep "\n" (map showBuiltin (attrNames builtinsDump))
 
-concatStrings (map
-  (name:
-    let builtin = builtins.${name}; in
-    "<dt id=\"builtins-${name}\"><a href=\"#builtins-${name}\"><code>${name} "
-    + concatStringsSep " " (map (s: "<var>${s}</var>") builtin.args)
-    + "</code></a></dt>"
-    + "<dd>\n\n"
-    + builtin.doc
-    + "\n\n</dd>"
-  )
-  (attrNames builtins))

doc/manual/generate-manpage.nix

@@ -1,11 +1,11 @@
-{ command }:
+{ toplevel }:
 
 with builtins;
 with import ./utils.nix;
 
 let
 
-  showCommand = { command, details, filename }:
+  showCommand = { command, details, filename, toplevel }:
     let
       result = ''
         > **Warning** \
@@ -57,14 +57,15 @@ let
       maybeOptions = if details.flags == {} then "" else ''
         # Options
 
-        ${showOptions details.flags}
+        ${showOptions details.flags toplevel.flags}
       '';
-      showOptions = options:
+      showOptions = options: commonOptions:
         let
+          allOptions = options // commonOptions;
           showCategory = cat: ''
             ${if cat != "" then "**${cat}:**" else ""}
 
-            ${listOptions (filterAttrs (n: v: v.category == cat) options)}
+            ${listOptions (filterAttrs (n: v: v.category == cat) allOptions)}
             '';
           listOptions = opts: concatStringsSep "\n" (attrValues (mapAttrs showOption opts));
           showOption = name: option:
@@ -76,30 +77,34 @@ let
 
                 ${option.description}
             '';
-          categories = sort builtins.lessThan (unique (map (cmd: cmd.category) (attrValues options)));
+          categories = sort builtins.lessThan (unique (map (cmd: cmd.category) (attrValues allOptions)));
         in concatStrings (map showCategory categories);
     in squash result;
 
   appendName = filename: name: (if filename == "nix" then "nix3" else filename) + "-" + name;
 
-  processCommand = { command, details, filename }:
+  processCommand = { command, details, filename, toplevel }:
     let
       cmd = {
         inherit command;
         name = filename + ".md";
-        value = showCommand { inherit command details filename; };
+        value = showCommand { inherit command details filename toplevel; };
       };
       subcommand = subCmd: processCommand {
         command = command + " " + subCmd;
         details = details.commands.${subCmd};
         filename = appendName filename subCmd;
+        inherit toplevel;
       };
     in [ cmd ] ++ concatMap subcommand (attrNames details.commands or {});
 
+  parsedToplevel = builtins.fromJSON toplevel;
+  
   manpages = processCommand {
     command = "nix";
-    details = builtins.fromJSON command;
+    details = parsedToplevel;
     filename = "nix";
+    toplevel = parsedToplevel;
   };
 
   tableOfContents = let

doc/manual/generate-options.nix

@@ -1,29 +1,41 @@
-with builtins;
-with import ./utils.nix;
+let
+  inherit (builtins) attrNames concatStringsSep isAttrs isBool;
+  inherit (import ./utils.nix) concatStrings squash splitLines;
+in
 
-options:
+optionsInfo:
+let
+  showOption = name:
+    let
+      inherit (optionsInfo.${name}) description documentDefault defaultValue aliases;
+      result = squash ''
+          - <span id="conf-${name}">[`${name}`](#conf-${name})</span>
 
-concatStrings (map
-  (name:
-    let option = options.${name}; in
-    "  - [`${name}`](#conf-${name})"
-    + "<p id=\"conf-${name}\"></p>\n\n"
-    + concatStrings (map (s: "    ${s}\n") (splitLines option.description)) + "\n\n"
-    + (if option.documentDefault
-       then "    **Default:** " + (
-       if option.value == "" || option.value == []
-       then "*empty*"
-       else if isBool option.value
-       then (if option.value then "`true`" else "`false`")
-       else
-         # n.b. a StringMap value type is specified as a string, but
-         # this shows the value type.  The empty stringmap is "null" in
-         # JSON, but that converts to "{ }" here.
-         (if isAttrs option.value then "`\"\"`"
-          else "`" + toString option.value + "`")) + "\n\n"
-       else "    **Default:** *machine-specific*\n")
-    + (if option.aliases != []
-       then "    **Deprecated alias:** " + (concatStringsSep ", " (map (s: "`${s}`") option.aliases)) + "\n\n"
-       else "")
-    )
-  (attrNames options))
+          ${indent "  " body}
+        '';
+      # separate body to cleanly handle indentation
+      body = ''
+          ${description}
+
+          **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:
+          if aliases == [] then "" else
+            "**Deprecated alias:** ${(concatStringsSep ", " (map (s: "`${s}`") aliases))}";
+      indent = prefix: s:
+        concatStringsSep "\n" (map (x: if x == "" then x else "${prefix}${x}") (splitLines s));
+      in result;
+in concatStrings (map showOption (attrNames optionsInfo))

doc/manual/local.mk

@@ -29,19 +29,19 @@ nix-eval = $(dummy-env) $(bindir)/nix eval --experimental-features nix-command -
 $(d)/%.1: $(d)/src/command-ref/%.md
 	@printf "Title: %s\n\n" "$$(basename $@ .1)" > $^.tmp
 	@cat $^ >> $^.tmp
-	$(trace-gen) lowdown -sT man -M section=1 $^.tmp -o $@
+	$(trace-gen) lowdown -sT man --nroff-nolinks -M section=1 $^.tmp -o $@
 	@rm $^.tmp
 
 $(d)/%.8: $(d)/src/command-ref/%.md
 	@printf "Title: %s\n\n" "$$(basename $@ .8)" > $^.tmp
 	@cat $^ >> $^.tmp
-	$(trace-gen) lowdown -sT man -M section=8 $^.tmp -o $@
+	$(trace-gen) lowdown -sT man --nroff-nolinks -M section=8 $^.tmp -o $@
 	@rm $^.tmp
 
 $(d)/nix.conf.5: $(d)/src/command-ref/conf-file.md
 	@printf "Title: %s\n\n" "$$(basename $@ .5)" > $^.tmp
 	@cat $^ >> $^.tmp
-	$(trace-gen) lowdown -sT man -M section=5 $^.tmp -o $@
+	$(trace-gen) lowdown -sT man --nroff-nolinks -M section=5 $^.tmp -o $@
 	@rm $^.tmp
 
 $(d)/src/SUMMARY.md: $(d)/src/SUMMARY.md.in $(d)/src/command-ref/new-cli
@@ -50,11 +50,16 @@ $(d)/src/SUMMARY.md: $(d)/src/SUMMARY.md.in $(d)/src/command-ref/new-cli
 
 $(d)/src/command-ref/new-cli: $(d)/nix.json $(d)/generate-manpage.nix $(bindir)/nix
 	@rm -rf $@
-	$(trace-gen) $(nix-eval) --write-to $@ --expr 'import doc/manual/generate-manpage.nix { command = builtins.readFile $<; }'
+	$(trace-gen) $(nix-eval) --write-to $@.tmp --expr 'import doc/manual/generate-manpage.nix { toplevel = builtins.readFile $<; }'
+	# @docroot@: https://nixos.org/manual/nix/unstable/contributing/hacking.html#docroot-variable
+	$(trace-gen) sed -i $@.tmp/*.md -e 's^@docroot@^../..^g'
+	@mv $@.tmp $@
 
 $(d)/src/command-ref/conf-file.md: $(d)/conf-file.json $(d)/generate-options.nix $(d)/src/command-ref/conf-file-prefix.md $(bindir)/nix
 	@cat doc/manual/src/command-ref/conf-file-prefix.md > $@.tmp
-	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-options.nix (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp
+	# @docroot@: https://nixos.org/manual/nix/unstable/contributing/hacking.html#docroot-variable
+	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-options.nix (builtins.fromJSON (builtins.readFile $<))' \
+	  | sed -e 's^@docroot@^..^g'>> $@.tmp
 	@mv $@.tmp $@
 
 $(d)/nix.json: $(bindir)/nix
@@ -67,7 +72,9 @@ $(d)/conf-file.json: $(bindir)/nix
 
 $(d)/src/language/builtins.md: $(d)/builtins.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
+	# @docroot@: https://nixos.org/manual/nix/unstable/contributing/hacking.html#docroot-variable
+	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtins.nix (builtins.fromJSON (builtins.readFile $<))' \
+	  | sed -e 's^@docroot@^..^g' >> $@.tmp
 	@cat doc/manual/src/language/builtins-suffix.md >> $@.tmp
 	@mv $@.tmp $@
 
@@ -102,6 +109,12 @@ doc/manual/generated/man1/nix3-manpages: $(d)/src/command-ref/new-cli
 	@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/command-ref/conf-file.md $(d)/src/language/builtins.md
-	$(trace-gen) RUST_LOG=warn mdbook build doc/manual -d $(DESTDIR)$(docdir)/manual
+	$(trace-gen) \
+	  set -euo pipefail; \
+	  RUST_LOG=warn mdbook build doc/manual -d $(DESTDIR)$(docdir)/manual.tmp 2>&1 \
+		  | { grep -Fv "because fragment resolution isn't implemented" || :; }
+	@rm -rf $(DESTDIR)$(docdir)/manual
+	@mv $(DESTDIR)$(docdir)/manual.tmp/html $(DESTDIR)$(docdir)/manual
+	@rm -rf $(DESTDIR)$(docdir)/manual.tmp
 
 endif

doc/manual/redirects.js

@@ -1,330 +1,421 @@
-// Redirects from old DocBook manual.
-var redirects = {
-  "#part-advanced-topics": "advanced-topics/advanced-topics.html",
-  "#chap-tuning-cores-and-jobs": "advanced-topics/cores-vs-jobs.html",
-  "#chap-diff-hook": "advanced-topics/diff-hook.html",
-  "#check-dirs-are-unregistered": "advanced-topics/diff-hook.html#check-dirs-are-unregistered",
-  "#chap-distributed-builds": "advanced-topics/distributed-builds.html",
-  "#chap-post-build-hook": "advanced-topics/post-build-hook.html",
-  "#chap-post-build-hook-caveats": "advanced-topics/post-build-hook.html#implementation-caveats",
-  "#part-command-ref": "command-ref/command-ref.html",
-  "#conf-allow-import-from-derivation": "command-ref/conf-file.html#conf-allow-import-from-derivation",
-  "#conf-allow-new-privileges": "command-ref/conf-file.html#conf-allow-new-privileges",
-  "#conf-allowed-uris": "command-ref/conf-file.html#conf-allowed-uris",
-  "#conf-allowed-users": "command-ref/conf-file.html#conf-allowed-users",
-  "#conf-auto-optimise-store": "command-ref/conf-file.html#conf-auto-optimise-store",
-  "#conf-binary-cache-public-keys": "command-ref/conf-file.html#conf-binary-cache-public-keys",
-  "#conf-binary-caches": "command-ref/conf-file.html#conf-binary-caches",
-  "#conf-build-compress-log": "command-ref/conf-file.html#conf-build-compress-log",
-  "#conf-build-cores": "command-ref/conf-file.html#conf-build-cores",
-  "#conf-build-extra-chroot-dirs": "command-ref/conf-file.html#conf-build-extra-chroot-dirs",
-  "#conf-build-extra-sandbox-paths": "command-ref/conf-file.html#conf-build-extra-sandbox-paths",
-  "#conf-build-fallback": "command-ref/conf-file.html#conf-build-fallback",
-  "#conf-build-max-jobs": "command-ref/conf-file.html#conf-build-max-jobs",
-  "#conf-build-max-log-size": "command-ref/conf-file.html#conf-build-max-log-size",
-  "#conf-build-max-silent-time": "command-ref/conf-file.html#conf-build-max-silent-time",
-  "#conf-build-repeat": "command-ref/conf-file.html#conf-build-repeat",
-  "#conf-build-timeout": "command-ref/conf-file.html#conf-build-timeout",
-  "#conf-build-use-chroot": "command-ref/conf-file.html#conf-build-use-chroot",
-  "#conf-build-use-sandbox": "command-ref/conf-file.html#conf-build-use-sandbox",
-  "#conf-build-use-substitutes": "command-ref/conf-file.html#conf-build-use-substitutes",
-  "#conf-build-users-group": "command-ref/conf-file.html#conf-build-users-group",
-  "#conf-builders": "command-ref/conf-file.html#conf-builders",
-  "#conf-builders-use-substitutes": "command-ref/conf-file.html#conf-builders-use-substitutes",
-  "#conf-compress-build-log": "command-ref/conf-file.html#conf-compress-build-log",
-  "#conf-connect-timeout": "command-ref/conf-file.html#conf-connect-timeout",
-  "#conf-cores": "command-ref/conf-file.html#conf-cores",
-  "#conf-diff-hook": "command-ref/conf-file.html#conf-diff-hook",
-  "#conf-enforce-determinism": "command-ref/conf-file.html#conf-enforce-determinism",
-  "#conf-env-keep-derivations": "command-ref/conf-file.html#conf-env-keep-derivations",
-  "#conf-extra-binary-caches": "command-ref/conf-file.html#conf-extra-binary-caches",
-  "#conf-extra-platforms": "command-ref/conf-file.html#conf-extra-platforms",
-  "#conf-extra-sandbox-paths": "command-ref/conf-file.html#conf-extra-sandbox-paths",
-  "#conf-extra-substituters": "command-ref/conf-file.html#conf-extra-substituters",
-  "#conf-fallback": "command-ref/conf-file.html#conf-fallback",
-  "#conf-fsync-metadata": "command-ref/conf-file.html#conf-fsync-metadata",
-  "#conf-gc-keep-derivations": "command-ref/conf-file.html#conf-gc-keep-derivations",
-  "#conf-gc-keep-outputs": "command-ref/conf-file.html#conf-gc-keep-outputs",
-  "#conf-hashed-mirrors": "command-ref/conf-file.html#conf-hashed-mirrors",
-  "#conf-http-connections": "command-ref/conf-file.html#conf-http-connections",
-  "#conf-keep-build-log": "command-ref/conf-file.html#conf-keep-build-log",
-  "#conf-keep-derivations": "command-ref/conf-file.html#conf-keep-derivations",
-  "#conf-keep-env-derivations": "command-ref/conf-file.html#conf-keep-env-derivations",
-  "#conf-keep-outputs": "command-ref/conf-file.html#conf-keep-outputs",
-  "#conf-max-build-log-size": "command-ref/conf-file.html#conf-max-build-log-size",
-  "#conf-max-free": "command-ref/conf-file.html#conf-max-free",
-  "#conf-max-jobs": "command-ref/conf-file.html#conf-max-jobs",
-  "#conf-max-silent-time": "command-ref/conf-file.html#conf-max-silent-time",
-  "#conf-min-free": "command-ref/conf-file.html#conf-min-free",
-  "#conf-narinfo-cache-negative-ttl": "command-ref/conf-file.html#conf-narinfo-cache-negative-ttl",
-  "#conf-narinfo-cache-positive-ttl": "command-ref/conf-file.html#conf-narinfo-cache-positive-ttl",
-  "#conf-netrc-file": "command-ref/conf-file.html#conf-netrc-file",
-  "#conf-plugin-files": "command-ref/conf-file.html#conf-plugin-files",
-  "#conf-post-build-hook": "command-ref/conf-file.html#conf-post-build-hook",
-  "#conf-pre-build-hook": "command-ref/conf-file.html#conf-pre-build-hook",
-  "#conf-repeat": "command-ref/conf-file.html#conf-repeat",
-  "#conf-require-sigs": "command-ref/conf-file.html#conf-require-sigs",
-  "#conf-restrict-eval": "command-ref/conf-file.html#conf-restrict-eval",
-  "#conf-run-diff-hook": "command-ref/conf-file.html#conf-run-diff-hook",
-  "#conf-sandbox": "command-ref/conf-file.html#conf-sandbox",
-  "#conf-sandbox-dev-shm-size": "command-ref/conf-file.html#conf-sandbox-dev-shm-size",
-  "#conf-sandbox-paths": "command-ref/conf-file.html#conf-sandbox-paths",
-  "#conf-secret-key-files": "command-ref/conf-file.html#conf-secret-key-files",
-  "#conf-show-trace": "command-ref/conf-file.html#conf-show-trace",
-  "#conf-stalled-download-timeout": "command-ref/conf-file.html#conf-stalled-download-timeout",
-  "#conf-substitute": "command-ref/conf-file.html#conf-substitute",
-  "#conf-substituters": "command-ref/conf-file.html#conf-substituters",
-  "#conf-system": "command-ref/conf-file.html#conf-system",
-  "#conf-system-features": "command-ref/conf-file.html#conf-system-features",
-  "#conf-tarball-ttl": "command-ref/conf-file.html#conf-tarball-ttl",
-  "#conf-timeout": "command-ref/conf-file.html#conf-timeout",
-  "#conf-trace-function-calls": "command-ref/conf-file.html#conf-trace-function-calls",
-  "#conf-trusted-binary-caches": "command-ref/conf-file.html#conf-trusted-binary-caches",
-  "#conf-trusted-public-keys": "command-ref/conf-file.html#conf-trusted-public-keys",
-  "#conf-trusted-substituters": "command-ref/conf-file.html#conf-trusted-substituters",
-  "#conf-trusted-users": "command-ref/conf-file.html#conf-trusted-users",
-  "#extra-sandbox-paths": "command-ref/conf-file.html#extra-sandbox-paths",
-  "#sec-conf-file": "command-ref/conf-file.html",
-  "#env-NIX_PATH": "command-ref/env-common.html#env-NIX_PATH",
-  "#env-common": "command-ref/env-common.html",
-  "#envar-remote": "command-ref/env-common.html#env-NIX_REMOTE",
-  "#sec-common-env": "command-ref/env-common.html",
-  "#ch-files": "command-ref/files.html",
-  "#ch-main-commands": "command-ref/main-commands.html",
-  "#opt-out-link": "command-ref/nix-build.html#opt-out-link",
-  "#sec-nix-build": "command-ref/nix-build.html",
-  "#sec-nix-channel": "command-ref/nix-channel.html",
-  "#sec-nix-collect-garbage": "command-ref/nix-collect-garbage.html",
-  "#sec-nix-copy-closure": "command-ref/nix-copy-closure.html",
-  "#sec-nix-daemon": "command-ref/nix-daemon.html",
-  "#refsec-nix-env-install-examples": "command-ref/nix-env.html#examples",
-  "#rsec-nix-env-install": "command-ref/nix-env.html#operation---install",
-  "#rsec-nix-env-set": "command-ref/nix-env.html#operation---set",
-  "#rsec-nix-env-set-flag": "command-ref/nix-env.html#operation---set-flag",
-  "#rsec-nix-env-upgrade": "command-ref/nix-env.html#operation---upgrade",
-  "#sec-nix-env": "command-ref/nix-env.html",
-  "#ssec-version-comparisons": "command-ref/nix-env.html#versions",
-  "#sec-nix-hash": "command-ref/nix-hash.html",
-  "#sec-nix-instantiate": "command-ref/nix-instantiate.html",
-  "#sec-nix-prefetch-url": "command-ref/nix-prefetch-url.html",
-  "#sec-nix-shell": "command-ref/nix-shell.html",
-  "#ssec-nix-shell-shebang": "command-ref/nix-shell.html#use-as-a--interpreter",
-  "#nixref-queries": "command-ref/nix-store.html#queries",
-  "#opt-add-root": "command-ref/nix-store.html#opt-add-root",
-  "#refsec-nix-store-dump": "command-ref/nix-store.html#operation---dump",
-  "#refsec-nix-store-export": "command-ref/nix-store.html#operation---export",
-  "#refsec-nix-store-import": "command-ref/nix-store.html#operation---import",
-  "#refsec-nix-store-query": "command-ref/nix-store.html#operation---query",
-  "#refsec-nix-store-verify": "command-ref/nix-store.html#operation---verify",
-  "#rsec-nix-store-gc": "command-ref/nix-store.html#operation---gc",
-  "#rsec-nix-store-generate-binary-cache-key": "command-ref/nix-store.html#operation---generate-binary-cache-key",
-  "#rsec-nix-store-realise": "command-ref/nix-store.html#operation---realise",
-  "#rsec-nix-store-serve": "command-ref/nix-store.html#operation---serve",
-  "#sec-nix-store": "command-ref/nix-store.html",
-  "#opt-I": "command-ref/opt-common.html#opt-I",
-  "#opt-attr": "command-ref/opt-common.html#opt-attr",
-  "#opt-common": "command-ref/opt-common.html",
-  "#opt-cores": "command-ref/opt-common.html#opt-cores",
-  "#opt-log-format": "command-ref/opt-common.html#opt-log-format",
-  "#opt-max-jobs": "command-ref/opt-common.html#opt-max-jobs",
-  "#opt-max-silent-time": "command-ref/opt-common.html#opt-max-silent-time",
-  "#opt-timeout": "command-ref/opt-common.html#opt-timeout",
-  "#sec-common-options": "command-ref/opt-common.html",
-  "#ch-utilities": "command-ref/utilities.html",
-  "#chap-hacking": "contributing/hacking.html",
-  "#adv-attr-allowSubstitutes": "language/advanced-attributes.html#adv-attr-allowSubstitutes",
-  "#adv-attr-allowedReferences": "language/advanced-attributes.html#adv-attr-allowedReferences",
-  "#adv-attr-allowedRequisites": "language/advanced-attributes.html#adv-attr-allowedRequisites",
-  "#adv-attr-disallowedReferences": "language/advanced-attributes.html#adv-attr-disallowedReferences",
-  "#adv-attr-disallowedRequisites": "language/advanced-attributes.html#adv-attr-disallowedRequisites",
-  "#adv-attr-exportReferencesGraph": "language/advanced-attributes.html#adv-attr-exportReferencesGraph",
-  "#adv-attr-impureEnvVars": "language/advanced-attributes.html#adv-attr-impureEnvVars",
-  "#adv-attr-outputHash": "language/advanced-attributes.html#adv-attr-outputHash",
-  "#adv-attr-outputHashAlgo": "language/advanced-attributes.html#adv-attr-outputHashAlgo",
-  "#adv-attr-outputHashMode": "language/advanced-attributes.html#adv-attr-outputHashMode",
-  "#adv-attr-passAsFile": "language/advanced-attributes.html#adv-attr-passAsFile",
-  "#adv-attr-preferLocalBuild": "language/advanced-attributes.html#adv-attr-preferLocalBuild",
-  "#fixed-output-drvs": "language/advanced-attributes.html#adv-attr-outputHash",
-  "#sec-advanced-attributes": "language/advanced-attributes.html",
-  "#builtin-abort": "language/builtins.html#builtins-abort",
-  "#builtin-add": "language/builtins.html#builtins-add",
-  "#builtin-all": "language/builtins.html#builtins-all",
-  "#builtin-any": "language/builtins.html#builtins-any",
-  "#builtin-attrNames": "language/builtins.html#builtins-attrNames",
-  "#builtin-attrValues": "language/builtins.html#builtins-attrValues",
-  "#builtin-baseNameOf": "language/builtins.html#builtins-baseNameOf",
-  "#builtin-bitAnd": "language/builtins.html#builtins-bitAnd",
-  "#builtin-bitOr": "language/builtins.html#builtins-bitOr",
-  "#builtin-bitXor": "language/builtins.html#builtins-bitXor",
-  "#builtin-builtins": "language/builtins.html#builtins-builtins",
-  "#builtin-compareVersions": "language/builtins.html#builtins-compareVersions",
-  "#builtin-concatLists": "language/builtins.html#builtins-concatLists",
-  "#builtin-concatStringsSep": "language/builtins.html#builtins-concatStringsSep",
-  "#builtin-currentSystem": "language/builtins.html#builtins-currentSystem",
-  "#builtin-deepSeq": "language/builtins.html#builtins-deepSeq",
-  "#builtin-derivation": "language/builtins.html#builtins-derivation",
-  "#builtin-dirOf": "language/builtins.html#builtins-dirOf",
-  "#builtin-div": "language/builtins.html#builtins-div",
-  "#builtin-elem": "language/builtins.html#builtins-elem",
-  "#builtin-elemAt": "language/builtins.html#builtins-elemAt",
-  "#builtin-fetchGit": "language/builtins.html#builtins-fetchGit",
-  "#builtin-fetchTarball": "language/builtins.html#builtins-fetchTarball",
-  "#builtin-fetchurl": "language/builtins.html#builtins-fetchurl",
-  "#builtin-filterSource": "language/builtins.html#builtins-filterSource",
-  "#builtin-foldl-prime": "language/builtins.html#builtins-foldl-prime",
-  "#builtin-fromJSON": "language/builtins.html#builtins-fromJSON",
-  "#builtin-functionArgs": "language/builtins.html#builtins-functionArgs",
-  "#builtin-genList": "language/builtins.html#builtins-genList",
-  "#builtin-getAttr": "language/builtins.html#builtins-getAttr",
-  "#builtin-getEnv": "language/builtins.html#builtins-getEnv",
-  "#builtin-hasAttr": "language/builtins.html#builtins-hasAttr",
-  "#builtin-hashFile": "language/builtins.html#builtins-hashFile",
-  "#builtin-hashString": "language/builtins.html#builtins-hashString",
-  "#builtin-head": "language/builtins.html#builtins-head",
-  "#builtin-import": "language/builtins.html#builtins-import",
-  "#builtin-intersectAttrs": "language/builtins.html#builtins-intersectAttrs",
-  "#builtin-isAttrs": "language/builtins.html#builtins-isAttrs",
-  "#builtin-isBool": "language/builtins.html#builtins-isBool",
-  "#builtin-isFloat": "language/builtins.html#builtins-isFloat",
-  "#builtin-isFunction": "language/builtins.html#builtins-isFunction",
-  "#builtin-isInt": "language/builtins.html#builtins-isInt",
-  "#builtin-isList": "language/builtins.html#builtins-isList",
-  "#builtin-isNull": "language/builtins.html#builtins-isNull",
-  "#builtin-isString": "language/builtins.html#builtins-isString",
-  "#builtin-length": "language/builtins.html#builtins-length",
-  "#builtin-lessThan": "language/builtins.html#builtins-lessThan",
-  "#builtin-listToAttrs": "language/builtins.html#builtins-listToAttrs",
-  "#builtin-map": "language/builtins.html#builtins-map",
-  "#builtin-match": "language/builtins.html#builtins-match",
-  "#builtin-mul": "language/builtins.html#builtins-mul",
-  "#builtin-parseDrvName": "language/builtins.html#builtins-parseDrvName",
-  "#builtin-path": "language/builtins.html#builtins-path",
-  "#builtin-pathExists": "language/builtins.html#builtins-pathExists",
-  "#builtin-placeholder": "language/builtins.html#builtins-placeholder",
-  "#builtin-readDir": "language/builtins.html#builtins-readDir",
-  "#builtin-readFile": "language/builtins.html#builtins-readFile",
-  "#builtin-removeAttrs": "language/builtins.html#builtins-removeAttrs",
-  "#builtin-replaceStrings": "language/builtins.html#builtins-replaceStrings",
-  "#builtin-seq": "language/builtins.html#builtins-seq",
-  "#builtin-sort": "language/builtins.html#builtins-sort",
-  "#builtin-split": "language/builtins.html#builtins-split",
-  "#builtin-splitVersion": "language/builtins.html#builtins-splitVersion",
-  "#builtin-stringLength": "language/builtins.html#builtins-stringLength",
-  "#builtin-sub": "language/builtins.html#builtins-sub",
-  "#builtin-substring": "language/builtins.html#builtins-substring",
-  "#builtin-tail": "language/builtins.html#builtins-tail",
-  "#builtin-throw": "language/builtins.html#builtins-throw",
-  "#builtin-toFile": "language/builtins.html#builtins-toFile",
-  "#builtin-toJSON": "language/builtins.html#builtins-toJSON",
-  "#builtin-toPath": "language/builtins.html#builtins-toPath",
-  "#builtin-toString": "language/builtins.html#builtins-toString",
-  "#builtin-toXML": "language/builtins.html#builtins-toXML",
-  "#builtin-trace": "language/builtins.html#builtins-trace",
-  "#builtin-tryEval": "language/builtins.html#builtins-tryEval",
-  "#builtin-typeOf": "language/builtins.html#builtins-typeOf",
-  "#ssec-builtins": "language/builtins.html",
-  "#attr-system": "language/derivations.html#attr-system",
-  "#ssec-derivation": "language/derivations.html",
-  "#ch-expression-language": "language/index.html",
-  "#sec-constructs": "language/constructs.html",
-  "#sect-let-language": "language/constructs.html#let-language",
-  "#ss-functions": "language/constructs.html#functions",
-  "#sec-language-operators": "language/operators.html",
-  "#table-operators": "language/operators.html",
-  "#ssec-values": "language/values.html",
-  "#gloss-closure": "glossary.html#gloss-closure",
-  "#gloss-derivation": "glossary.html#gloss-derivation",
-  "#gloss-deriver": "glossary.html#gloss-deriver",
-  "#gloss-nar": "glossary.html#gloss-nar",
-  "#gloss-output-path": "glossary.html#gloss-output-path",
-  "#gloss-profile": "glossary.html#gloss-profile",
-  "#gloss-reachable": "glossary.html#gloss-reachable",
-  "#gloss-reference": "glossary.html#gloss-reference",
-  "#gloss-substitute": "glossary.html#gloss-substitute",
-  "#gloss-user-env": "glossary.html#gloss-user-env",
-  "#gloss-validity": "glossary.html#gloss-validity",
-  "#part-glossary": "glossary.html",
-  "#sec-building-source": "installation/building-source.html",
-  "#ch-env-variables": "installation/env-variables.html",
-  "#sec-installer-proxy-settings": "installation/env-variables.html#proxy-environment-variables",
-  "#sec-nix-ssl-cert-file": "installation/env-variables.html#nix_ssl_cert_file",
-  "#sec-nix-ssl-cert-file-with-nix-daemon-and-macos": "installation/env-variables.html#nix_ssl_cert_file-with-macos-and-the-nix-daemon",
-  "#chap-installation": "installation/installation.html",
-  "#ch-installing-binary": "installation/installing-binary.html",
-  "#sect-macos-installation": "installation/installing-binary.html#macos-installation",
-  "#sect-macos-installation-change-store-prefix": "installation/installing-binary.html#macos-installation",
-  "#sect-macos-installation-encrypted-volume": "installation/installing-binary.html#macos-installation",
-  "#sect-macos-installation-recommended-notes": "installation/installing-binary.html#macos-installation",
-  "#sect-macos-installation-symlink": "installation/installing-binary.html#macos-installation",
-  "#sect-multi-user-installation": "installation/installing-binary.html#multi-user-installation",
-  "#sect-nix-install-binary-tarball": "installation/installing-binary.html#installing-from-a-binary-tarball",
-  "#sect-nix-install-pinned-version-url": "installation/installing-binary.html#installing-a-pinned-nix-version-from-a-url",
-  "#sect-single-user-installation": "installation/installing-binary.html#single-user-installation",
-  "#ch-installing-source": "installation/installing-source.html",
-  "#ssec-multi-user": "installation/multi-user.html",
-  "#ch-nix-security": "installation/nix-security.html",
-  "#sec-obtaining-source": "installation/obtaining-source.html",
-  "#sec-prerequisites-source": "installation/prerequisites-source.html",
-  "#sec-single-user": "installation/single-user.html",
-  "#ch-supported-platforms": "installation/supported-platforms.html",
-  "#ch-upgrading-nix": "installation/upgrading.html",
-  "#ch-about-nix": "introduction.html",
-  "#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",
-  "#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",
-  "#chap-package-management": "package-management/package-management.html",
-  "#sec-profiles": "package-management/profiles.html",
-  "#ssec-s3-substituter": "package-management/s3-substituter.html",
-  "#ssec-s3-substituter-anonymous-reads": "package-management/s3-substituter.html#anonymous-reads-to-your-s3-compatible-binary-cache",
-  "#ssec-s3-substituter-authenticated-reads": "package-management/s3-substituter.html#authenticated-reads-to-your-s3-binary-cache",
-  "#ssec-s3-substituter-authenticated-writes": "package-management/s3-substituter.html#authenticated-writes-to-your-s3-compatible-binary-cache",
-  "#sec-sharing-packages": "package-management/sharing-packages.html",
-  "#ssec-ssh-substituter": "package-management/ssh-substituter.html",
-  "#chap-quick-start": "quick-start.html",
-  "#sec-relnotes": "release-notes/release-notes.html",
-  "#ch-relnotes-0.10.1": "release-notes/rl-0.10.1.html",
-  "#ch-relnotes-0.10": "release-notes/rl-0.10.html",
-  "#ssec-relnotes-0.11": "release-notes/rl-0.11.html",
-  "#ssec-relnotes-0.12": "release-notes/rl-0.12.html",
-  "#ssec-relnotes-0.13": "release-notes/rl-0.13.html",
-  "#ssec-relnotes-0.14": "release-notes/rl-0.14.html",
-  "#ssec-relnotes-0.15": "release-notes/rl-0.15.html",
-  "#ssec-relnotes-0.16": "release-notes/rl-0.16.html",
-  "#ch-relnotes-0.5": "release-notes/rl-0.5.html",
-  "#ch-relnotes-0.6": "release-notes/rl-0.6.html",
-  "#ch-relnotes-0.7": "release-notes/rl-0.7.html",
-  "#ch-relnotes-0.8.1": "release-notes/rl-0.8.1.html",
-  "#ch-relnotes-0.8": "release-notes/rl-0.8.html",
-  "#ch-relnotes-0.9.1": "release-notes/rl-0.9.1.html",
-  "#ch-relnotes-0.9.2": "release-notes/rl-0.9.2.html",
-  "#ch-relnotes-0.9": "release-notes/rl-0.9.html",
-  "#ssec-relnotes-1.0": "release-notes/rl-1.0.html",
-  "#ssec-relnotes-1.1": "release-notes/rl-1.1.html",
-  "#ssec-relnotes-1.10": "release-notes/rl-1.10.html",
-  "#ssec-relnotes-1.11.10": "release-notes/rl-1.11.10.html",
-  "#ssec-relnotes-1.11": "release-notes/rl-1.11.html",
-  "#ssec-relnotes-1.2": "release-notes/rl-1.2.html",
-  "#ssec-relnotes-1.3": "release-notes/rl-1.3.html",
-  "#ssec-relnotes-1.4": "release-notes/rl-1.4.html",
-  "#ssec-relnotes-1.5.1": "release-notes/rl-1.5.1.html",
-  "#ssec-relnotes-1.5.2": "release-notes/rl-1.5.2.html",
-  "#ssec-relnotes-1.5": "release-notes/rl-1.5.html",
-  "#ssec-relnotes-1.6.1": "release-notes/rl-1.6.1.html",
-  "#ssec-relnotes-1.6.0": "release-notes/rl-1.6.html",
-  "#ssec-relnotes-1.7": "release-notes/rl-1.7.html",
-  "#ssec-relnotes-1.8": "release-notes/rl-1.8.html",
-  "#ssec-relnotes-1.9": "release-notes/rl-1.9.html",
-  "#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"
+// redirect rules for anchors ensure backwards compatibility of URLs.
+// this must be done on the client side, as web servers do not see the anchor part of the URL.
+
+// redirections are declared as follows:
+// each entry has as its key a path matching the requested URL path, relative to the mdBook document root.
+//
+//     IMPORTANT: it must specify the full path with file name and suffix
+//
+// each entry is itself a set of key-value pairs, where
+// - keys are anchors on the matched path.
+// - values are redirection targets relative to the current path.
+
+const redirects = {
+ "index.html": {
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+    "ch-relnotes-0.8": "release-notes/rl-0.8.html",
+    "ch-relnotes-0.9.1": "release-notes/rl-0.9.1.html",
+    "ch-relnotes-0.9.2": "release-notes/rl-0.9.2.html",
+    "ch-relnotes-0.9": "release-notes/rl-0.9.html",
+    "ssec-relnotes-1.0": "release-notes/rl-1.0.html",
+    "ssec-relnotes-1.1": "release-notes/rl-1.1.html",
+    "ssec-relnotes-1.10": "release-notes/rl-1.10.html",
+    "ssec-relnotes-1.11.10": "release-notes/rl-1.11.10.html",
+    "ssec-relnotes-1.11": "release-notes/rl-1.11.html",
+    "ssec-relnotes-1.2": "release-notes/rl-1.2.html",
+    "ssec-relnotes-1.3": "release-notes/rl-1.3.html",
+    "ssec-relnotes-1.4": "release-notes/rl-1.4.html",
+    "ssec-relnotes-1.5.1": "release-notes/rl-1.5.1.html",
+    "ssec-relnotes-1.5.2": "release-notes/rl-1.5.2.html",
+    "ssec-relnotes-1.5": "release-notes/rl-1.5.html",
+    "ssec-relnotes-1.6.1": "release-notes/rl-1.6.1.html",
+    "ssec-relnotes-1.6.0": "release-notes/rl-1.6.html",
+    "ssec-relnotes-1.7": "release-notes/rl-1.7.html",
+    "ssec-relnotes-1.8": "release-notes/rl-1.8.html",
+    "ssec-relnotes-1.9": "release-notes/rl-1.9.html",
+    "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"
+  },
+  "language/values.html": {
+    "simple-values": "#primitives",
+    "lists": "#list",
+    "strings": "#string",
+    "lists": "#list",
+    "attribute-sets": "#attribute-set"
+  }
 };
 
-var isRoot = (document.location.pathname.endsWith('/') || document.location.pathname.endsWith('/index.html')) && path_to_root === '';
-if (isRoot && redirects[document.location.hash]) {
-  document.location.href = path_to_root + redirects[document.location.hash];
+// the following code matches the current page's URL against the set of redirects.
+//
+// it is written to minimize the latency between page load and redirect.
+// therefore we avoid function calls, copying data, and unnecessary loops.
+// IMPORTANT: we use stateful array operations and their order matters!
+//
+// matching URLs is more involved than it should be:
+//
+// 1. `document.location.pathname` can have an arbitrary prefix.
+//
+// 2. `path_to_root` is set by mdBook. it consists only of `../`s and
+//    determines the depth of `<path>` relative to the prefix:
+//
+//          `document.location.pathname`
+//        |------------------------------|
+//        /<prefix>/<path>/[<file>[.html]][#<anchor>]
+//                  |----|
+//              `path_to_root` has same number of path segments
+//
+//    source: https://phaiax.github.io/mdBook/format/theme/index-hbs.html#data
+//
+// 3. the following paths are equivalent:
+//
+//        /foo/bar/
+//        /foo/bar/index.html
+//        /foo/bar/index
+//
+//  4. the following paths are also equivalent:
+//
+//        /foo/bar/baz
+//        /foo/bar/baz.html
+//
+
+let segments = document.location.pathname.split('/');
+
+let file = segments.pop();
+
+// normalize file name
+if (file === '') { file = "index.html"; }
+else if (!file.endsWith('.html')) { file = file + '.html'; }
+
+segments.push(file);
+
+// use `path_to_root` to discern prefix from path.
+const depth = path_to_root.split('/').length;
+
+// remove segments containing prefix. the following works because
+// 1. the original `document.location.pathname` is absolute,
+//    hence first element of `segments` is always empty.
+// 2. last element of splitting `path_to_root` is also always empty.
+// 3. last element of `segments` is the file name.
+//
+// visual example:
+//
+//     '/foo/bar/baz.html'.split('/') -> [ '', 'foo', 'bar', 'baz.html' ]
+//          '../'.split('/')          -> [ '..', '' ]
+//
+// the following operations will then result in
+//
+//     path = 'bar/baz.html'
+//
+segments.splice(0, segments.length - depth);
+const path = segments.join('/');
+
+// anchor starts with the hash character (`#`),
+// but our redirect declarations don't, so we strip it.
+// example:
+//     document.location.hash -> '#foo'
+//     document.location.hash.substring(1) -> 'foo'
+const anchor = document.location.hash.substring(1);
+
+const redirect = redirects[path];
+if (redirect) {
+  const target = redirect[anchor];
+  if (target) {
+    document.location.href = target;
+  }
 }

doc/manual/src/SUMMARY.md.in

@@ -29,6 +29,7 @@
 - [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)
@@ -59,12 +60,14 @@
 @manpages@
   - [Files](command-ref/files.md)
     - [nix.conf](command-ref/conf-file.md)
+- [Architecture](architecture/architecture.md)
 - [Glossary](glossary.md)
 - [Contributing](contributing/contributing.md)
   - [Hacking](contributing/hacking.md)
   - [CLI guideline](contributing/cli-guideline.md)
 - [Release Notes](release-notes/release-notes.md)
-  - [Release X.Y (202?-??-??)](release-notes/rl-next.md)
+  - [Release 2.13 (2023-01-17)](release-notes/rl-2.13.md)
+  - [Release 2.12 (2022-12-06)](release-notes/rl-2.12.md)
   - [Release 2.11 (2022-08-25)](release-notes/rl-2.11.md)
   - [Release 2.10 (2022-07-11)](release-notes/rl-2.10.md)
   - [Release 2.9 (2022-05-30)](release-notes/rl-2.9.md)

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

@@ -121,37 +121,3 @@ error:
     are not valid, so checking is not possible
 
 Run the build without `--check`, and then try with `--check` again.
-
-# Automatic and Optionally Enforced Determinism Verification
-
-Automatically verify every build at build time by executing the build
-multiple times.
-
-Setting `repeat` and `enforce-determinism` in your `nix.conf` permits
-the automated verification of every build Nix performs.
-
-The following configuration will run each build three times, and will
-require the build to be deterministic:
-
-    enforce-determinism = true
-    repeat = 2
-
-Setting `enforce-determinism` to false as in the following
-configuration will run the build multiple times, execute the build
-hook, but will allow the build to succeed even if it does not build
-reproducibly:
-
-    enforce-determinism = false
-    repeat = 1
-
-An example output of this configuration:
-
-```console
-$ nix-build ./test.nix -A unstable
-this derivation will be built:
-  /nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv
-building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 1/2)...
-building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 2/2)...
-output '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable' of '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' differs from '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable.check' from previous round
-/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable
-```

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

@@ -33,12 +33,17 @@ distribute the public key for verifying the authenticity of the paths.
 example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
 ```
 
-Then, add the public key and the cache URL to your `nix.conf`'s
-`trusted-public-keys` and `substituters` options:
+Then update [`nix.conf`](../command-ref/conf-file.md) on any machine that will access the cache.
+Add the cache URL to [`substituters`](../command-ref/conf-file.md#conf-substituters) and the public key to [`trusted-public-keys`](../command-ref/conf-file.md#conf-trusted-public-keys):
 
     substituters = https://cache.nixos.org/ s3://example-nix-cache
     trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
 
+Machines that build for the cache must sign derivations using the private key.
+On those machines, add the path to the key file to the [`secret-key-files`](../command-ref/conf-file.md#conf-secret-key-files) field in their [`nix.conf`](../command-ref/conf-file.md):
+
+    secret-key-files = /etc/nix/key.private
+
 We will restart the Nix daemon in a later step.
 
 # Implementing the build hook
@@ -52,14 +57,12 @@ set -eu
 set -f # disable globbing
 export IFS=' '
 
-echo "Signing paths" $OUT_PATHS
-nix store sign --key-file /etc/nix/key.private $OUT_PATHS
 echo "Uploading paths" $OUT_PATHS
-exec nix copy --to 's3://example-nix-cache' $OUT_PATHS
+exec nix copy --to "s3://example-nix-cache" $OUT_PATHS
 ```
 
 > **Note**
-> 
+>
 > The `$OUT_PATHS` variable is a space-separated list of Nix store
 > paths. In this case, we expect and want the shell to perform word
 > splitting to make each output path its own argument to `nix

doc/manual/src/architecture/architecture.md

@@ -0,0 +1,115 @@
+# Architecture
+
+This chapter describes how Nix works.
+It should help users understand why Nix behaves as it does, and it should help developers understand how to modify Nix and how to write similar tools.
+
+## Overview
+
+Nix consists of [hierarchical layers].
+
+[hierarchical layers]: https://en.m.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
+
+```
+
+   .----------------.
+   | Nix expression |----------.
+   '----------------'          |
+           |              passed to
+           |                   |
++----------|-------------------|--------------------------------+
+| Nix      |                   V                                |
+|          |      +-------------------------+                   |
+|          |      | commmand line interface |------.            |
+|          |      +-------------------------+      |            |
+|          |                   |                   |            |
+|    evaluated by            calls              manages         |
+|          |                   |                   |            |
+|          |                   V                   |            |
+|          |         +--------------------+        |            |
+|          '-------->| language evaluator |        |            |
+|                    +--------------------+        |            |
+|                              |                   |            |
+|                           produces               |            |
+|                              |                   V            |
+| +----------------------------|------------------------------+ |
+| | store                      |                              | |
+| |            referenced by   V       builds                 | |
+| | .-------------.      .------------.      .--------------. | |
+| | | build input |----->| build plan |----->| build result | | |
+| | '-------------'      '------------'      '--------------' | |
+| +-------------------------------------------------|---------+ |
++---------------------------------------------------|-----------+
+                                                    |
+                                              represented as
+                                                    |
+                                                    V
+                                            .---------------.
+                                            |     file      |
+                                            '---------------'
+```
+
+At the top is the [command line interface](../command-ref/command-ref.md) that drives the underlying layers.
+
+The [Nix language](../language/index.md) evaluator transforms Nix expressions into self-contained *build plans*, which are used to derive *build results* from referenced *build inputs*.
+
+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.
+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.
+
+> **Important**
+> A build task in Nix is called [derivation](../glossary.md#gloss-derivation).
+
+Each build task has a special build input executed as *build instructions* in order to perform the build.
+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
+
+```
++--------------------------------------------------------------------+
+| build plan                                                         |
+|                                                                    |
+| .-------------.                                                    |
+| | build input |---------.                                          |
+| '-------------'         |                                          |
+|                    instructions                                    |
+|                         |                                          |
+|                         v                                          |
+| .-------------.    .----------.                                    |
+| | build input |-->( build task )-------.                           |
+| '-------------'    '----------'        |                           |
+|                                  instructions                      |
+|                                        |                           |
+|                                        v                           |
+| .-------------.                  .----------.     .--------------. |
+| | build input |---------.       ( build task )--->| build result | |
+| '-------------'         |        '----------'     '--------------' |
+|                    instructions        ^                           |
+|                         |              |                           |
+|                         v              |                           |
+| .-------------.    .----------.        |                           |
+| | build input |-->( build task )-------'                           |
+| '-------------'    '----------'                                    |
+|                         ^                                          |
+|                         |                                          |
+|                         |                                          |
+| .-------------.         |                                          |
+| | build input |---------'                                          |
+| '-------------'                                                    |
+|                                                                    |
++--------------------------------------------------------------------+
+```
+

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

@@ -7,42 +7,11 @@ Most Nix commands interpret the following environment variables:
     `nix-shell`. It can have the values `pure` or `impure`.
 
   - [`NIX_PATH`]{#env-NIX_PATH}\
-    A colon-separated list of directories used to look up Nix
-    expressions enclosed in angle brackets (i.e., `<path>`). For
-    instance, the value
-
-        /home/eelco/Dev:/etc/nixos
-
-    will cause Nix to look for paths relative to `/home/eelco/Dev` and
-    `/etc/nixos`, in this order. It is also possible to match paths
-    against a prefix. For example, the value
-
-        nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos
-
-    will cause Nix to search for `<nixpkgs/path>` in
-    `/home/eelco/Dev/nixpkgs-branch/path` and `/etc/nixos/nixpkgs/path`.
-
-    If a path in the Nix search path starts with `http://` or
-    `https://`, it is interpreted as the URL of a tarball that will be
-    downloaded and unpacked to a temporary location. The tarball must
-    consist of a single top-level directory. For example, setting
-    `NIX_PATH` to
-
-        nixpkgs=https://github.com/NixOS/nixpkgs/archive/master.tar.gz
-
-    tells Nix to download and use the current contents of the
-    `master` branch in the `nixpkgs` repository.
-
-    The URLs of the tarballs from the official nixos.org channels (see
-    [the manual for `nix-channel`](nix-channel.md)) can be abbreviated
-    as `channel:<channel-name>`.  For instance, the following two
-    values of `NIX_PATH` are equivalent:
-
-        nixpkgs=channel:nixos-21.05
-        nixpkgs=https://nixos.org/channels/nixos-21.05/nixexprs.tar.xz
-
-    The Nix search path can also be extended using the `-I` option to
-    many Nix commands, which takes precedence over `NIX_PATH`.
+    A colon-separated list of directories used to look up the location of Nix
+    expressions using [paths](../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](./opt-common.md#opt-I).
 
   - [`NIX_IGNORE_SYMLINK_STORE`]{#env-NIX_IGNORE_SYMLINK_STORE}\
     Normally, the Nix store directory (typically `/nix/store`) is not

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

@@ -37,10 +37,12 @@ directory containing at least a file named `default.nix`.
 
 `nix-build` is essentially a wrapper around
 [`nix-instantiate`](nix-instantiate.md) (to translate a high-level Nix
-expression to a low-level store derivation) and [`nix-store
+expression to a low-level [store derivation]) and [`nix-store
 --realise`](nix-store.md#operation---realise) (to build the store
 derivation).
 
+[store derivation]: ../glossary.md#gloss-store-derivation
+
 > **Warning**
 >
 > The result of the build is automatically registered as a root of the
@@ -53,16 +55,18 @@ All options not listed here are passed to `nix-store
 --realise`, except for `--arg` and `--attr` / `-A` which are passed to
 `nix-instantiate`.
 
-  - [`--no-out-link`]{#opt-no-out-link}\
+  - <span id="opt-no-out-link">[`--no-out-link`](#opt-no-out-link)<span>
+
     Do not create a symlink to the output path. Note that as a result
     the output does not become a root of the garbage collector, and so
-    might be deleted by `nix-store
-                    --gc`.
+    might be deleted by `nix-store --gc`.
+
+  - <span id="opt-dry-run">[`--dry-run`](#opt-dry-run)</span>
 
-  - [`--dry-run`]{#opt-dry-run}\
     Show what store paths would be built or downloaded.
 
-  - [`--out-link`]{#opt-out-link} / `-o` *outlink*\
+  - <span id="opt-out-link">[`--out-link`](#opt-out-link)</span> / `-o` *outlink*
+
     Change the name of the symlink to the output path created from
     `result` to *outlink*.
 

doc/manual/src/command-ref/nix-copy-closure.md

@@ -47,7 +47,9 @@ authentication, you can avoid typing the passphrase with `ssh-agent`.
     Enable compression of the SSH connection.
 
   - `--include-outputs`\
-    Also copy the outputs of store derivations included in the closure.
+    Also copy the outputs of [store derivation]s included in the closure.
+
+    [store derivation]: ../glossary.md#gloss-store-derivation
 
   - `--use-substitutes` / `-s`\
     Attempt to download missing paths on the target machine using Nix’s

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

@@ -8,6 +8,6 @@
 
 # Description
 
-The Nix daemon is necessary in multi-user Nix installations. It performs
-build actions and other operations on the Nix store on behalf of
+The Nix daemon is necessary in multi-user Nix installations. It runs
+build tasks and other operations on the Nix store on behalf of
 unprivileged users.

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

@@ -205,10 +205,12 @@ a number of possible ways:
     unambiguous way, which is necessary if there are multiple
     derivations with the same name.
 
-  - If *args* are store derivations, then these are
+  - If *args* are [store derivation]s, then these are
     [realised](nix-store.md#operation---realise), and the resulting output paths
     are installed.
 
+    [store derivation]: ../glossary.md#gloss-store-derivation
+
   - If *args* are store paths that are not store derivations, then these
     are [realised](nix-store.md#operation---realise) and installed.
 
@@ -280,7 +282,7 @@ To copy the store path with symbolic name `gcc` from another profile:
 $ nix-env -i --from-profile /nix/var/nix/profiles/foo gcc
 ```
 
-To install a specific store derivation (typically created by
+To install a specific [store derivation] (typically created by
 `nix-instantiate`):
 
 ```console
@@ -665,7 +667,7 @@ derivation is shown unless `--no-name` is specified.
     Print the `system` attribute of the derivation.
 
   - `--drv-path`\
-    Print the path of the store derivation.
+    Print the path of the [store derivation].
 
   - `--out-path`\
     Print the output path of the derivation.

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

@@ -17,13 +17,14 @@
 
 # Description
 
-The command `nix-instantiate` generates [store
-derivations](../glossary.md) from (high-level) Nix expressions. It
-evaluates the Nix expressions in each of *files* (which defaults to
+The command `nix-instantiate` produces [store derivation]s from (high-level) Nix expressions.
+It evaluates the Nix expressions in each of *files* (which defaults to
 *./default.nix*). Each top-level expression should evaluate to a
 derivation, a list of derivations, or a set of derivations. The paths
 of the resulting store derivations are printed on standard output.
 
+[store derivation]: ../glossary.md#gloss-store-derivation
+
 If *files* is the character `-`, then a Nix expression will be read from
 standard input.
 
@@ -79,8 +80,7 @@ standard input.
 
 # Examples
 
-Instantiating store derivations from a Nix expression, and building them
-using `nix-store`:
+Instantiate [store derivation]s from a Nix expression, and build them using `nix-store`:
 
 ```console
 $ nix-instantiate test.nix (instantiate)

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

@@ -22,7 +22,8 @@ This section lists the options that are common to all operations. These
 options are allowed for every subcommand, though they may not always
 have an effect.
 
-  - [`--add-root`]{#opt-add-root} *path*\
+  - <span id="opt-add-root">[`--add-root`](#opt-add-root)</span> *path*
+
     Causes the result of a realisation (`--realise` and
     `--force-realise`) to be registered as a root of the garbage
     collector. *path* will be created as a symlink to the resulting
@@ -71,7 +72,7 @@ paths. Realisation is a somewhat overloaded term:
     outputs are already valid, in which case we are done
     immediately. Otherwise, there may be [substitutes](../glossary.md)
     that produce the outputs (e.g., by downloading them). Finally, the
-    outputs can be produced by performing the build action described
+    outputs can be produced by running the build task described
     by the derivation.
 
   - If the store path is not a derivation, realisation ensures that the
@@ -104,10 +105,6 @@ The following flags are available:
     previous build, the new output path is left in
     `/nix/store/name.check.`
 
-    See also the `build-repeat` configuration option, which repeats a
-    derivation a number of times and prevents its outputs from being
-    registered as “valid” in the Nix store unless they are identical.
-
 Special exit codes:
 
   - `100`\
@@ -140,8 +137,10 @@ or.
 
 ## Examples
 
-This operation is typically used to build store derivations produced by
-[`nix-instantiate`](nix-instantiate.md):
+This operation is typically used to build [store derivation]s produced by
+[`nix-instantiate`](./nix-instantiate.md):
+
+[store derivation]: ../glossary.md#gloss-store-derivation
 
 ```console
 $ nix-store -r $(nix-instantiate ./test.nix)
@@ -156,6 +155,12 @@ To test whether a previously-built derivation is deterministic:
 $ nix-build '<nixpkgs>' -A hello --check -K
 ```
 
+Use [`--read-log`](#operation---read-log) to show the stderr and stdout of a build:
+
+```console
+$ nix-store --read-log $(nix-instantiate ./test.nix)
+```
+
 # Operation `--serve`
 
 ## Synopsis
@@ -301,7 +306,7 @@ symlink.
 ## Common query options
 
   - `--use-output`; `-u`\
-    For each argument to the query that is a store derivation, apply the
+    For each argument to the query that is a [store derivation], apply the
     query to the output path of the derivation instead.
 
   - `--force-realise`; `-f`\
@@ -321,7 +326,7 @@ symlink.
     This query has one option:
 
       - `--include-outputs`
-        Also include the existing output paths of store derivations,
+        Also include the existing output paths of [store derivation]s,
         and their closures.
 
     This query can be used to implement various kinds of deployment. A
@@ -375,12 +380,12 @@ symlink.
     Prints the references graph of the store paths *paths* in the
     [GraphML](http://graphml.graphdrawing.org/) file format. This can be
     used to visualise dependency graphs. To obtain a build-time
-    dependency graph, apply this to a store derivation. To obtain a
+    dependency graph, apply this to a [store derivation]. To obtain a
     runtime dependency graph, apply it to an output path.
 
   - `--binding` *name*; `-b` *name*\
     Prints the value of the attribute *name* (i.e., environment
-    variable) of the store derivations *paths*. It is an error for a
+    variable) of the [store derivation]s *paths*. It is an error for a
     derivation to not have the specified attribute.
 
   - `--hash`\

doc/manual/src/contributing/hacking.md

@@ -99,8 +99,79 @@ You can run the whole testsuite with `make check`, or the tests for a specific c
 ### Functional tests
 
 The functional tests reside under the `tests` directory and are listed in `tests/local.mk`.
-The whole testsuite can be run with `make install && make installcheck`.
-Individual tests can be run with `make tests/{testName}.sh.test`.
+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
 
@@ -178,3 +249,36 @@ 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@`.

doc/manual/src/glossary.md

@@ -1,20 +1,32 @@
 # Glossary
 
   - [derivation]{#gloss-derivation}\
-    A description of a build action. The result of a derivation is a
+    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
+    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
+
+  - [store derivation]{#gloss-store-derivation}\
+    A [derivation] represented as a `.drv` file in the [store].
+    It has a [store path], like any [store object].
+
+    Example: `/nix/store/g946hcz4c8mdvq2g8vxx42z51qb71rvp-git-2.38.1.drv`
+
+    See [`nix show-derivation`](./command-ref/new-cli/nix3-show-derivation.md) (experimental) for displaying the contents of store derivations.
+
+    [store derivation]: #gloss-store-derivation
+
   - [content-addressed derivation]{#gloss-content-addressed-derivation}\
     A derivation which has the
-    [`__contentAddressed`](language/advanced-attributes.md#adv-attr-__contentAddressed)
+    [`__contentAddressed`](./language/advanced-attributes.md#adv-attr-__contentAddressed)
     attribute set to `true`.
 
   - [fixed-output derivation]{#gloss-fixed-output-derivation}\
     A derivation which includes the
-    [`outputHash`](language/advanced-attributes.md#adv-attr-outputHash) attribute.
+    [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute.
 
   - [store]{#gloss-store}\
     The location in the file system where store objects live. Typically
@@ -34,6 +46,8 @@
       directory on another machine,  accessed via `ssh` or
       served by the `nix-serve` Perl script.
 
+    [store]: #gloss-store
+
   - [chroot store]{#gloss-chroot-store}\
     A local store whose canonical path is anything other than `/nix/store`.
 
@@ -46,15 +60,21 @@
     cache](https://cache.nixos.org).
 
   - [store path]{#gloss-store-path}\
-    The location in the file system of a store object, i.e., an
+    The location of a [store object] in the file system, i.e., an
     immediate child of the Nix store directory.
 
+    Example: `/nix/store/a040m110amc4h71lds2jmr8qrkj2jhxd-git-2.38.1`
+
+    [store path]: #gloss-store-path
+
   - [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 action), or
-    derivations (files describing a build action).
+    derivation outputs (objects produced by running a build task), or
+    derivations (files describing a build task).
+
+    [store object]: #gloss-store-object
 
   - [input-addressed store object]{#gloss-input-addressed-store-object}\
     A store object produced by building a
@@ -79,7 +99,7 @@
   - [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.html#conf-substituters).
+    [`substituters` option](./command-ref/conf-file.md#conf-substituters).
 
   - [purity]{#gloss-purity}\
     The assumption that equal Nix derivations when run always produce
@@ -124,7 +144,9 @@
     references `R` then `R` is also in the closure of `P`.
 
   - [output path]{#gloss-output-path}\
-    A store path produced by a derivation.
+    A [store path] produced by a [derivation].
+
+    [output path]: #gloss-output-path
 
   - [deriver]{#gloss-deriver}\
     The deriver of an *output path* is the store
@@ -139,7 +161,7 @@
     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*.
+    [`nix-env`](./command-ref/nix-env.md). See *profiles*.
 
   - [profile]{#gloss-profile}\
     A symlink to the current *user environment* of a user, e.g.,
@@ -150,7 +172,18 @@
     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

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

@@ -88,19 +88,51 @@ extension. The installer will also create `/etc/profile.d/nix.sh`.
 
 ### Linux
 
-```console
-sudo rm -rf /etc/profile/nix.sh /etc/nix /nix ~root/.nix-profile ~root/.nix-defexpr ~root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
+If you are on Linux with systemd:
 
-# If you are on Linux with systemd, you will need to run:
-sudo systemctl stop nix-daemon.socket
-sudo systemctl stop nix-daemon.service
-sudo systemctl disable nix-daemon.socket
-sudo systemctl disable nix-daemon.service
-sudo systemctl daemon-reload
+1. Remove the Nix daemon service:
+
+   ```console
+   sudo systemctl stop nix-daemon.service
+   sudo systemctl disable nix-daemon.socket nix-daemon.service
+   sudo systemctl daemon-reload
+   ```
+
+1. Remove systemd service files:
+
+   ```console
+   sudo rm /etc/systemd/system/nix-daemon.service /etc/systemd/system/nix-daemon.socket
+   ```
+
+1. The installer script uses systemd-tmpfiles to create the socket directory.
+    You may also want to remove the configuration for that:
+
+   ```console
+   sudo rm /etc/tmpfiles.d/nix-daemon.conf
+   ```
+
+Remove files created by Nix:
+
+```console
+sudo rm -rf /nix /etc/nix /etc/profile/nix.sh ~root/.nix-profile ~root/.nix-defexpr ~root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
 ```
 
-There may also be references to Nix in `/etc/profile`, `/etc/bashrc`,
-and `/etc/zshrc` which you may remove.
+Remove build users and their group:
+
+```console
+for i in $(seq 1 32); do
+  sudo userdel nixbld$i
+done
+sudo groupdel nixbld
+```
+
+There may also be references to Nix in
+
+- `/etc/profile`
+- `/etc/bashrc`
+- `/etc/zshrc`
+
+which you may remove.
 
 ### macOS
 

doc/manual/src/introduction.md

@@ -104,7 +104,7 @@ a currently running program.
 
 Packages are built from _Nix expressions_, which is a simple
 functional language.  A Nix expression describes everything that goes
-into a package build action (a “derivation”): other packages, sources,
+into a package build task (a “derivation”): other packages, sources,
 the build script, environment variables for the build script, etc.
 Nix tries very hard to ensure that Nix expressions are
 _deterministic_: building a Nix expression twice should yield the same

doc/manual/src/language/derivations.md

@@ -1,7 +1,7 @@
 # Derivations
 
 The most important built-in function is `derivation`, which is used to
-describe a single derivation (a build action). It takes as input a set,
+describe a single derivation (a build task). It takes as input a set,
 the attributes of which specify the inputs of the build.
 
   - There must be an attribute named [`system`]{#attr-system} whose value must be a

doc/manual/src/language/index.md

@@ -31,3 +31,551 @@ The Nix language is
 
   Type errors are only detected when expressions are evaluated.
 
+# Overview
+
+This is an incomplete overview of language features, by example.
+
+<table>
+ <tr>
+  <th>
+   Example
+  </th>
+  <th>
+   Description
+  </th>
+ </tr>
+ <tr>
+  <td>
+
+
+   *Basic values*
+
+
+  </td>
+  <td>
+
+
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `"hello world"`
+
+  </td>
+  <td>
+
+   A string
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   ```
+   ''
+     multi
+      line
+       string
+   ''
+   ```
+
+  </td>
+  <td>
+
+   A multi-line string. Strips common prefixed whitespace. Evaluates to `"multi\n line\n  string"`.
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `"hello ${ { a = "world" }.a }"`
+
+   `"1 2 ${toString 3}"`
+
+   `"${pkgs.bash}/bin/sh"`
+
+  </td>
+  <td>
+
+   String interpolation (expands to `"hello world"`, `"1 2 3"`, `"/nix/store/<hash>-bash-<version>/bin/sh"`)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `true`, `false`
+
+  </td>
+  <td>
+
+   Booleans
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `null`
+
+  </td>
+  <td>
+
+   Null value
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `123`
+
+  </td>
+  <td>
+
+   An integer
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `3.141`
+
+  </td>
+  <td>
+
+   A floating point number
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `/etc`
+
+  </td>
+  <td>
+
+   An absolute path
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `./foo.png`
+
+  </td>
+  <td>
+
+   A path relative to the file containing this Nix expression
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `~/.config`
+
+  </td>
+  <td>
+
+   A home path. Evaluates to the `"<user's home directory>/.config"`.
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   <nixpkgs>
+
+  </td>
+  <td>
+
+   Search path. Value determined by [`$NIX_PATH` environment variable](../command-ref/env-common.md#env-NIX_PATH).
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   *Compound values*
+
+  </td>
+  <td>
+
+
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ x = 1; y = 2; }`
+
+  </td>
+  <td>
+
+   A set with attributes named `x` and `y`
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ foo.bar = 1; }`
+
+  </td>
+  <td>
+
+   A nested set, equivalent to `{ foo = { bar = 1; }; }`
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `rec { x = "foo"; y = x + "bar"; }`
+
+  </td>
+  <td>
+
+   A recursive set, equivalent to `{ x = "foo"; y = "foobar"; }`
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `[ "foo" "bar" "baz" ]`
+
+   `[ 1 2 3 ]`
+
+   `[ (f 1) { a = 1; b = 2; } [ "c" ] ]`
+
+  </td>
+  <td>
+
+   Lists with three elements.
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   *Operators*
+
+  </td>
+  <td>
+
+
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `"foo" + "bar"`
+
+  </td>
+  <td>
+
+   String concatenation
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `1 + 2`
+
+  </td>
+  <td>
+
+   Integer addition
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `"foo" == "f" + "oo"`
+
+  </td>
+  <td>
+
+   Equality test (evaluates to `true`)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `"foo" != "bar"`
+
+  </td>
+  <td>
+
+   Inequality test (evaluates to `true`)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `!true`
+
+  </td>
+  <td>
+
+   Boolean negation
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ x = 1; y = 2; }.x`
+
+  </td>
+  <td>
+
+   Attribute selection (evaluates to `1`)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ x = 1; y = 2; }.z or 3`
+
+  </td>
+  <td>
+
+   Attribute selection with default (evaluates to `3`)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ x = 1; y = 2; } // { z = 3; }`
+
+  </td>
+  <td>
+
+   Merge two sets (attributes in the right-hand set taking precedence)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   *Control structures*
+
+  </td>
+  <td>
+
+
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `if 1 + 1 == 2 then "yes!" else "no!"`
+
+  </td>
+  <td>
+
+   Conditional expression
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `assert 1 + 1 == 2; "yes!"`
+
+  </td>
+  <td>
+
+   Assertion check (evaluates to `"yes!"`).
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `let x = "foo"; y = "bar"; in x + y`
+
+  </td>
+  <td>
+
+   Variable definition
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `with builtins; head [ 1 2 3 ]`
+
+  </td>
+  <td>
+
+   Add all attributes from the given set to the scope (evaluates to `1`)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   *Functions (lambdas)*
+
+  </td>
+  <td>
+
+
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `x: x + 1`
+
+  </td>
+  <td>
+
+   A function that expects an integer and returns it increased by 1
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `x: y: x + y`
+
+  </td>
+  <td>
+
+   Curried function, equivalent to `x: (y: x + y)`. Can be used like a function that takes two arguments and returns their sum.
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `(x: x + 1) 100`
+
+  </td>
+  <td>
+
+   A function call (evaluates to 101)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `let inc = x: x + 1; in inc (inc (inc 100))`
+
+  </td>
+  <td>
+
+   A function bound to a variable and subsequently called by name (evaluates to 103)
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ x, y }: x + y`
+
+  </td>
+  <td>
+
+   A function that expects a set with required attributes `x` and `y` and concatenates them
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ x, y ? "bar" }: x + y`
+
+  </td>
+  <td>
+
+   A function that expects a set with required attribute `x` and optional `y`, using `"bar"` as default value for `y`
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ x, y, ... }: x + y`
+
+  </td>
+  <td>
+
+   A function that expects a set with required attributes `x` and `y` and ignores any other attributes
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `{ x, y } @ args: x + y`
+
+   `args @ { x, y }: x + y`
+
+  </td>
+  <td>
+
+   A function that expects a set with required attributes `x` and `y`, and binds the whole set to `args`
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   *Built-in functions*
+
+  </td>
+  <td>
+
+
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `import ./foo.nix`
+
+  </td>
+  <td>
+
+   Load and return Nix expression in given file
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `map (x: x + x) [ 1 2 3 ]`
+
+  </td>
+  <td>
+
+   Apply a function to every element of a list (evaluates to `[ 2 4 6 ]`)
+
+  </td>
+ </tr>
+</table>

doc/manual/src/language/operators.md

@@ -1,28 +1,167 @@
 # Operators
 
-The table below lists the operators in the Nix language, in
-order of precedence (from strongest to weakest binding).
+| Name                                   | Syntax                                     | Associativity | Precedence |
+|----------------------------------------|--------------------------------------------|---------------|------------|
+| [Attribute selection]                  | *attrset* `.` *attrpath* \[ `or` *expr* \] | none          | 1          |
+| Function application                   | *func* *expr*                              | left          | 2          |
+| [Arithmetic negation][arithmetic]      | `-` *number*                               | none          | 3          |
+| [Has attribute]                        | *attrset* `?` *attrpath*                   | none          | 4          |
+| List concatenation                     | *list* `++` *list*                         | right         | 5          |
+| [Multiplication][arithmetic]           | *number* `*` *number*                      | left          | 6          |
+| [Division][arithmetic]                 | *number* `/` *number*                      | left          | 6          |
+| [Subtraction][arithmetic]              | *number* `-` *number*                      | left          | 7          |
+| [Addition][arithmetic]                 | *number* `+` *number*                      | left          | 7          |
+| [String concatenation]                 | *string* `+` *string*                      | left          | 7          |
+| [Path concatenation]                   | *path* `+` *path*                          | left          | 7          |
+| [Path and string concatenation]        | *path* `+` *string*                        | left          | 7          |
+| [String and path concatenation]        | *string* `+` *path*                        | left          | 7          |
+| Logical negation (`NOT`)               | `!` *bool*                                 | none          | 8          |
+| [Update]                               | *attrset* `//` *attrset*                   | right         | 9          |
+| [Less than][Comparison]                | *expr* `<` *expr*                          | none          | 10         |
+| [Less than or equal to][Comparison]    | *expr* `<=` *expr*                         | none          | 10         |
+| [Greater than][Comparison]             | *expr* `>` *expr*                          | none          | 10         |
+| [Greater than or equal to][Comparison] | *expr* `>=` *expr*                         | none          | 10         |
+| [Equality]                             | *expr* `==` *expr*                         | none          | 11         |
+| Inequality                             | *expr* `!=` *expr*                         | none          | 11         |
+| Logical conjunction (`AND`)            | *bool* `&&` *bool*                         | left          | 12         |
+| Logical disjunction (`OR`)             | *bool* `||` *bool*                         | left          | 13         |
+| [Logical implication]                  | *bool* `->` *bool*                         | none          | 14         |
+
+[string]: ./values.md#type-string
+[path]: ./values.md#type-path
+[number]: ./values.md#type-number
+[list]: ./values.md#list
+[attribute set]: ./values.md#attribute-set
+
+## Attribute selection
+
+Select the attribute denoted by attribute path *attrpath* from [attribute set] *attrset*.
+If the attribute doesn’t exist, return *value* 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.
+An attribute name can be an identifier or a string.
+
+> *attrpath* = *name* [ `.` *name* ]...
+> *name* = *identifier* | *string*
+> *identifier* ~ `[a-zA-Z_][a-zA-Z0-9_'-]*`
+
+[Attribute selection]: #attribute-selection
+
+## Has attribute
+
+> *attrset* `?` *attrpath*
+
+Test whether [attribute set] *attrset* contains the attribute denoted by *attrpath*.
+The result is a [Boolean] value.
+
+[Boolean]: ./values.md#type-boolean
+
+[Has attribute]: #has-attribute
+
+## Arithmetic
+
+Numbers are type-compatible:
+Pure integer operations will always return integers, whereas any operation involving at least one floating point number return a floating point number.
+
+See also [Comparison] and [Equality].
+
+The `+` operator is overloaded to also work on strings and paths.
+
+[arithmetic]: #arithmetic
+
+## String concatenation
+
+> *string* `+` *string*
+
+Concatenate two [string]s and merge their string contexts.
+
+[String concatenation]: #string-concatenation
+
+## Path concatenation
+
+> *path* `+` *path*
+
+Concatenate two [path]s.
+The result is a path.
+
+[Path concatenation]: #path-concatenation
+
+## Path and string concatenation
+
+> *path* + *string*
+
+Concatenate *[path]* with *[string]*.
+The result is a path.
+
+> **Note**
+>
+> The string must not have a string context that refers to a [store path].
+
+[Path and string concatenation]: #path-and-string-concatenation
+
+## String and path concatenation
+
+> *string* + *path*
+
+Concatenate *[string]* with *[path]*.
+The result is a string.
+
+> **Important**
+>
+> The file or directory at *path* must exist and is copied to the [store].
+> The path appears in the result as the corresponding [store path].
+
+[store path]: ../glossary.md#gloss-store-path
+[store]: ../glossary.md#gloss-store
+
+[Path and string concatenation]: #path-and-string-concatenation
+
+## Update
+
+> *attrset1* + *attrset2*
+
+Update [attribute set] *attrset1* with names and values from *attrset2*.
+
+The returned attribute set will have of all the attributes in *e1* and *e2*.
+If an attribute name is present in both, the attribute value from the former is taken.
+
+[Update]: #update
+
+## Comparison
+
+Comparison is
+
+- [arithmetic] for [number]s 
+- lexicographic for [string]s and [path]s
+- item-wise lexicographic for [list]s:
+  elements at the same index in both lists are compared according to their type and skipped if they are equal.
+
+All comparison operators are implemented in terms of `<`, and the following equivalencies hold:
+
+| comparison   | implementation        |
+|--------------|-----------------------|
+| *a* `<=` *b* | `! (` *b* `<` *a* `)` |
+| *a* `>`  *b* |       *b* `<` *a*     |
+| *a* `>=` *b* | `! (` *a* `<` *b* `)` |
+
+[Comparison]: #comparison-operators
+
+## Equality
+
+- [Attribute sets][attribute set] and [list]s are compared recursively, and therefore are fully evaluated.
+- Comparison of [function]s always returns `false`.
+- Numbers are type-compatible, see [arithmetic] operators.
+- Floating point numbers only differ up to a limited precision.
+
+[function]: ./constructs.md#functions
+
+[Equality]: #equality
+
+## Logical implication
+
+Equivalent to `!`*b1* `||` *b2*.
+
+[Logical implication]: #logical-implication
 
-| Name                     | Syntax                              | Associativity | Description                                                                                                                                                                                                                   | Precedence |
-| ------------------------ | ----------------------------------- | ------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------- |
-| Select                   | *e* `.` *attrpath* \[ `or` *def* \] | none          | Select attribute denoted by the attribute path *attrpath* from set *e*. (An attribute path is a dot-separated list of attribute names.) If the attribute doesn’t exist, return *def* if provided, otherwise abort evaluation. | 1          |
-| Application              | *e1* *e2*                           | left          | Call function *e1* with argument *e2*.                                                                                                                                                                                        | 2          |
-| Arithmetic Negation      | `-` *e*                             | none          | Arithmetic negation.                                                                                                                                                                                                          | 3          |
-| Has Attribute            | *e* `?` *attrpath*                  | none          | Test whether set *e* contains the attribute denoted by *attrpath*; return `true` or `false`.                                                                                                                                  | 4          |
-| List Concatenation       | *e1* `++` *e2*                      | right         | List concatenation.                                                                                                                                                                                                           | 5          |
-| Multiplication           | *e1* `*` *e2*,                      | left          | Arithmetic multiplication.                                                                                                                                                                                                    | 6          |
-| Division                 | *e1* `/` *e2*                       | left          | Arithmetic division.                                                                                                                                                                                                          | 6          |
-| Addition                 | *e1* `+` *e2*                       | left          | Arithmetic addition.                                                                                                                                                                                                          | 7          |
-| Subtraction              | *e1* `-` *e2*                       | left          | Arithmetic subtraction.                                                                                                                                                                                                       | 7          |
-| String Concatenation     | *string1* `+` *string2*             | left          | String concatenation.                                                                                                                                                                                                         | 7          |
-| Not                      | `!` *e*                             | none          | Boolean negation.                                                                                                                                                                                                             | 8          |
-| Update                   | *e1* `//` *e2*                      | right         | Return a set consisting of the attributes in *e1* and *e2* (with the latter taking precedence over the former in case of equally named attributes).                                                                           | 9          |
-| Less Than                | *e1* `<` *e2*,                      | none          | Arithmetic/lexicographic comparison.                                                                                                                                                                                                        | 10         |
-| Less Than or Equal To    | *e1* `<=` *e2*                      | none          | Arithmetic/lexicographic comparison.                                                                                                                                                                                                        | 10         |
-| Greater Than             | *e1* `>` *e2*                       | none          | Arithmetic/lexicographic comparison.                                                                                                                                                                                                        | 10         |
-| Greater Than or Equal To | *e1* `>=` *e2*                      | none          | Arithmetic/lexicographic comparison.                                                                                                                                                                                                        | 10         |
-| Equality                 | *e1* `==` *e2*                      | none          | Equality.                                                                                                                                                                                                                     | 11         |
-| Inequality               | *e1* `!=` *e2*                      | none          | Inequality.                                                                                                                                                                                                                   | 11         |
-| Logical AND              | *e1* `&&` *e2*                      | left          | Logical AND.                                                                                                                                                                                                                  | 12         |
-| Logical OR               | *e1* <code>&#124;&#124;</code> *e2* | left          | Logical OR.                                                                                                                                                                                                                   | 13         |
-| Logical Implication      | *e1* `->` *e2*                      | none          | Logical implication (equivalent to <code>!e1 &#124;&#124; e2</code>).                                                                                                                                                                            | 14         |

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

@@ -0,0 +1,82 @@
+# String interpolation
+
+String interpolation is a language feature where a [string], [path], or [attribute name] can contain expressions enclosed in `${ }` (dollar-sign with curly brackets).
+
+Such a string is an *interpolated string*, and an expression inside is an *interpolated expression*.
+
+Interpolated expressions must evaluate to one of the following:
+
+- a [string]
+- a [path]
+- a [derivation]
+
+[string]: ./values.md#type-string
+[path]: ./values.md#type-path
+[attribute name]: ./values.md#attribute-set
+[derivation]: ../glossary.md#gloss-derivation
+
+## Examples
+
+### String
+
+Rather than writing
+
+```nix
+"--with-freetype2-library=" + freetype + "/lib"
+```
+
+(where `freetype` is a [derivation]), you can instead write
+
+```nix
+"--with-freetype2-library=${freetype}/lib"
+```
+
+The latter is automatically translated to the former.
+
+A more complicated example (from the Nix expression for [Qt](http://www.trolltech.com/products/qt)):
+
+```nix
+configureFlags = "
+  -system-zlib -system-libpng -system-libjpeg
+  ${if openglSupport then "-dlopen-opengl
+    -L${mesa}/lib -I${mesa}/include
+    -L${libXmu}/lib -I${libXmu}/include" else ""}
+  ${if threadSupport then "-thread" else "-no-thread"}
+";
+```
+
+Note that Nix expressions and strings can be arbitrarily nested;
+in this case the outer string contains various interpolated expressions that themselves contain strings (e.g., `"-thread"`), some of which in turn contain interpolated expressions (e.g., `${mesa}`).
+
+### Path
+
+Rather than writing
+
+```nix
+./. + "/" + foo + "-" + bar + ".nix"
+```
+
+or
+
+```nix
+./. + "/${foo}-${bar}.nix"
+```
+
+you can instead write
+
+```nix
+./${foo}-${bar}.nix
+```
+
+### Attribute name
+
+Attribute names can be created dynamically with string interpolation:
+
+```nix
+let name = "foo"; in
+{
+  ${name} = "bar";
+}
+```
+
+    { foo = "bar"; }

doc/manual/src/language/values.md

@@ -13,41 +13,9 @@
   returns and tabs can be written as `\n`, `\r` and `\t`,
   respectively.
 
-  You can include the result of an expression into a string by
-  enclosing it in `${...}`, a feature known as *antiquotation*. The
-  enclosed expression must evaluate to something that can be coerced
-  into a string (meaning that it must be a string, a path, or a
-  derivation). For instance, rather than writing
+  You can include the results of other expressions into a string by enclosing them in `${ }`, a feature known as [string interpolation].
 
-  ```nix
-  "--with-freetype2-library=" + freetype + "/lib"
-  ```
-
-  (where `freetype` is a derivation), you can instead write the more
-  natural
-
-  ```nix
-  "--with-freetype2-library=${freetype}/lib"
-  ```
-
-  The latter is automatically translated to the former. A more
-  complicated example (from the Nix expression for
-  [Qt](http://www.trolltech.com/products/qt)):
-
-  ```nix
-  configureFlags = "
-    -system-zlib -system-libpng -system-libjpeg
-    ${if openglSupport then "-dlopen-opengl
-      -L${mesa}/lib -I${mesa}/include
-      -L${libXmu}/lib -I${libXmu}/include" else ""}
-    ${if threadSupport then "-thread" else "-no-thread"}
-  ";
-  ```
-
-  Note that Nix expressions and strings can be arbitrarily nested; in
-  this case the outer string contains various antiquotations that
-  themselves contain strings (e.g., `"-thread"`), some of which in
-  turn contain expressions (e.g., `${mesa}`).
+  [string interpolation]: ./string-interpolation.md
 
   The second way to write string literals is as an *indented string*,
   which is enclosed between pairs of *double single-quotes*, like so:
@@ -75,7 +43,7 @@
   Note that the whitespace and newline following the opening `''` is
   ignored if there is no non-whitespace text on the initial line.
 
-  Antiquotation (`${expr}`) is supported in indented strings.
+  Indented strings support [string interpolation].
 
   Since `${` and `''` have special meaning in indented strings, you
   need a way to quote them. `$` can be escaped by prefixing it with
@@ -117,9 +85,10 @@
   Numbers, which can be *integers* (like `123`) or *floating point*
   (like `123.43` or `.27e13`).
 
-  Numbers are type-compatible: pure integer operations will always
-  return integers, whereas any operation involving at least one
-  floating point number will have a floating point number as a result.
+  See [arithmetic] and [comparison] operators for semantics.
+
+  [arithmetic]: ./operators.md#arithmetic
+  [comparison]: ./operators.md#comparison
 
 - <a id="type-path" href="#type-path">Path</a>
 
@@ -143,12 +112,23 @@
   environment variable `NIX_PATH` will be searched for the given file
   or directory name.
 
-  Antiquotation is supported in any paths except those in angle brackets.
-  `./${foo}-${bar}.nix` is a more convenient way of writing
-  `./. + "/" + foo + "-" + bar + ".nix"` or `./. + "/${foo}-${bar}.nix"`. At
-  least one slash must appear *before* any antiquotations for this to be
-  recognized as a path. `a.${foo}/b.${bar}` is a syntactically valid division
-  operation. `./a.${foo}/b.${bar}` is a path.
+  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 `"${./foo.txt}"` will cause `foo.txt` in the current directory to be copied into the Nix store and result in the string `"/nix/store/<hash>-foo.txt"`.
+
+  Note that the Nix language assumes that all input files will remain _unchanged_ while  evaluating a Nix expression.
+  For example, assume you used a file path in an interpolated string during a `nix repl` session.
+  Later in the same session, after having changed the file contents, evaluating the interpolated string with the file path again might not return a new store path, since Nix might not re-read the file contents.
+
+  Paths themselves, except those in angle brackets (`< >`), support [string interpolation].
+
+  At least one slash (`/`) must appear *before* any interpolated expression for the result to be recognized as a path.
+
+  `a.${foo}/b.${bar}` is a syntactically valid division operation.
+  `./a.${foo}/b.${bar}` is a path.
 
 - <a id="type-boolean" href="#type-boolean">Boolean</a>
 
@@ -221,23 +201,33 @@ will evaluate to `"Xyzzy"` because there is no `c` attribute in the set.
 You can use arbitrary double-quoted strings as attribute names:
 
 ```nix
-{ "foo ${bar}" = 123; "nix-1.0" = 456; }."foo ${bar}"
+{ "$!@#?" = 123; }."$!@#?"
 ```
 
-This will evaluate to `123` (Assuming `bar` is antiquotable). In the
-case where an attribute name is just a single antiquotation, the quotes
-can be dropped:
-
 ```nix
-{ foo = 123; }.${bar} or 456
+let bar = "bar";
+{ "foo ${bar}" = 123; }."foo ${bar}"
 ```
 
-This will evaluate to `123` if `bar` evaluates to `"foo"` when coerced
-to a string and `456` otherwise (again assuming `bar` is antiquotable).
+Both will evaluate to `123`.
+
+Attribute names support [string interpolation]:
+
+```nix
+let bar = "foo"; in
+{ foo = 123; }.${bar}
+```
+
+```nix
+let bar = "foo"; in
+{ ${bar} = 123; }.foo
+```
+
+Both will evaluate to `123`.
 
 In the special case where an attribute name inside of a set declaration
-evaluates to `null` (which is normally an error, as `null` is not
-antiquotable), that attribute is simply not added to the set:
+evaluates to `null` (which is normally an error, as `null` cannot be coerced to
+a string), that attribute is simply not added to the set:
 
 ```nix
 { ${if foo then "bar" else null} = true; }

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

@@ -0,0 +1,43 @@
+# Release 2.12 (2022-12-06)
+
+* 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].
+
+  [nspawn]: https://github.com/NixOS/nix/blob/67bcb99700a0da1395fa063d7c6586740b304598/tests/systemd-nspawn.nix.
+
+  A build can enable this by setting the derivation attribute:
+
+  ```
+  requiredSystemFeatures = [ "uid-range" ];
+  ```
+
+  The `uid-range` [system feature] requires the [`auto-allocate-uids`]
+  setting to be enabled.
+
+  [system feature]: ../command-ref/conf-file.md#conf-system-features
+
+* Nix can now automatically pick UIDs for builds, removing the need to
+  create `nixbld*` user accounts. See [`auto-allocate-uids`].
+
+  [`auto-allocate-uids`]: ../command-ref/conf-file.md#conf-auto-allocate-uids
+
+* On Linux, Nix has experimental support for running builds inside a
+  cgroup. See
+  [`use-cgroups`](../command-ref/conf-file.md#conf-use-cgroups).
+
+* `<nix/fetchurl.nix>` now accepts an additional argument `impure` which
+  defaults to `false`.  If it is set to `true`, the `hash` and `sha256`
+  arguments will be ignored and the resulting derivation will have
+  `__impure` set to `true`, making it an impure derivation.
+
+* If `builtins.readFile` is called on a file with context, then only
+  the parts of the context that appear in the content of the file are
+  retained.  This avoids a lot of spurious errors where strings end up
+  having a context just because they are read from a store path
+  ([#7260](https://github.com/NixOS/nix/pull/7260)).
+
+* `nix build --json` now prints some statistics about top-level
+  derivations, such as CPU statistics when cgroups are enabled.

doc/manual/src/release-notes/rl-2.13.md

@@ -0,0 +1,40 @@
+# Release 2.13 (2023-01-17)
+
+* The `repeat` and `enforce-determinism` options have been removed
+  since they had been broken under many circumstances for a long time.
+
+* You can now use [flake references] in the [old command line interface], e.g.
+
+   [flake references]: ../command-ref/new-cli/nix3-flake.md#flake-references
+   [old command line interface]: ../command-ref/main-commands.md
+
+  ```shell-session
+  # nix-build flake:nixpkgs -A hello
+  # nix-build -I nixpkgs=flake:github:NixOS/nixpkgs/nixos-22.05 \
+      '<nixpkgs>' -A hello
+  # NIX_PATH=nixpkgs=flake:nixpkgs nix-build '<nixpkgs>' -A hello
+  ```
+
+* Instead of "antiquotation", the more common term [string interpolation](../language/string-interpolation.md) is now used consistently.
+  Historical release notes were not changed.
+
+* Allow explicitly selecting outputs in a store derivation installable, just like we can do with other sorts of installables.
+  For example,
+  ```shell-session
+  # nix build /nix/store/gzaflydcr6sb3567hap9q6srzx8ggdgg-glibc-2.33-78.drv^dev
+  ```
+  now works just as
+  ```shell-session
+  # nix build nixpkgs#glibc^dev
+  ```
+  does already.
+
+* On Linux, `nix develop` now sets the
+  [*personality*](https://man7.org/linux/man-pages/man2/personality.2.html)
+  for the development shell in the same way as the actual build of the
+  derivation. This makes shells for `i686-linux` derivations work
+  correctly on `x86_64-linux`.
+
+* You can now disable the global flake registry by setting the `flake-registry`
+  configuration option to an empty string. The same can be achieved at runtime with
+  `--flake-registry ""`.

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

@@ -1,7 +1,2 @@
 # Release X.Y (202?-??-??)
 
-* `<nix/fetchurl.nix>` now accepts an additional argument `impure` which
-  defaults to `false`.  If it is set to `true`, the `hash` and `sha256`
-  arguments will be ignored and the resulting derivation will have
-  `__impure` set to `true`, making it an impure derivation.
-

docker.nix

@@ -36,6 +36,17 @@ let
       shell = "${pkgs.bashInteractive}/bin/bash";
       home = "/root";
       gid = 0;
+      groups = [ "root" ];
+      description = "System administrator";
+    };
+
+    nobody = {
+      uid = 65534;
+      shell = "${pkgs.shadow}/bin/nologin";
+      home = "/var/empty";
+      gid = 65534;
+      groups = [ "nobody" ];
+      description = "Unprivileged account (don't use!)";
     };
 
   } // lib.listToAttrs (
@@ -57,6 +68,7 @@ let
   groups = {
     root.gid = 0;
     nixbld.gid = 30000;
+    nobody.gid = 65534;
   };
 
   userToPasswd = (

flake.lock

@@ -18,16 +18,16 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1657693803,
-        "narHash": "sha256-G++2CJ9u0E7NNTAi9n5G8TdDmGJXcIjkJ3NF8cetQB8=",
+        "lastModified": 1670461440,
+        "narHash": "sha256-jy1LB8HOMKGJEGXgzFRLDU1CBGL0/LlkolgnqIsF0D8=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "365e1b3a859281cf11b94f87231adeabbdd878a2",
+        "rev": "04a75b2eecc0acf6239acf9dd04485ff8d14f425",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
-        "ref": "nixos-22.05-small",
+        "ref": "nixos-22.11-small",
         "repo": "nixpkgs",
         "type": "github"
       }

flake.nix

@@ -1,7 +1,7 @@
 {
   description = "The purely functional package manager";
 
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.05-small";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.11-small";
   inputs.nixpkgs-regression.url = "github:NixOS/nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
   inputs.lowdown-src = { url = "github:kristapsdz/lowdown"; flake = false; };
 
@@ -9,14 +9,14 @@
 
     let
 
-      version = builtins.readFile ./.version + versionSuffix;
+      officialRelease = true;
+
+      version = nixpkgs.lib.fileContents ./.version + versionSuffix;
       versionSuffix =
         if officialRelease
         then ""
         else "pre${builtins.substring 0 8 (self.lastModifiedDate or self.lastModified or "19700101")}_${self.shortRev or "dirty"}";
 
-      officialRelease = false;
-
       linux64BitSystems = [ "x86_64-linux" "aarch64-linux" ];
       linuxSystems = linux64BitSystems ++ [ "i686-linux" ];
       systems = linuxSystems ++ [ "x86_64-darwin" "aarch64-darwin" ];
@@ -96,6 +96,7 @@
             buildPackages.flex
             (lib.getBin buildPackages.lowdown-nix)
             buildPackages.mdbook
+            buildPackages.mdbook-linkcheck
             buildPackages.autoconf-archive
             buildPackages.autoreconfHook
             buildPackages.pkg-config
@@ -108,7 +109,7 @@
           ++ lib.optionals stdenv.hostPlatform.isLinux [(buildPackages.util-linuxMinimal or buildPackages.utillinuxMinimal)];
 
         buildDeps =
-          [ (curl.override { patchNetrcRegression = true; })
+          [ curl
             bzip2 xz brotli editline
             openssl sqlite
             libarchive
@@ -133,7 +134,8 @@
               patches = (o.patches or []) ++ [
                 ./boehmgc-coroutine-sp-fallback.diff
               ];
-            }))
+            })
+            )
             nlohmann_json
           ];
       };
@@ -364,7 +366,7 @@
 
               buildInputs =
                 [ nix
-                  (curl.override { patchNetrcRegression = true; })
+                  curl
                   bzip2
                   xz
                   pkgs.perl
@@ -420,6 +422,8 @@
         buildCross = nixpkgs.lib.genAttrs crossSystems (crossSystem:
           nixpkgs.lib.genAttrs ["x86_64-linux"] (system: self.packages.${system}."nix-${crossSystem}"));
 
+        buildNoGc = nixpkgs.lib.genAttrs systems (system: self.packages.${system}.nix.overrideAttrs (a: { configureFlags = (a.configureFlags or []) ++ ["--enable-gc=no"];}));
+
         # Perl bindings for various platforms.
         perlBindings = nixpkgs.lib.genAttrs systems (system: self.packages.${system}.nix.perl-bindings);
 
@@ -506,6 +510,12 @@
           overlay = self.overlays.default;
         });
 
+        tests.containers = (import ./tests/containers.nix rec {
+          system = "x86_64-linux";
+          inherit nixpkgs;
+          overlay = self.overlays.default;
+        });
+
         tests.setuid = nixpkgs.lib.genAttrs
           ["i686-linux" "x86_64-linux"]
           (system:
@@ -527,6 +537,12 @@
               mkdir $out
             '';
 
+        tests.nixpkgsLibTests =
+          nixpkgs.lib.genAttrs systems (system:
+            import (nixpkgs + "/lib/tests/release.nix")
+              { pkgs = nixpkgsFor.${system}; }
+          );
+
         metrics.nixpkgs = import "${nixpkgs-regression}/pkgs/top-level/metrics.nix" {
           pkgs = nixpkgsFor.x86_64-linux;
           nixpkgs = nixpkgs-regression;
@@ -557,6 +573,7 @@
         binaryTarball = self.hydraJobs.binaryTarball.${system};
         perlBindings = self.hydraJobs.perlBindings.${system};
         installTests = self.hydraJobs.installTests.${system};
+        nixpkgsLibTests = self.hydraJobs.tests.nixpkgsLibTests.${system};
       } // (nixpkgs.lib.optionalAttrs (builtins.elem system linux64BitSystems)) {
         dockerImage = self.hydraJobs.dockerImage.${system};
       });

maintainers/README.md

@@ -0,0 +1,107 @@
+# Nix maintainers team
+
+## Motivation
+
+The goal of the team is to help other people to contribute to Nix.
+
+## Members
+
+- Eelco Dolstra (@edolstra) – Team lead
+- Théophane Hufschmitt (@thufschmitt)
+- Valentin Gagarin (@fricklerhandwerk)
+- Thomas Bereknyei (@tomberek)
+- Robert Hensing (@roberth)
+
+## Meeting protocol
+
+The team meets twice a week:
+
+- Discussion meeting: [Fridays 13:00-14:00 CET](https://calendar.google.com/calendar/event?eid=MHNtOGVuNWtrZXNpZHR2bW1sM3QyN2ZjaGNfMjAyMjExMjVUMTIwMDAwWiBiOW81MmZvYnFqYWs4b3E4bGZraGczdDBxZ0Bn)
+
+  1. Triage issues and pull requests from the _No Status_ column (30 min)
+  2. Discuss issues and pull requests from the _To discuss_ column (30 min)
+
+- Work meeting: [Mondays 13:00-15:00 CET](https://calendar.google.com/calendar/event?eid=NTM1MG1wNGJnOGpmOTZhYms3bTB1bnY5cWxfMjAyMjExMjFUMTIwMDAwWiBiOW81MmZvYnFqYWs4b3E4bGZraGczdDBxZ0Bn)
+
+  1. Code review on pull requests from _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).
+
+## Project board protocol
+
+The team uses a [GitHub project board](https://github.com/orgs/NixOS/projects/19/views/1) for tracking its work.
+
+Issues on the board progress through the following states:
+
+- No Status
+
+  During the discussion meeting, the team triages new items.
+  To be considered, issues and pull requests must have a high-level description to provide the whole team with the necessary context at a glance.
+
+  On every meeting, at least one item from each of the following categories is inspected:
+
+  1. [critical](https://github.com/NixOS/nix/labels/critical)
+  2. [security](https://github.com/NixOS/nix/labels/security)
+  3. [regression](https://github.com/NixOS/nix/labels/regression)
+  4. [bug](https://github.com/NixOS/nix/issues?q=is%3Aopen+label%3Abug+sort%3Areactions-%2B1-desc)
+
+  - [oldest pull requests](https://github.com/NixOS/nix/pulls?q=is%3Apr+is%3Aopen+sort%3Acreated-asc)
+  - [most popular pull requests](https://github.com/NixOS/nix/pulls?q=is%3Apr+is%3Aopen+sort%3Areactions-%2B1-desc)
+  - [oldest issues](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Acreated-asc)
+  - [most popular issues](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc)
+
+  Team members can also add pull requests or issues they would like the whole team to consider.
+
+  If there is disagreement on the general idea behind an issue or pull request, it is moved to _To discuss_, otherwise to _In review_.
+
+- To discuss
+
+  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.
+
+  As a general guideline, the order of items is determined as follows:
+
+  - Prioritise pull requests over issues
+
+    Contributors who took the time to implement concrete change proposals should not wait indefinitely.
+
+  - Prioritise fixing bugs over documentation, improvements or new features
+
+    The team values stability and accessibility higher than raw functionality.
+
+  - Interleave issues and PRs
+
+    This way issues without attempts at a solution get a chance to get addressed.
+
+- In review
+
+  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.
+
+- Assigned for merging
+
+  One team member is assigned to each of these pull requests.
+  They will communicate with the authors, and make the final approval once all remaining issues are addressed.
+
+  If more substantive issues arise, the assignee can move the pull request back to _To discuss_ to involve the team again.
+
+The process is illustrated in the following diagram:
+
+```mermaid
+flowchart TD
+    discuss[To discuss]
+
+    review[To review]
+
+    New --> |Disagreement on idea| discuss
+    New & discuss --> |Consensus on idea| review
+
+    review --> |Consensus on implementation| Assigned
+
+    Assigned --> |Implementation issues arise| review
+    Assigned --> |Remaining issues fixed| Merged
+```

maintainers/upload-release.pl

@@ -115,10 +115,6 @@ sub downloadFile {
 
     write_file("$tmpFile.sha256", $sha256_actual);
 
-    if (! -e "$tmpFile.asc") {
-        system("gpg2 --detach-sign --armor $tmpFile") == 0 or die "unable to sign $tmpFile\n";
-    }
-
     return $sha256_expected;
 }
 
@@ -194,7 +190,7 @@ for my $fn (glob "$tmpDir/*") {
         my $configuration = ();
         $configuration->{content_type} = "application/octet-stream";
 
-        if ($fn =~ /.sha256|.asc|install/) {
+        if ($fn =~ /.sha256|install/) {
             # Text files
             $configuration->{content_type} = "text/plain";
         }

misc/launchd/org.nixos.nix-daemon.plist.in

@@ -28,7 +28,7 @@
     <key>SoftResourceLimits</key>
     <dict>
       <key>NumberOfFiles</key>
-      <integer>4096</integer>
+      <integer>1048576</integer>
     </dict>
   </dict>
 </plist>

misc/systemd/nix-daemon.service.in

@@ -9,7 +9,7 @@ ConditionPathIsReadWrite=@localstatedir@/nix/daemon-socket
 [Service]
 ExecStart=@@bindir@/nix-daemon nix-daemon --daemon
 KillMode=process
-LimitNOFILE=4096
+LimitNOFILE=1048576
 
 [Install]
 WantedBy=multi-user.target

mk/common-test.sh

@@ -0,0 +1,11 @@
+TESTS_ENVIRONMENT=("TEST_NAME=${test%.*}" 'NIX_REMOTE=')
+
+: ${BASH:=/usr/bin/env bash}
+
+init_test () {
+   cd tests && env "${TESTS_ENVIRONMENT[@]}" $BASH -e init.sh 2>/dev/null > /dev/null
+}
+
+run_test_proper () {
+   cd $(dirname $test) && env "${TESTS_ENVIRONMENT[@]}" $BASH -e $(basename $test)
+}

mk/debug-test.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+set -eu
+
+test=$1
+
+dir="$(dirname "${BASH_SOURCE[0]}")"
+source "$dir/common-test.sh"
+
+(init_test)
+run_test_proper

mk/run-test.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 set -u
 
@@ -7,7 +7,12 @@ green=""
 yellow=""
 normal=""
 
-post_run_msg="ran test $1..."
+test=$1
+
+dir="$(dirname "${BASH_SOURCE[0]}")"
+source "$dir/common-test.sh"
+
+post_run_msg="ran test $test..."
 if [ -t 1 ]; then
     red=""
     green=""
@@ -16,12 +21,12 @@ if [ -t 1 ]; then
 fi
 
 run_test () {
-    (cd tests && env ${TESTS_ENVIRONMENT} init.sh 2>/dev/null > /dev/null)
-    log="$(cd $(dirname $1) && env ${TESTS_ENVIRONMENT} $(basename $1) 2>&1)"
+    (init_test 2>/dev/null > /dev/null)
+    log="$(run_test_proper 2>&1)"
     status=$?
 }
 
-run_test "$1"
+run_test
 
 # Hack: Retry the test if it fails with “unexpected EOF reading a line” as these
 # appear randomly without anyone knowing why.
@@ -32,7 +37,7 @@ if [[ $status -ne 0 && $status -ne 99 && \
 ]]; then
     echo "$post_run_msg [${yellow}FAIL$normal] (possibly flaky, so will be retried)"
     echo "$log" | sed 's/^/    /'
-    run_test "$1"
+    run_test
 fi
 
 if [ $status -eq 0 ]; then

mk/tests.mk

@@ -8,7 +8,11 @@ define run-install-test
 
   .PHONY: $1.test
   $1.test: $1 $(test-deps)
-	@env TEST_NAME=$(basename $1) TESTS_ENVIRONMENT="$(tests-environment)" mk/run_test.sh $1 < /dev/null
+	@env BASH=$(bash) $(bash) mk/run-test.sh $1 < /dev/null
+
+  .PHONY: $1.test-debug
+  $1.test-debug: $1 $(test-deps)
+	@env BASH=$(bash) $(bash) mk/debug-test.sh $1 < /dev/null
 
 endef
 

roadmap.md

@@ -1,85 +0,0 @@
-# Nix is everywhere
-
-Nix is the universal build and [configuration management] tool.
-
-[configuration management]: https://www.sebokwiki.org/wiki/Configuration_Management
-
-Software developers use Nix as a matter of course every day, mostly without even noticing.
-Nix runs trivially, anywhere.
-
-For individuals to large organizations, Nix underpins the entire software supply chain:
-- Developer tooling
-- Build automation
-- Binary distribution
-
-To this end, the Nix team will work towards the following goals.
-
-## Make Nix easy to adopt
-
-  - Well-defined target user base
-      - anyone who wants to manage the complexity of - and build - software
-      - transform bits in a declarative and reproducible way
-  - Well-defined core user stories
-    - Ad hoc environments
-        - One-liner setup (nix-shell)
-    - Declarative environments
-        - One-liner setup ("templates")
-        - Easy modification/extension
-        - Easy and transparent usage ("direnv"/"lorri")
-    - Secret management as first-class citizen
-    - Configurations as first-class citizens
-        - Configuration/Modules/Nickel/etc.
-    - Language bindings
-    - Supply chain trust solution
-        - Content-addressed derivation
-        - Build result signing, key distribution
-        - SBOM/SLSA
-    - Unprivileged installation and use
-        <!-- valentin: this needs clarification, I still don't know what rewriting is -->
-        - Portable store?
-        - restricted-root
-        - ACLs
-        - rewriting
-    - ...
-  - Linux, MacOS and Windows support at feature parity
-
-## Make Nix a tool that users can rely on
-
-  - Reliable installer
-  - Effective testing
-    - Test coverage for all major use cases
-    - Memory safety validation (sanitizers, ...)
-    - Benchmarking infrastructure
-    - Test reports published and accessible
-  - Executable language specification
- 
-## Make Nix a good investment for users
-
-  - Explicit compatibility guarantees (and non-guarantees)
-    - Commitment to uncompromising reproducibility
-    - Well-defined release process
-    - Feature support status
-    - Deprecation strategy
-    - LTS commitments
-    - Close Flakes schism, remove uncertanity/ambiguity/confusion
-
-  - Exemplary contributor and maintainer experience
-    - Recommended development setup
-    - Testing guidance
-    - Formalize review criteria
-    - Formalize design criteria (technical invariants)
-    - Well-defined architecture of isolated components
-        - Swappable store
-          - Formalize store protocol
-        - Swappable Nix language evaluator
-        - Swappable scheduler and remote-build system
-            - Integrate Hydra (modulo UI) into Nix
-            - Remote protocol speed and reliability improvements
-            - Binary cache protocol speed improvements
-
-    - Minimal custom code base (proven off-the-shelf components where possible)
-      - Git file hashing
-      - Sandboxing, containers
-      - Capnproto for RPC
-      - Bazel RBE protocol
-      - ...

scripts/install-multi-user.sh

@@ -58,7 +58,7 @@ readonly EXTRACTED_NIX_PATH="$(dirname "$0")"
 
 readonly ROOT_HOME=~root
 
-if [ -t 0 ]; then
+if [ -t 0 ] && [ -z "${NIX_INSTALLER_YES:-}" ]; then
     readonly IS_HEADLESS='no'
 else
     readonly IS_HEADLESS='yes'
@@ -97,13 +97,10 @@ is_os_darwin() {
 }
 
 contact_us() {
-    echo "You can open an issue at https://github.com/nixos/nix/issues"
+    echo "You can open an issue at"
+    echo "https://github.com/NixOS/nix/issues/new?labels=installer&template=installer.md"
     echo ""
-    echo "Or feel free to contact the team:"
-    echo " - Matrix: #nix:nixos.org"
-    echo " - IRC: in #nixos on irc.libera.chat"
-    echo " - twitter: @nixos_org"
-    echo " - forum: https://discourse.nixos.org"
+    echo "Or get in touch with the community: https://nixos.org/community"
 }
 get_help() {
     echo "We'd love to help if you need it."
@@ -578,7 +575,7 @@ EOF
     # to extract _just_ the user's note, instead it is prefixed with
     # some plist junk. This was causing the user note to always be set,
     # even if there was no reason for it.
-    if ! poly_user_note_get "$username" | grep -q "Nix build user $coreid"; then
+    if poly_user_note_get "$username" | grep -q "Nix build user $coreid"; then
         row "              Note" "Nix build user $coreid"
     else
         poly_user_note_set "$username" "Nix build user $coreid"

scripts/install-nix-from-closure.sh

@@ -71,6 +71,8 @@ while [ $# -gt 0 ]; do
         #     # intentional tail space
         #     ACTIONS="${ACTIONS}uninstall "
         #     ;;
+        --yes)
+            export NIX_INSTALLER_YES=1;;
         --no-channel-add)
             export NIX_INSTALLER_NO_CHANNEL_ADD=1;;
         --daemon-user-count)
@@ -90,7 +92,7 @@ while [ $# -gt 0 ]; do
             shift;;
         *)
             {
-                echo "Nix Installer [--daemon|--no-daemon] [--daemon-user-count INT] [--no-channel-add] [--no-modify-profile] [--nix-extra-conf-file FILE]"
+                echo "Nix Installer [--daemon|--no-daemon] [--daemon-user-count INT] [--yes] [--no-channel-add] [--no-modify-profile] [--nix-extra-conf-file FILE]"
 
                 echo "Choose installation method."
                 echo ""
@@ -104,6 +106,8 @@ while [ $# -gt 0 ]; do
                 echo "              trivial to uninstall."
                 echo "              (default)"
                 echo ""
+                echo " --yes:               Run the script non-interactively, accepting all prompts."
+                echo ""
                 echo " --no-channel-add:    Don't add any channels. nixpkgs-unstable is installed by default."
                 echo ""
                 echo " --no-modify-profile: Don't modify the user profile to automatically load nix."

scripts/nix-profile-daemon.fish.in

@@ -1,3 +1,15 @@
+function add_path --argument-names new_path
+    if type -q fish_add_path
+        # fish 3.2.0 or newer
+	fish_add_path --prepend --global $new_path
+    else
+        # older versions of fish
+        if not contains $new_path $fish_user_paths
+            set --global fish_user_paths $new_path $fish_user_paths
+        end
+    end
+end
+
 # Only execute this file once per shell.
 if test -n "$__ETC_PROFILE_NIX_SOURCED"
   exit
@@ -31,5 +43,7 @@ else
   end
 end
 
-fish_add_path --prepend --global "@localstatedir@/nix/profiles/default/bin"
-fish_add_path --prepend --global "$HOME/.nix-profile/bin"
+add_path "@localstatedir@/nix/profiles/default/bin"
+add_path "$HOME/.nix-profile/bin"
+
+functions -e add_path

scripts/nix-profile.fish.in

@@ -1,3 +1,15 @@
+function add_path --argument-names new_path
+    if type -q fish_add_path
+        # fish 3.2.0 or newer
+	fish_add_path --prepend --global $new_path
+    else
+        # older versions of fish
+        if not contains $new_path $fish_user_paths
+            set --global fish_user_paths $new_path $fish_user_paths
+        end
+    end
+end
+
 if test -n "$HOME" && test -n "$USER"
 
     # Set up the per-user profile.
@@ -28,8 +40,12 @@ if test -n "$HOME" && test -n "$USER"
     # Only use MANPATH if it is already set. In general `man` will just simply
     # pick up `.nix-profile/share/man` because is it close to `.nix-profile/bin`
     # which is in the $PATH. For more info, run `manpath -d`.
-    set --export --prepend --path MANPATH "$NIX_LINK/share/man"
+    if set --query MANPATH
+      set --export --prepend --path MANPATH "$NIX_LINK/share/man"
+    end
 
-    fish_add_path --prepend --global "$NIX_LINK/bin"
+    add_path "$NIX_LINK/bin"
     set --erase NIX_LINK
 end
+
+functions -e add_path

src/build-remote/build-remote.cc

@@ -186,12 +186,12 @@ static int main_build_remote(int argc, char * * argv)
                         // build the hint template.
                         std::string errorText =
                             "Failed to find a machine for remote build!\n"
-                            "derivation: %s\nrequired (system, features): (%s, %s)";
+                            "derivation: %s\nrequired (system, features): (%s, [%s])";
                         errorText += "\n%s available machines:";
                         errorText += "\n(systems, maxjobs, supportedFeatures, mandatoryFeatures)";
 
                         for (unsigned int i = 0; i < machines.size(); ++i)
-                            errorText += "\n(%s, %s, %s, %s)";
+                            errorText += "\n([%s], %s, [%s], [%s])";
 
                         // add the template values.
                         std::string drvstr;

src/libcmd/command.cc

@@ -88,7 +88,8 @@ EvalCommand::EvalCommand()
 {
     addFlag({
         .longName = "debugger",
-        .description = "start an interactive environment if evaluation fails",
+        .description = "Start an interactive environment if evaluation fails.",
+        .category = MixEvalArgs::category,
         .handler = {&startReplOnEvalErrors, true},
     });
 }
@@ -225,7 +226,7 @@ MixProfile::MixProfile()
 {
     addFlag({
         .longName = "profile",
-        .description = "The profile to update.",
+        .description = "The profile to operate on.",
         .labels = {"path"},
         .handler = {&profile},
         .completer = completePath

src/libcmd/common-eval-args.cc

@@ -13,8 +13,6 @@ namespace nix {
 
 MixEvalArgs::MixEvalArgs()
 {
-    auto category = "Common evaluation options";
-
     addFlag({
         .longName = "arg",
         .description = "Pass the value *expr* as the argument *name* to Nix functions.",
@@ -34,7 +32,77 @@ MixEvalArgs::MixEvalArgs()
     addFlag({
         .longName = "include",
         .shortName = 'I',
-        .description = "Add *path* to the list of locations used to look up `<...>` file names.",
+        .description = R"(
+  Add *path* to the Nix search path. The Nix search path is
+  initialized from the colon-separated [`NIX_PATH`](@docroot@/command-ref/env-common.md#env-NIX_PATH) environment
+  variable, and is used to look up the location of Nix expressions using [paths](@docroot@/language/values.md#type-path) enclosed in angle
+  brackets (i.e., `<nixpkgs>`).
+
+  For instance, passing
+
+  ```
+  -I /home/eelco/Dev
+  -I /etc/nixos
+  ```
+
+  will cause Nix to look for paths relative to `/home/eelco/Dev` and
+  `/etc/nixos`, in that order. This is equivalent to setting the
+  `NIX_PATH` environment variable to
+
+  ```
+  /home/eelco/Dev:/etc/nixos
+  ```
+
+  It is also possible to match paths against a prefix. For example,
+  passing
+
+  ```
+  -I nixpkgs=/home/eelco/Dev/nixpkgs-branch
+  -I /etc/nixos
+  ```
+
+  will cause Nix to search for `<nixpkgs/path>` in
+  `/home/eelco/Dev/nixpkgs-branch/path` and `/etc/nixos/nixpkgs/path`.
+
+  If a path in the Nix search path starts with `http://` or `https://`,
+  it is interpreted as the URL of a tarball that will be downloaded and
+  unpacked to a temporary location. The tarball must consist of a single
+  top-level directory. For example, passing
+
+  ```
+  -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/master.tar.gz
+  ```
+
+  tells Nix to download and use the current contents of the `master`
+  branch in the `nixpkgs` repository.
+
+  The URLs of the tarballs from the official `nixos.org` channels
+  (see [the manual page for `nix-channel`](../nix-channel.md)) can be
+  abbreviated as `channel:<channel-name>`.  For instance, the
+  following two flags are equivalent:
+
+  ```
+  -I nixpkgs=channel:nixos-21.05
+  -I nixpkgs=https://nixos.org/channels/nixos-21.05/nixexprs.tar.xz
+  ```
+
+  You can also fetch source trees using [flake URLs](./nix3-flake.md#url-like-syntax) and add them to the
+  search path. For instance,
+
+  ```
+  -I nixpkgs=flake:nixpkgs
+  ```
+
+  specifies that the prefix `nixpkgs` shall refer to the source tree
+  downloaded from the `nixpkgs` entry in the flake registry. Similarly,
+
+  ```
+  -I nixpkgs=flake:github:NixOS/nixpkgs/nixos-22.05
+  ```
+
+  makes `<nixpkgs>` refer to a particular branch of the
+  `NixOS/nixpkgs` repository on GitHub.
+  )",
         .category = category,
         .labels = {"path"},
         .handler = {[&](std::string s) { searchPath.push_back(s); }}
@@ -91,14 +159,25 @@ Bindings * MixEvalArgs::getAutoArgs(EvalState & state)
 
 Path lookupFileArg(EvalState & state, std::string_view s)
 {
-    if (isUri(s)) {
-        return state.store->toRealPath(
-            fetchers::downloadTarball(
-                state.store, resolveUri(s), "source", false).first.storePath);
-    } else if (s.size() > 2 && s.at(0) == '<' && s.at(s.size() - 1) == '>') {
+    if (EvalSettings::isPseudoUrl(s)) {
+        auto storePath = fetchers::downloadTarball(
+            state.store, EvalSettings::resolvePseudoUrl(s), "source", false).first.storePath;
+        return state.store->toRealPath(storePath);
+    }
+
+    else if (hasPrefix(s, "flake:")) {
+        settings.requireExperimentalFeature(Xp::Flakes);
+        auto flakeRef = parseFlakeRef(std::string(s.substr(6)), {}, true, false);
+        auto storePath = flakeRef.resolve(state.store).fetchTree(state.store).first.storePath;
+        return state.store->toRealPath(storePath);
+    }
+
+    else if (s.size() > 2 && s.at(0) == '<' && s.at(s.size() - 1) == '>') {
         Path p(s.substr(1, s.size() - 2));
         return state.findFile(p);
-    } else
+    }
+
+    else
         return absPath(std::string(s));
 }
 

src/libcmd/common-eval-args.hh

@@ -10,6 +10,8 @@ class Bindings;
 
 struct MixEvalArgs : virtual Args
 {
+    static constexpr auto category = "Common evaluation options";
+
     MixEvalArgs();
 
     Bindings * getAutoArgs(EvalState & state);

src/libcmd/installables.cc

@@ -1,5 +1,6 @@
 #include "globals.hh"
 #include "installables.hh"
+#include "outputs-spec.hh"
 #include "util.hh"
 #include "command.hh"
 #include "attr-path.hh"
@@ -168,7 +169,7 @@ SourceExprCommand::SourceExprCommand(bool supportReadOnlyMode)
 
     addFlag({
         .longName = "derivation",
-        .description = "Operate on the store derivation rather than its outputs.",
+        .description = "Operate on the [store derivation](../../glossary.md#gloss-store-derivation) rather than its outputs.",
         .category = installablesCategory,
         .handler = {&operateOn, OperateOn::Derivation},
     });
@@ -207,55 +208,59 @@ Strings SourceExprCommand::getDefaultFlakeAttrPathPrefixes()
 
 void SourceExprCommand::completeInstallable(std::string_view prefix)
 {
-    if (file) {
-        completionType = ctAttrs;
+    try {
+        if (file) {
+            completionType = ctAttrs;
 
-        evalSettings.pureEval = false;
-        auto state = getEvalState();
-        Expr *e = state->parseExprFromFile(
-            resolveExprPath(state->checkSourcePath(lookupFileArg(*state, *file)))
-        );
+            evalSettings.pureEval = false;
+            auto state = getEvalState();
+            Expr *e = state->parseExprFromFile(
+                resolveExprPath(state->checkSourcePath(lookupFileArg(*state, *file)))
+                );
 
-        Value root;
-        state->eval(e, root);
+            Value root;
+            state->eval(e, root);
 
-        auto autoArgs = getAutoArgs(*state);
+            auto autoArgs = getAutoArgs(*state);
 
-        std::string prefix_ = std::string(prefix);
-        auto sep = prefix_.rfind('.');
-        std::string searchWord;
-        if (sep != std::string::npos) {
-            searchWord = prefix_.substr(sep + 1, std::string::npos);
-            prefix_ = prefix_.substr(0, sep);
-        } else {
-            searchWord = prefix_;
-            prefix_ = "";
-        }
+            std::string prefix_ = std::string(prefix);
+            auto sep = prefix_.rfind('.');
+            std::string searchWord;
+            if (sep != std::string::npos) {
+                searchWord = prefix_.substr(sep + 1, std::string::npos);
+                prefix_ = prefix_.substr(0, sep);
+            } else {
+                searchWord = prefix_;
+                prefix_ = "";
+            }
 
-        auto [v, pos] = findAlongAttrPath(*state, prefix_, *autoArgs, root);
-        Value &v1(*v);
-        state->forceValue(v1, pos);
-        Value v2;
-        state->autoCallFunction(*autoArgs, v1, v2);
+            auto [v, pos] = findAlongAttrPath(*state, prefix_, *autoArgs, root);
+            Value &v1(*v);
+            state->forceValue(v1, pos);
+            Value v2;
+            state->autoCallFunction(*autoArgs, v1, v2);
 
-        if (v2.type() == nAttrs) {
-            for (auto & i : *v2.attrs) {
-                std::string name = state->symbols[i.name];
-                if (name.find(searchWord) == 0) {
-                    if (prefix_ == "")
-                        completions->add(name);
-                    else
-                        completions->add(prefix_ + "." + name);
+            if (v2.type() == nAttrs) {
+                for (auto & i : *v2.attrs) {
+                    std::string name = state->symbols[i.name];
+                    if (name.find(searchWord) == 0) {
+                        if (prefix_ == "")
+                            completions->add(name);
+                        else
+                            completions->add(prefix_ + "." + name);
+                    }
                 }
             }
+        } else {
+            completeFlakeRefWithFragment(
+                getEvalState(),
+                lockFlags,
+                getDefaultFlakeAttrPathPrefixes(),
+                getDefaultFlakeAttrPaths(),
+                prefix);
         }
-    } else {
-        completeFlakeRefWithFragment(
-            getEvalState(),
-            lockFlags,
-            getDefaultFlakeAttrPathPrefixes(),
-            getDefaultFlakeAttrPaths(),
-            prefix);
+    } catch (EvalError&) {
+        // Don't want eval errors to mess-up with the completion engine, so let's just swallow them
     }
 }
 
@@ -354,7 +359,7 @@ void completeFlakeRef(ref<Store> store, std::string_view prefix)
     }
 }
 
-DerivedPath Installable::toDerivedPath()
+DerivedPathWithInfo Installable::toDerivedPath()
 {
     auto buildables = toDerivedPaths();
     if (buildables.size() != 1)
@@ -395,93 +400,53 @@ static StorePath getDeriver(
 struct InstallableStorePath : Installable
 {
     ref<Store> store;
-    StorePath storePath;
+    DerivedPath req;
 
-    InstallableStorePath(ref<Store> store, StorePath && storePath)
-        : store(store), storePath(std::move(storePath)) { }
+    InstallableStorePath(ref<Store> store, DerivedPath && req)
+        : store(store), req(std::move(req))
+    { }
 
-    std::string what() const override { return store->printStorePath(storePath); }
-
-    DerivedPaths toDerivedPaths() override
+    std::string what() const override
     {
-        if (storePath.isDerivation()) {
-            auto drv = store->readDerivation(storePath);
-            return {
-                DerivedPath::Built {
-                    .drvPath = storePath,
-                    .outputs = drv.outputNames(),
-                }
-            };
-        } else {
-            return {
-                DerivedPath::Opaque {
-                    .path = storePath,
-                }
-            };
-        }
+        return req.to_string(*store);
     }
 
-    StorePathSet toDrvPaths(ref<Store> store) override
+    DerivedPathsWithInfo toDerivedPaths() override
     {
-        if (storePath.isDerivation()) {
-            return {storePath};
-        } else {
-            return {getDeriver(store, *this, storePath)};
-        }
+        return {{.path = req, .info = {} }};
     }
 
     std::optional<StorePath> getStorePath() override
     {
-        return storePath;
+        return std::visit(overloaded {
+            [&](const DerivedPath::Built & bfd) {
+                return bfd.drvPath;
+            },
+            [&](const DerivedPath::Opaque & bo) {
+                return bo.path;
+            },
+        }, req.raw());
     }
 };
 
-DerivedPaths InstallableValue::toDerivedPaths()
-{
-    DerivedPaths res;
-
-    std::map<StorePath, std::set<std::string>> drvsToOutputs;
-    RealisedPath::Set drvsToCopy;
-
-    // Group by derivation, helps with .all in particular
-    for (auto & drv : toDerivations()) {
-        for (auto & outputName : drv.outputsToInstall)
-            drvsToOutputs[drv.drvPath].insert(outputName);
-        drvsToCopy.insert(drv.drvPath);
-    }
-
-    for (auto & i : drvsToOutputs)
-        res.push_back(DerivedPath::Built { i.first, i.second });
-
-    return res;
-}
-
-StorePathSet InstallableValue::toDrvPaths(ref<Store> store)
-{
-    StorePathSet res;
-    for (auto & drv : toDerivations())
-        res.insert(drv.drvPath);
-    return res;
-}
-
 struct InstallableAttrPath : InstallableValue
 {
     SourceExprCommand & cmd;
     RootValue v;
     std::string attrPath;
-    OutputsSpec outputsSpec;
+    ExtendedOutputsSpec extendedOutputsSpec;
 
     InstallableAttrPath(
         ref<EvalState> state,
         SourceExprCommand & cmd,
         Value * v,
         const std::string & attrPath,
-        OutputsSpec outputsSpec)
+        ExtendedOutputsSpec extendedOutputsSpec)
         : InstallableValue(state)
         , cmd(cmd)
         , v(allocRootValue(v))
         , attrPath(attrPath)
-        , outputsSpec(std::move(outputsSpec))
+        , extendedOutputsSpec(std::move(extendedOutputsSpec))
     { }
 
     std::string what() const override { return attrPath; }
@@ -493,40 +458,54 @@ struct InstallableAttrPath : InstallableValue
         return {vRes, pos};
     }
 
-    virtual std::vector<InstallableValue::DerivationInfo> toDerivations() override;
-};
+    DerivedPathsWithInfo toDerivedPaths() override
+    {
+        auto v = toValue(*state).first;
 
-std::vector<InstallableValue::DerivationInfo> InstallableAttrPath::toDerivations()
-{
-    auto v = toValue(*state).first;
+        Bindings & autoArgs = *cmd.getAutoArgs(*state);
 
-    Bindings & autoArgs = *cmd.getAutoArgs(*state);
+        DrvInfos drvInfos;
+        getDerivations(*state, *v, "", autoArgs, drvInfos, false);
 
-    DrvInfos drvInfos;
-    getDerivations(*state, *v, "", autoArgs, drvInfos, false);
+        // Backward compatibility hack: group results by drvPath. This
+        // helps keep .all output together.
+        std::map<StorePath, OutputsSpec> byDrvPath;
 
-    std::vector<DerivationInfo> res;
-    for (auto & drvInfo : drvInfos) {
-        auto drvPath = drvInfo.queryDrvPath();
-        if (!drvPath)
-            throw Error("'%s' is not a derivation", what());
+        for (auto & drvInfo : drvInfos) {
+            auto drvPath = drvInfo.queryDrvPath();
+            if (!drvPath)
+                throw Error("'%s' is not a derivation", what());
 
-        std::set<std::string> outputsToInstall;
+            auto newOutputs = std::visit(overloaded {
+                [&](const ExtendedOutputsSpec::Default & d) -> OutputsSpec {
+                    std::set<std::string> outputsToInstall;
+                    for (auto & output : drvInfo.queryOutputs(false, true))
+                        outputsToInstall.insert(output.first);
+                    return OutputsSpec::Names { std::move(outputsToInstall) };
+                },
+                [&](const ExtendedOutputsSpec::Explicit & e) -> OutputsSpec {
+                    return e;
+                },
+            }, extendedOutputsSpec.raw());
 
-        if (auto outputNames = std::get_if<OutputNames>(&outputsSpec))
-            outputsToInstall = *outputNames;
-        else
-            for (auto & output : drvInfo.queryOutputs(false, std::get_if<DefaultOutputs>(&outputsSpec)))
-                outputsToInstall.insert(output.first);
+            auto [iter, didInsert] = byDrvPath.emplace(*drvPath, newOutputs);
 
-        res.push_back(DerivationInfo {
-            .drvPath = *drvPath,
-            .outputsToInstall = std::move(outputsToInstall)
-        });
+            if (!didInsert)
+                iter->second = iter->second.union_(newOutputs);
+        }
+
+        DerivedPathsWithInfo res;
+        for (auto & [drvPath, outputs] : byDrvPath)
+            res.push_back({
+                .path = DerivedPath::Built {
+                    .drvPath = drvPath,
+                    .outputs = outputs,
+                },
+            });
+
+        return res;
     }
-
-    return res;
-}
+};
 
 std::vector<std::string> InstallableFlake::getActualAttrPaths()
 {
@@ -599,7 +578,7 @@ InstallableFlake::InstallableFlake(
     ref<EvalState> state,
     FlakeRef && flakeRef,
     std::string_view fragment,
-    OutputsSpec outputsSpec,
+    ExtendedOutputsSpec extendedOutputsSpec,
     Strings attrPaths,
     Strings prefixes,
     const flake::LockFlags & lockFlags)
@@ -607,14 +586,14 @@ InstallableFlake::InstallableFlake(
       flakeRef(flakeRef),
       attrPaths(fragment == "" ? attrPaths : Strings{(std::string) fragment}),
       prefixes(fragment == "" ? Strings{} : prefixes),
-      outputsSpec(std::move(outputsSpec)),
+      extendedOutputsSpec(std::move(extendedOutputsSpec)),
       lockFlags(lockFlags)
 {
     if (cmd && cmd->getAutoArgs(*state)->size())
         throw UsageError("'--arg' and '--argstr' are incompatible with flakes");
 }
 
-std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableFlake::toDerivation()
+DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
 {
     Activity act(*logger, lvlTalkative, actUnknown, fmt("evaluating derivation '%s'", what()));
 
@@ -622,56 +601,84 @@ std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableF
 
     auto attrPath = attr->getAttrPathStr();
 
-    if (!attr->isDerivation())
-        throw Error("flake output attribute '%s' is not a derivation", attrPath);
+    if (!attr->isDerivation()) {
+
+        // FIXME: use eval cache?
+        auto v = attr->forceValue();
+
+        if (v.type() == nPath) {
+            PathSet context;
+            auto storePath = state->copyPathToStore(context, Path(v.path));
+            return {{
+                .path = DerivedPath::Opaque {
+                    .path = std::move(storePath),
+                }
+            }};
+        }
+
+        else if (v.type() == nString) {
+            PathSet context;
+            auto s = state->forceString(v, context, noPos);
+            auto storePath = state->store->maybeParseStorePath(s);
+            if (storePath && context.count(std::string(s))) {
+                return {{
+                    .path = DerivedPath::Opaque {
+                        .path = std::move(*storePath),
+                    }
+                }};
+            } else
+                throw Error("flake output attribute '%s' evaluates to the string '%s' which is not a store path", attrPath, s);
+        }
+
+        else
+            throw Error("flake output attribute '%s' is not a derivation or path", attrPath);
+    }
 
     auto drvPath = attr->forceDerivation();
 
-    std::set<std::string> outputsToInstall;
     std::optional<NixInt> priority;
 
-    if (auto aOutputSpecified = attr->maybeGetAttr(state->sOutputSpecified)) {
-        if (aOutputSpecified->getBool()) {
-            if (auto aOutputName = attr->maybeGetAttr("outputName"))
-                outputsToInstall = { aOutputName->getString() };
-        }
-    }
-
-    else if (auto aMeta = attr->maybeGetAttr(state->sMeta)) {
-        if (auto aOutputsToInstall = aMeta->maybeGetAttr("outputsToInstall"))
-            for (auto & s : aOutputsToInstall->getListOfStrings())
-                outputsToInstall.insert(s);
+    if (attr->maybeGetAttr(state->sOutputSpecified)) {
+    } else if (auto aMeta = attr->maybeGetAttr(state->sMeta)) {
         if (auto aPriority = aMeta->maybeGetAttr("priority"))
             priority = aPriority->getInt();
     }
 
-    if (outputsToInstall.empty() || std::get_if<AllOutputs>(&outputsSpec)) {
-        outputsToInstall.clear();
-        if (auto aOutputs = attr->maybeGetAttr(state->sOutputs))
-            for (auto & s : aOutputs->getListOfStrings())
-                outputsToInstall.insert(s);
-    }
+    return {{
+        .path = DerivedPath::Built {
+            .drvPath = std::move(drvPath),
+            .outputs = std::visit(overloaded {
+                [&](const ExtendedOutputsSpec::Default & d) -> OutputsSpec {
+                    std::set<std::string> outputsToInstall;
+                    if (auto aOutputSpecified = attr->maybeGetAttr(state->sOutputSpecified)) {
+                        if (aOutputSpecified->getBool()) {
+                            if (auto aOutputName = attr->maybeGetAttr("outputName"))
+                                outputsToInstall = { aOutputName->getString() };
+                        }
+                    } else if (auto aMeta = attr->maybeGetAttr(state->sMeta)) {
+                        if (auto aOutputsToInstall = aMeta->maybeGetAttr("outputsToInstall"))
+                            for (auto & s : aOutputsToInstall->getListOfStrings())
+                                outputsToInstall.insert(s);
+                    }
 
-    if (outputsToInstall.empty())
-        outputsToInstall.insert("out");
+                    if (outputsToInstall.empty())
+                        outputsToInstall.insert("out");
 
-    if (auto outputNames = std::get_if<OutputNames>(&outputsSpec))
-        outputsToInstall = *outputNames;
-
-    auto drvInfo = DerivationInfo {
-        .drvPath = std::move(drvPath),
-        .outputsToInstall = std::move(outputsToInstall),
-        .priority = priority,
-    };
-
-    return {attrPath, getLockedFlake()->flake.lockedRef, std::move(drvInfo)};
-}
-
-std::vector<InstallableValue::DerivationInfo> InstallableFlake::toDerivations()
-{
-    std::vector<DerivationInfo> res;
-    res.push_back(std::get<2>(toDerivation()));
-    return res;
+                    return OutputsSpec::Names { std::move(outputsToInstall) };
+                },
+                [&](const ExtendedOutputsSpec::Explicit & e) -> OutputsSpec {
+                    return e;
+                },
+            }, extendedOutputsSpec.raw()),
+        },
+        .info = {
+            .priority = priority,
+            .originalRef = flakeRef,
+            .resolvedRef = getLockedFlake()->flake.lockedRef,
+            .attrPath = attrPath,
+            .extendedOutputsSpec = extendedOutputsSpec,
+        }
+    }};
 }
 
 std::pair<Value *, PosIdx> InstallableFlake::toValue(EvalState & state)
@@ -777,7 +784,8 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
         if (file == "-") {
             auto e = state->parseStdin();
             state->eval(e, *vFile);
-        } else if (file)
+        }
+        else if (file)
             state->evalFile(lookupFileArg(*state, *file), *vFile);
         else {
             auto e = state->parseExprFromString(*expr, absPath("."));
@@ -785,12 +793,12 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
         }
 
         for (auto & s : ss) {
-            auto [prefix, outputsSpec] = parseOutputsSpec(s);
+            auto [prefix, extendedOutputsSpec] = ExtendedOutputsSpec::parse(s);
             result.push_back(
                 std::make_shared<InstallableAttrPath>(
                     state, *this, vFile,
-                    prefix == "." ? "" : prefix,
-                    outputsSpec));
+                    prefix == "." ? "" : std::string { prefix },
+                    extendedOutputsSpec));
         }
 
     } else {
@@ -798,9 +806,46 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
         for (auto & s : ss) {
             std::exception_ptr ex;
 
-            if (s.find('/') != std::string::npos) {
+            auto [prefix_, extendedOutputsSpec_] = ExtendedOutputsSpec::parse(s);
+            // To avoid clang's pedantry
+            auto prefix = std::move(prefix_);
+            auto extendedOutputsSpec = std::move(extendedOutputsSpec_);
+
+            auto found = prefix.find('/');
+            if (found != std::string::npos) {
                 try {
-                    result.push_back(std::make_shared<InstallableStorePath>(store, store->followLinksToStorePath(s)));
+                    auto derivedPath = std::visit(overloaded {
+                        // If the user did not use ^, we treat the output more liberally.
+                        [&](const ExtendedOutputsSpec::Default &) -> DerivedPath {
+                            // First, we accept a symlink chain or an actual store path.
+                            auto storePath = store->followLinksToStorePath(prefix);
+                            // Second, we see if the store path ends in `.drv` to decide what sort
+                            // of derived path they want.
+                            //
+                            // This handling predates the `^` syntax. The `^*` in
+                            // `/nix/store/hash-foo.drv^*` unambiguously means "do the
+                            // `DerivedPath::Built` case", so plain `/nix/store/hash-foo.drv` could
+                            // also unambiguously mean "do the DerivedPath::Opaque` case".
+                            //
+                            // Issue #7261 tracks reconsidering this `.drv` dispatching.
+                            return storePath.isDerivation()
+                                ? (DerivedPath) DerivedPath::Built {
+                                    .drvPath = std::move(storePath),
+                                    .outputs = OutputsSpec::All {},
+                                }
+                                : (DerivedPath) DerivedPath::Opaque {
+                                    .path = std::move(storePath),
+                                };
+                        },
+                        // If the user did use ^, we just do exactly what is written.
+                        [&](const ExtendedOutputsSpec::Explicit & outputSpec) -> DerivedPath {
+                            return DerivedPath::Built {
+                                .drvPath = store->parseStorePath(prefix),
+                                .outputs = outputSpec,
+                            };
+                        },
+                    }, extendedOutputsSpec.raw());
+                    result.push_back(std::make_shared<InstallableStorePath>(store, std::move(derivedPath)));
                     continue;
                 } catch (BadStorePath &) {
                 } catch (...) {
@@ -810,13 +855,13 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
             }
 
             try {
-                auto [flakeRef, fragment, outputsSpec] = parseFlakeRefWithFragmentAndOutputsSpec(s, absPath("."));
+                auto [flakeRef, fragment] = parseFlakeRefWithFragment(std::string { prefix }, absPath("."));
                 result.push_back(std::make_shared<InstallableFlake>(
                         this,
                         getEvalState(),
                         std::move(flakeRef),
                         fragment,
-                        outputsSpec,
+                        extendedOutputsSpec,
                         getDefaultFlakeAttrPaths(),
                         getDefaultFlakeAttrPathPrefixes(),
                         lockFlags));
@@ -840,20 +885,20 @@ std::shared_ptr<Installable> SourceExprCommand::parseInstallable(
     return installables.front();
 }
 
-BuiltPaths Installable::build(
+std::vector<BuiltPathWithResult> Installable::build(
     ref<Store> evalStore,
     ref<Store> store,
     Realise mode,
     const std::vector<std::shared_ptr<Installable>> & installables,
     BuildMode bMode)
 {
-    BuiltPaths res;
-    for (auto & [_, builtPath] : build2(evalStore, store, mode, installables, bMode))
-        res.push_back(builtPath);
+    std::vector<BuiltPathWithResult> res;
+    for (auto & [_, builtPathWithResult] : build2(evalStore, store, mode, installables, bMode))
+        res.push_back(builtPathWithResult);
     return res;
 }
 
-std::vector<std::pair<std::shared_ptr<Installable>, BuiltPath>> Installable::build2(
+std::vector<std::pair<std::shared_ptr<Installable>, BuiltPathWithResult>> Installable::build2(
     ref<Store> evalStore,
     ref<Store> store,
     Realise mode,
@@ -863,17 +908,23 @@ std::vector<std::pair<std::shared_ptr<Installable>, BuiltPath>> Installable::bui
     if (mode == Realise::Nothing)
         settings.readOnlyMode = true;
 
+    struct Aux
+    {
+        ExtraPathInfo info;
+        std::shared_ptr<Installable> installable;
+    };
+
     std::vector<DerivedPath> pathsToBuild;
-    std::map<DerivedPath, std::vector<std::shared_ptr<Installable>>> backmap;
+    std::map<DerivedPath, std::vector<Aux>> backmap;
 
     for (auto & i : installables) {
         for (auto b : i->toDerivedPaths()) {
-            pathsToBuild.push_back(b);
-            backmap[b].push_back(i);
+            pathsToBuild.push_back(b.path);
+            backmap[b.path].push_back({.info = b.info, .installable = i});
         }
     }
 
-    std::vector<std::pair<std::shared_ptr<Installable>, BuiltPath>> res;
+    std::vector<std::pair<std::shared_ptr<Installable>, BuiltPathWithResult>> res;
 
     switch (mode) {
 
@@ -882,42 +933,18 @@ std::vector<std::pair<std::shared_ptr<Installable>, BuiltPath>> Installable::bui
         printMissing(store, pathsToBuild, lvlError);
 
         for (auto & path : pathsToBuild) {
-            for (auto & installable : backmap[path]) {
+            for (auto & aux : backmap[path]) {
                 std::visit(overloaded {
                     [&](const DerivedPath::Built & bfd) {
-                        OutputPathMap outputs;
-                        auto drv = evalStore->readDerivation(bfd.drvPath);
-                        auto outputHashes = staticOutputHashes(*evalStore, drv); // FIXME: expensive
-                        auto drvOutputs = drv.outputsAndOptPaths(*store);
-                        for (auto & output : bfd.outputs) {
-                            auto outputHash = get(outputHashes, output);
-                            if (!outputHash)
-                                throw Error(
-                                    "the derivation '%s' doesn't have an output named '%s'",
-                                    store->printStorePath(bfd.drvPath), output);
-                            if (settings.isExperimentalFeatureEnabled(Xp::CaDerivations)) {
-                                DrvOutput outputId { *outputHash, output };
-                                auto realisation = store->queryRealisation(outputId);
-                                if (!realisation)
-                                    throw Error(
-                                        "cannot operate on an output of the "
-                                        "unbuilt derivation '%s'",
-                                        outputId.to_string());
-                                outputs.insert_or_assign(output, realisation->outPath);
-                            } else {
-                                // If ca-derivations isn't enabled, assume that
-                                // the output path is statically known.
-                                auto drvOutput = get(drvOutputs, output);
-                                assert(drvOutput);
-                                assert(drvOutput->second);
-                                outputs.insert_or_assign(
-                                    output, *drvOutput->second);
-                            }
-                        }
-                        res.push_back({installable, BuiltPath::Built { bfd.drvPath, outputs }});
+                        auto outputs = resolveDerivedPath(*store, bfd, &*evalStore);
+                        res.push_back({aux.installable, {
+                            .path = BuiltPath::Built { bfd.drvPath, outputs },
+                            .info = aux.info}});
                     },
                     [&](const DerivedPath::Opaque & bo) {
-                        res.push_back({installable, BuiltPath::Opaque { bo.path }});
+                        res.push_back({aux.installable, {
+                            .path = BuiltPath::Opaque { bo.path },
+                            .info = aux.info}});
                     },
                 }, path.raw());
             }
@@ -927,22 +954,28 @@ std::vector<std::pair<std::shared_ptr<Installable>, BuiltPath>> Installable::bui
 
     case Realise::Outputs: {
         if (settings.printMissing)
-          printMissing(store, pathsToBuild, lvlInfo);
+            printMissing(store, pathsToBuild, lvlInfo);
 
         for (auto & buildResult : store->buildPathsWithResults(pathsToBuild, bMode, evalStore)) {
             if (!buildResult.success())
                 buildResult.rethrow();
 
-            for (auto & installable : backmap[buildResult.path]) {
+            for (auto & aux : backmap[buildResult.path]) {
                 std::visit(overloaded {
                     [&](const DerivedPath::Built & bfd) {
                         std::map<std::string, StorePath> outputs;
                         for (auto & path : buildResult.builtOutputs)
                             outputs.emplace(path.first.outputName, path.second.outPath);
-                        res.push_back({installable, BuiltPath::Built { bfd.drvPath, outputs }});
+                        res.push_back({aux.installable, {
+                            .path = BuiltPath::Built { bfd.drvPath, outputs },
+                            .info = aux.info,
+                            .result = buildResult}});
                     },
                     [&](const DerivedPath::Opaque & bo) {
-                        res.push_back({installable, BuiltPath::Opaque { bo.path }});
+                        res.push_back({aux.installable, {
+                            .path = BuiltPath::Opaque { bo.path },
+                            .info = aux.info,
+                            .result = buildResult}});
                     },
                 }, buildResult.path.raw());
             }
@@ -965,9 +998,12 @@ BuiltPaths Installable::toBuiltPaths(
     OperateOn operateOn,
     const std::vector<std::shared_ptr<Installable>> & installables)
 {
-    if (operateOn == OperateOn::Output)
-        return Installable::build(evalStore, store, mode, installables);
-    else {
+    if (operateOn == OperateOn::Output) {
+        BuiltPaths res;
+        for (auto & p : Installable::build(evalStore, store, mode, installables))
+            res.push_back(p.path);
+        return res;
+    } else {
         if (mode == Realise::Nothing)
             settings.readOnlyMode = true;
 
@@ -1024,7 +1060,7 @@ StorePathSet Installable::toDerivations(
                 [&](const DerivedPath::Built & bfd) {
                     drvPaths.insert(bfd.drvPath);
                 },
-            }, b.raw());
+            }, b.path.raw());
 
     return drvPaths;
 }

src/libcmd/installables.hh

@@ -2,11 +2,12 @@
 
 #include "util.hh"
 #include "path.hh"
-#include "path-with-outputs.hh"
+#include "outputs-spec.hh"
 #include "derived-path.hh"
 #include "eval.hh"
 #include "store-api.hh"
 #include "flake/flake.hh"
+#include "build-result.hh"
 
 #include <optional>
 
@@ -19,7 +20,7 @@ namespace eval_cache { class EvalCache; class AttrCursor; }
 
 struct App
 {
-    std::vector<StorePathWithOutputs> context;
+    std::vector<DerivedPath> context;
     Path program;
     // FIXME: add args, sandbox settings, metadata, ...
 };
@@ -51,20 +52,42 @@ enum class OperateOn {
     Derivation
 };
 
+struct ExtraPathInfo
+{
+    std::optional<NixInt> priority;
+    std::optional<FlakeRef> originalRef;
+    std::optional<FlakeRef> resolvedRef;
+    std::optional<std::string> attrPath;
+    // FIXME: merge with DerivedPath's 'outputs' field?
+    std::optional<ExtendedOutputsSpec> extendedOutputsSpec;
+};
+
+/* A derived path with any additional info that commands might
+   need from the derivation. */
+struct DerivedPathWithInfo
+{
+    DerivedPath path;
+    ExtraPathInfo info;
+};
+
+struct BuiltPathWithResult
+{
+    BuiltPath path;
+    ExtraPathInfo info;
+    std::optional<BuildResult> result;
+};
+
+typedef std::vector<DerivedPathWithInfo> DerivedPathsWithInfo;
+
 struct Installable
 {
     virtual ~Installable() { }
 
     virtual std::string what() const = 0;
 
-    virtual DerivedPaths toDerivedPaths() = 0;
+    virtual DerivedPathsWithInfo toDerivedPaths() = 0;
 
-    virtual StorePathSet toDrvPaths(ref<Store> store)
-    {
-        throw Error("'%s' cannot be converted to a derivation path", what());
-    }
-
-    DerivedPath toDerivedPath();
+    DerivedPathWithInfo toDerivedPath();
 
     UnresolvedApp toApp(EvalState & state);
 
@@ -91,14 +114,14 @@ struct Installable
         return FlakeRef::fromAttrs({{"type","indirect"}, {"id", "nixpkgs"}});
     }
 
-    static BuiltPaths build(
+    static std::vector<BuiltPathWithResult> build(
         ref<Store> evalStore,
         ref<Store> store,
         Realise mode,
         const std::vector<std::shared_ptr<Installable>> & installables,
         BuildMode bMode = bmNormal);
 
-    static std::vector<std::pair<std::shared_ptr<Installable>, BuiltPath>> build2(
+    static std::vector<std::pair<std::shared_ptr<Installable>, BuiltPathWithResult>> build2(
         ref<Store> evalStore,
         ref<Store> store,
         Realise mode,
@@ -139,19 +162,6 @@ struct InstallableValue : Installable
     ref<EvalState> state;
 
     InstallableValue(ref<EvalState> state) : state(state) {}
-
-    struct DerivationInfo
-    {
-        StorePath drvPath;
-        std::set<std::string> outputsToInstall;
-        std::optional<NixInt> priority;
-    };
-
-    virtual std::vector<DerivationInfo> toDerivations() = 0;
-
-    DerivedPaths toDerivedPaths() override;
-
-    StorePathSet toDrvPaths(ref<Store> store) override;
 };
 
 struct InstallableFlake : InstallableValue
@@ -159,7 +169,7 @@ struct InstallableFlake : InstallableValue
     FlakeRef flakeRef;
     Strings attrPaths;
     Strings prefixes;
-    OutputsSpec outputsSpec;
+    ExtendedOutputsSpec extendedOutputsSpec;
     const flake::LockFlags & lockFlags;
     mutable std::shared_ptr<flake::LockedFlake> _lockedFlake;
 
@@ -168,7 +178,7 @@ struct InstallableFlake : InstallableValue
         ref<EvalState> state,
         FlakeRef && flakeRef,
         std::string_view fragment,
-        OutputsSpec outputsSpec,
+        ExtendedOutputsSpec extendedOutputsSpec,
         Strings attrPaths,
         Strings prefixes,
         const flake::LockFlags & lockFlags);
@@ -179,9 +189,7 @@ struct InstallableFlake : InstallableValue
 
     Value * getFlakeOutputs(EvalState & state, const flake::LockedFlake & lockedFlake);
 
-    std::tuple<std::string, FlakeRef, DerivationInfo> toDerivation();
-
-    std::vector<DerivationInfo> toDerivations() override;
+    DerivedPathsWithInfo toDerivedPaths() override;
 
     std::pair<Value *, PosIdx> toValue(EvalState & state) override;
 

src/libcmd/local.mk

@@ -8,7 +8,7 @@ libcmd_SOURCES := $(wildcard $(d)/*.cc)
 
 libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain -I src/libfetchers -I src/nix
 
-libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown -pthread
+libcmd_LDFLAGS = $(EDITLINE_LIBS) $(LOWDOWN_LIBS) -pthread
 
 libcmd_LIBS = libstore libutil libexpr libmain libfetchers
 

src/libcmd/repl.cc

@@ -215,17 +215,15 @@ static std::ostream & showDebugTrace(std::ostream & out, const PosTable & positi
     out << dt.hint.str() << "\n";
 
     // prefer direct pos, but if noPos then try the expr.
-    auto pos = *dt.pos
-        ? *dt.pos
-        : positions[dt.expr.getPos() ? dt.expr.getPos() : noPos];
+    auto pos = dt.pos
+        ? dt.pos
+        : static_cast<std::shared_ptr<AbstractPos>>(positions[dt.expr.getPos() ? dt.expr.getPos() : noPos]);
 
     if (pos) {
-        printAtPos(pos, out);
-
-        auto loc = getCodeLines(pos);
-        if (loc.has_value()) {
+        out << pos;
+        if (auto loc = pos->getCodeLines()) {
             out << "\n";
-            printCodeLines(out, "", pos, *loc);
+            printCodeLines(out, "", *pos, *loc);
             out << "\n";
         }
     }
@@ -270,6 +268,7 @@ void NixRepl::mainLoop()
             // ctrl-D should exit the debugger.
             state->debugStop = false;
             state->debugQuit = true;
+            logger->cout("");
             break;
         }
         try {
@@ -384,6 +383,10 @@ StringSet NixRepl::completePrefix(const std::string & prefix)
             i++;
         }
     } else {
+        /* Temporarily disable the debugger, to avoid re-entering readline. */
+        auto debug_repl = state->debugRepl;
+        state->debugRepl = nullptr;
+        Finally restoreDebug([&]() { state->debugRepl = debug_repl; });
         try {
             /* This is an expression that should evaluate to an
                attribute set.  Evaluate it to get the names of the
@@ -584,15 +587,17 @@ bool NixRepl::processLine(std::string line)
         Value v;
         evalString(arg, v);
 
-        const auto [file, line] = [&] () -> std::pair<std::string, uint32_t> {
+        const auto [path, line] = [&] () -> std::pair<Path, uint32_t> {
             if (v.type() == nPath || v.type() == nString) {
                 PathSet context;
-                auto filename = state->coerceToString(noPos, v, context).toOwned();
-                state->symbols.create(filename);
-                return {filename, 0};
+                auto path = state->coerceToPath(noPos, v, context);
+                return {path, 0};
             } else if (v.isLambda()) {
                 auto pos = state->positions[v.lambda.fun->pos];
-                return {pos.file, pos.line};
+                if (auto path = std::get_if<Path>(&pos.origin))
+                    return {*path, pos.line};
+                else
+                    throw Error("'%s' cannot be shown in an editor", pos);
             } else {
                 // assume it's a derivation
                 return findPackageFilename(*state, v, arg);
@@ -600,7 +605,7 @@ bool NixRepl::processLine(std::string line)
         }();
 
         // Open in EDITOR
-        auto args = editorFor(file, line);
+        auto args = editorFor(path, line);
         auto editor = args.front();
         args.pop_front();
 
@@ -636,7 +641,12 @@ bool NixRepl::processLine(std::string line)
         Path drvPathRaw = state->store->printStorePath(drvPath);
 
         if (command == ":b" || command == ":bl") {
-            state->store->buildPaths({DerivedPath::Built{drvPath}});
+            state->store->buildPaths({
+                DerivedPath::Built {
+                    .drvPath = drvPath,
+                    .outputs = OutputsSpec::All { },
+                },
+            });
             auto drv = state->store->readDerivation(drvPath);
             logger->cout("\nThis derivation produced the following outputs:");
             for (auto & [outputName, outputPath] : state->store->queryDerivationOutputMap(drvPath)) {
@@ -782,7 +792,7 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
             flake::LockFlags {
                 .updateLockFile = false,
                 .useRegistries = !evalSettings.pureEval,
-                .allowMutable  = !evalSettings.pureEval,
+                .allowUnlocked = !evalSettings.pureEval,
             }),
         v);
     addAttrsToScope(v);
@@ -1050,7 +1060,7 @@ struct CmdRepl : InstallablesCommand
         evalSettings.pureEval = false;
     }
 
-    void prepare()
+    void prepare() override
     {
         if (!settings.isExperimentalFeatureEnabled(Xp::ReplFlake) && !(file) && this->_installables.size() >= 1) {
             warn("future versions of Nix will require using `--file` to load a file");

src/libexpr/eval-cache.cc

@@ -300,7 +300,7 @@ struct AttrDb
                 NixStringContext context;
                 if (!queryAttribute.isNull(3))
                     for (auto & s : tokenizeString<std::vector<std::string>>(queryAttribute.getStr(3), ";"))
-                        context.push_back(decodeContext(cfg, s));
+                        context.push_back(NixStringContextElem::parse(cfg, s));
                 return {{rowId, string_t{queryAttribute.getStr(2), context}}};
             }
             case AttrType::Bool:
@@ -592,7 +592,18 @@ string_t AttrCursor::getStringWithContext()
             if (auto s = std::get_if<string_t>(&cachedValue->second)) {
                 bool valid = true;
                 for (auto & c : s->second) {
-                    if (!root->state.store->isValidPath(c.first)) {
+                    const StorePath & path = std::visit(overloaded {
+                        [&](const NixStringContextElem::DrvDeep & d) -> const StorePath & {
+                            return d.drvPath;
+                        },
+                        [&](const NixStringContextElem::Built & b) -> const StorePath & {
+                            return b.drvPath;
+                        },
+                        [&](const NixStringContextElem::Opaque & o) -> const StorePath & {
+                            return o.path;
+                        },
+                    }, c.raw());
+                    if (!root->state.store->isValidPath(path)) {
                         valid = false;
                         break;
                     }
@@ -645,17 +656,17 @@ NixInt AttrCursor::getInt()
             cachedValue = root->db->getAttr(getKey());
         if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
             if (auto i = std::get_if<int_t>(&cachedValue->second)) {
-                debug("using cached Integer attribute '%s'", getAttrPathStr());
+                debug("using cached integer attribute '%s'", getAttrPathStr());
                 return i->x;
             } else
-                throw TypeError("'%s' is not an Integer", getAttrPathStr());
+                throw TypeError("'%s' is not an integer", getAttrPathStr());
         }
     }
 
     auto & v = forceValue();
 
     if (v.type() != nInt)
-        throw TypeError("'%s' is not an Integer", getAttrPathStr());
+        throw TypeError("'%s' is not an integer", getAttrPathStr());
 
     return v.integer;
 }

src/libexpr/eval.cc

@@ -7,7 +7,6 @@
 #include "globals.hh"
 #include "eval-inline.hh"
 #include "filetransfer.hh"
-#include "json.hh"
 #include "function-trace.hh"
 
 #include <algorithm>
@@ -21,6 +20,7 @@
 #include <functional>
 
 #include <sys/resource.h>
+#include <nlohmann/json.hpp>
 
 #if HAVE_BOEHMGC
 
@@ -35,6 +35,8 @@
 
 #endif
 
+using json = nlohmann::json;
+
 namespace nix {
 
 static char * allocString(size_t size)
@@ -43,7 +45,7 @@ static char * allocString(size_t size)
 #if HAVE_BOEHMGC
     t = (char *) GC_MALLOC_ATOMIC(size);
 #else
-    t = malloc(size);
+    t = (char *) malloc(size);
 #endif
     if (!t) throw std::bad_alloc();
     return t;
@@ -65,26 +67,19 @@ static char * dupString(const char * s)
 
 // When there's no need to write to the string, we can optimize away empty
 // string allocations.
-// This function handles makeImmutableStringWithLen(null, 0) by returning the
-// empty string.
-static const char * makeImmutableStringWithLen(const char * s, size_t size)
+// This function handles makeImmutableString(std::string_view()) by returning
+// the empty string.
+static const char * makeImmutableString(std::string_view s)
 {
-    char * t;
+    const size_t size = s.size();
     if (size == 0)
         return "";
-#if HAVE_BOEHMGC
-    t = GC_STRNDUP(s, size);
-#else
-    t = strndup(s, size);
-#endif
-    if (!t) throw std::bad_alloc();
+    auto t = allocString(size + 1);
+    memcpy(t, s.data(), size);
+    t[size] = '\0';
     return t;
 }
 
-static inline const char * makeImmutableString(std::string_view s) {
-    return makeImmutableStringWithLen(s.data(), s.size());
-}
-
 
 RootValue allocRootValue(Value * v)
 {
@@ -404,7 +399,8 @@ static Strings parseNixPath(const std::string & s)
         }
 
         if (*p == ':') {
-            if (isUri(std::string(start2, s.end()))) {
+            auto prefix = std::string(start2, s.end());
+            if (EvalSettings::isPseudoUrl(prefix) || hasPrefix(prefix, "flake:")) {
                 ++p;
                 while (p != s.end() && *p != ':') ++p;
             }
@@ -472,9 +468,6 @@ EvalState::EvalState(
 #if HAVE_BOEHMGC
     , valueAllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
     , env1AllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
-#else
-    , valueAllocCache(std::make_shared<void *>(nullptr))
-    , env1AllocCache(std::make_shared<void *>(nullptr))
 #endif
     , baseEnv(allocEnv(128))
     , staticBaseEnv{std::make_shared<StaticEnv>(false, nullptr)}
@@ -824,7 +817,7 @@ void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr &
         ? std::make_unique<DebugTraceStacker>(
             *this,
             DebugTrace {
-                .pos = error->info().errPos ? *error->info().errPos : positions[expr.getPos()],
+                .pos = error->info().errPos ? error->info().errPos : static_cast<std::shared_ptr<AbstractPos>>(positions[expr.getPos()]),
                 .expr = expr,
                 .env = env,
                 .hint = error->info().msg,
@@ -904,7 +897,7 @@ void EvalState::throwEvalError(const char * s, const std::string & s2,
     const std::string & s3)
 {
     debugThrowLastTrace(EvalError({
-        .msg = hintfmt(s, s2),
+        .msg = hintfmt(s, s2, s3),
         .errPos = positions[noPos]
     }));
 }
@@ -913,7 +906,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
     const std::string & s3)
 {
     debugThrowLastTrace(EvalError({
-        .msg = hintfmt(s, s2),
+        .msg = hintfmt(s, s2, s3),
         .errPos = positions[pos]
     }));
 }
@@ -922,7 +915,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
     const std::string & s3, Env & env, Expr & expr)
 {
     debugThrow(EvalError({
-        .msg = hintfmt(s, s2),
+        .msg = hintfmt(s, s2, s3),
         .errPos = positions[pos]
     }), env, expr);
 }
@@ -1013,7 +1006,7 @@ void EvalState::throwMissingArgumentError(const PosIdx pos, const char * s, cons
 
 void EvalState::addErrorTrace(Error & e, const char * s, const std::string & s2) const
 {
-    e.addTrace(std::nullopt, s, s2);
+    e.addTrace(nullptr, s, s2);
 }
 
 void EvalState::addErrorTrace(Error & e, const PosIdx pos, const char * s, const std::string & s2) const
@@ -1025,13 +1018,13 @@ static std::unique_ptr<DebugTraceStacker> makeDebugTraceStacker(
     EvalState & state,
     Expr & expr,
     Env & env,
-    std::optional<ErrPos> pos,
+    std::shared_ptr<AbstractPos> && pos,
     const char * s,
     const std::string & s2)
 {
     return std::make_unique<DebugTraceStacker>(state,
         DebugTrace {
-            .pos = pos,
+            .pos = std::move(pos),
             .expr = expr,
             .env = env,
             .hint = hintfmt(s, s2),
@@ -1137,9 +1130,9 @@ void EvalState::mkThunk_(Value & v, Expr * expr)
 void EvalState::mkPos(Value & v, PosIdx p)
 {
     auto pos = positions[p];
-    if (!pos.file.empty()) {
+    if (auto path = std::get_if<Path>(&pos.origin)) {
         auto attrs = buildBindings(3);
-        attrs.alloc(sFile).mkString(pos.file);
+        attrs.alloc(sFile).mkString(*path);
         attrs.alloc(sLine).mkInt(pos.line);
         attrs.alloc(sColumn).mkInt(pos.column);
         v.mkAttrs(attrs);
@@ -1247,7 +1240,7 @@ void EvalState::cacheFile(
                 *this,
                 *e,
                 this->baseEnv,
-                e->getPos() ? std::optional(ErrPos(positions[e->getPos()])) : std::nullopt,
+                e->getPos() ? static_cast<std::shared_ptr<AbstractPos>>(positions[e->getPos()]) : nullptr,
                 "while evaluating the file '%1%':", resolvedPath)
             : nullptr;
 
@@ -1518,10 +1511,13 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
         state.forceValue(*vAttrs, (pos2 ? pos2 : this->pos ) );
 
     } catch (Error & e) {
-        auto pos2r = state.positions[pos2];
-        if (pos2 && pos2r.file != state.derivationNixPath)
-            state.addErrorTrace(e, pos2, "while evaluating the attribute '%1%'",
-                showAttrPath(state, env, attrPath));
+        if (pos2) {
+            auto pos2r = state.positions[pos2];
+            auto origin = std::get_if<Path>(&pos2r.origin);
+            if (!(origin && *origin == state.derivationNixPath))
+                state.addErrorTrace(e, pos2, "while evaluating the attribute '%1%'",
+                    showAttrPath(state, env, attrPath));
+        }
         throw;
     }
 
@@ -1648,7 +1644,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
                 auto dts = debugRepl
                     ? makeDebugTraceStacker(
                         *this, *lambda.body, env2, positions[lambda.pos],
-                        "while evaluating %s",
+                        "while calling %s",
                         lambda.name
                         ? concatStrings("'", symbols[lambda.name], "'")
                         : "anonymous lambda")
@@ -1657,11 +1653,11 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
                 lambda.body->eval(*this, env2, vCur);
             } catch (Error & e) {
                 if (loggerSettings.showTrace.get()) {
-                    addErrorTrace(e, lambda.pos, "while evaluating %s",
+                    addErrorTrace(e, lambda.pos, "while calling %s",
                         (lambda.name
                             ? concatStrings("'", symbols[lambda.name], "'")
                             : "anonymous lambda"));
-                    addErrorTrace(e, pos, "from call site%s", "");
+                    addErrorTrace(e, pos, "while evaluating call site%s", "");
                 }
                 throw;
             }
@@ -1808,7 +1804,7 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
 Nix attempted to evaluate a function as a top level expression; in
 this case it must have its arguments supplied either by default
 values, or passed explicitly with '--arg' or '--argstr'. See
-https://nixos.org/manual/nix/stable/expressions/language-constructs.html#functions.)", symbols[i.name],                 
+https://nixos.org/manual/nix/stable/language/constructs.html#functions.)", symbols[i.name],
                 *fun.lambda.env, *fun.lambda.fun);
             }
         }
@@ -2149,27 +2145,6 @@ std::string_view EvalState::forceString(Value & v, const PosIdx pos)
 }
 
 
-/* Decode a context string ‘!<name>!<path>’ into a pair <path,
-   name>. */
-NixStringContextElem decodeContext(const Store & store, std::string_view s)
-{
-    if (s.at(0) == '!') {
-        size_t index = s.find("!", 1);
-        return {
-            store.parseStorePath(s.substr(index + 1)),
-            std::string(s.substr(1, index - 1)),
-        };
-    } else
-        return {
-            store.parseStorePath(
-                s.at(0) == '/'
-                ? s
-                : s.substr(1)),
-            "",
-        };
-}
-
-
 void copyContext(const Value & v, PathSet & context)
 {
     if (v.string.context)
@@ -2184,7 +2159,7 @@ NixStringContext Value::getContext(const Store & store)
     assert(internalType == tString);
     if (string.context)
         for (const char * * p = string.context; *p; ++p)
-            res.push_back(decodeContext(store, *p));
+            res.push_back(NixStringContextElem::parse(store, *p));
     return res;
 }
 
@@ -2251,7 +2226,7 @@ BackedStringView EvalState::coerceToString(const PosIdx pos, Value & v, PathSet
         if (canonicalizePath)
             path = canonPath(*path);
         if (copyToStore)
-            path = copyPathToStore(context, std::move(path).toOwned());
+            path = store->printStorePath(copyPathToStore(context, std::move(path).toOwned()));
         return path;
     }
 
@@ -2294,26 +2269,26 @@ BackedStringView EvalState::coerceToString(const PosIdx pos, Value & v, PathSet
 }
 
 
-std::string EvalState::copyPathToStore(PathSet & context, const Path & path)
+StorePath EvalState::copyPathToStore(PathSet & context, const Path & path)
 {
     if (nix::isDerivation(path))
         throwEvalError("file names are not allowed to end in '%1%'", drvExtension);
 
-    Path dstPath;
-    auto i = srcToStore.find(path);
-    if (i != srcToStore.end())
-        dstPath = store->printStorePath(i->second);
-    else {
-        auto p = settings.readOnlyMode
+    auto dstPath = [&]() -> StorePath
+    {
+        auto i = srcToStore.find(path);
+        if (i != srcToStore.end()) return i->second;
+
+        auto dstPath = settings.readOnlyMode
             ? store->computeStorePathForPath(std::string(baseNameOf(path)), checkSourcePath(path)).first
             : store->addToStore(std::string(baseNameOf(path)), checkSourcePath(path), FileIngestionMethod::Recursive, htSHA256, defaultPathFilter, repair);
-        dstPath = store->printStorePath(p);
-        allowPath(p);
-        srcToStore.insert_or_assign(path, std::move(p));
-        printMsg(lvlChatty, "copied source '%1%' -> '%2%'", path, dstPath);
-    }
+        allowPath(dstPath);
+        srcToStore.insert_or_assign(path, dstPath);
+        printMsg(lvlChatty, "copied source '%1%' -> '%2%'", path, store->printStorePath(dstPath));
+        return dstPath;
+    }();
 
-    context.insert(dstPath);
+    context.insert(store->printStorePath(dstPath));
     return dstPath;
 }
 
@@ -2441,97 +2416,99 @@ void EvalState::printStats()
         std::fstream fs;
         if (outPath != "-")
             fs.open(outPath, std::fstream::out);
-        JSONObject topObj(outPath == "-" ? std::cerr : fs, true);
-        topObj.attr("cpuTime",cpuTime);
-        {
-            auto envs = topObj.object("envs");
-            envs.attr("number", nrEnvs);
-            envs.attr("elements", nrValuesInEnvs);
-            envs.attr("bytes", bEnvs);
-        }
-        {
-            auto lists = topObj.object("list");
-            lists.attr("elements", nrListElems);
-            lists.attr("bytes", bLists);
-            lists.attr("concats", nrListConcats);
-        }
-        {
-            auto values = topObj.object("values");
-            values.attr("number", nrValues);
-            values.attr("bytes", bValues);
-        }
-        {
-            auto syms = topObj.object("symbols");
-            syms.attr("number", symbols.size());
-            syms.attr("bytes", symbols.totalSize());
-        }
-        {
-            auto sets = topObj.object("sets");
-            sets.attr("number", nrAttrsets);
-            sets.attr("bytes", bAttrsets);
-            sets.attr("elements", nrAttrsInAttrsets);
-        }
-        {
-            auto sizes = topObj.object("sizes");
-            sizes.attr("Env", sizeof(Env));
-            sizes.attr("Value", sizeof(Value));
-            sizes.attr("Bindings", sizeof(Bindings));
-            sizes.attr("Attr", sizeof(Attr));
-        }
-        topObj.attr("nrOpUpdates", nrOpUpdates);
-        topObj.attr("nrOpUpdateValuesCopied", nrOpUpdateValuesCopied);
-        topObj.attr("nrThunks", nrThunks);
-        topObj.attr("nrAvoided", nrAvoided);
-        topObj.attr("nrLookups", nrLookups);
-        topObj.attr("nrPrimOpCalls", nrPrimOpCalls);
-        topObj.attr("nrFunctionCalls", nrFunctionCalls);
+        json topObj = json::object();
+        topObj["cpuTime"] = cpuTime;
+        topObj["envs"] = {
+            {"number", nrEnvs},
+            {"elements", nrValuesInEnvs},
+            {"bytes", bEnvs},
+        };
+        topObj["list"] = {
+            {"elements", nrListElems},
+            {"bytes", bLists},
+            {"concats", nrListConcats},
+        };
+        topObj["values"] = {
+            {"number", nrValues},
+            {"bytes", bValues},
+        };
+        topObj["symbols"] = {
+            {"number", symbols.size()},
+            {"bytes", symbols.totalSize()},
+        };
+        topObj["sets"] = {
+            {"number", nrAttrsets},
+            {"bytes", bAttrsets},
+            {"elements", nrAttrsInAttrsets},
+        };
+        topObj["sizes"] = {
+            {"Env", sizeof(Env)},
+            {"Value", sizeof(Value)},
+            {"Bindings", sizeof(Bindings)},
+            {"Attr", sizeof(Attr)},
+        };
+        topObj["nrOpUpdates"] = nrOpUpdates;
+        topObj["nrOpUpdateValuesCopied"] = nrOpUpdateValuesCopied;
+        topObj["nrThunks"] = nrThunks;
+        topObj["nrAvoided"] = nrAvoided;
+        topObj["nrLookups"] = nrLookups;
+        topObj["nrPrimOpCalls"] = nrPrimOpCalls;
+        topObj["nrFunctionCalls"] = nrFunctionCalls;
 #if HAVE_BOEHMGC
-        {
-            auto gc = topObj.object("gc");
-            gc.attr("heapSize", heapSize);
-            gc.attr("totalBytes", totalBytes);
-        }
+        topObj["gc"] = {
+            {"heapSize", heapSize},
+            {"totalBytes", totalBytes},
+        };
 #endif
 
         if (countCalls) {
+            topObj["primops"] = primOpCalls;
             {
-                auto obj = topObj.object("primops");
-                for (auto & i : primOpCalls)
-                    obj.attr(i.first, i.second);
-            }
-            {
-                auto list = topObj.list("functions");
+                auto& list = topObj["functions"];
+                list = json::array();
                 for (auto & [fun, count] : functionCalls) {
-                    auto obj = list.object();
+                    json obj = json::object();
                     if (fun->name)
-                        obj.attr("name", (std::string_view) symbols[fun->name]);
+                        obj["name"] = (std::string_view) symbols[fun->name];
                     else
-                        obj.attr("name", nullptr);
+                        obj["name"] = nullptr;
                     if (auto pos = positions[fun->pos]) {
-                        obj.attr("file", (std::string_view) pos.file);
-                        obj.attr("line", pos.line);
-                        obj.attr("column", pos.column);
+                        if (auto path = std::get_if<Path>(&pos.origin))
+                            obj["file"] = *path;
+                        obj["line"] = pos.line;
+                        obj["column"] = pos.column;
                     }
-                    obj.attr("count", count);
+                    obj["count"] = count;
+                    list.push_back(obj);
                 }
             }
             {
-                auto list = topObj.list("attributes");
+                auto list = topObj["attributes"];
+                list = json::array();
                 for (auto & i : attrSelects) {
-                    auto obj = list.object();
+                    json obj = json::object();
                     if (auto pos = positions[i.first]) {
-                        obj.attr("file", (const std::string &) pos.file);
-                        obj.attr("line", pos.line);
-                        obj.attr("column", pos.column);
+                        if (auto path = std::get_if<Path>(&pos.origin))
+                            obj["file"] = *path;
+                        obj["line"] = pos.line;
+                        obj["column"] = pos.column;
                     }
-                    obj.attr("count", i.second);
+                    obj["count"] = i.second;
+                    list.push_back(obj);
                 }
             }
         }
 
         if (getEnv("NIX_SHOW_SYMBOLS").value_or("0") != "0") {
-            auto list = topObj.list("symbols");
-            symbols.dump([&](const std::string & s) { list.elem(s); });
+            // XXX: overrides earlier assignment
+            topObj["symbols"] = json::array();
+            auto &list = topObj["symbols"];
+            symbols.dump([&](const std::string & s) { list.emplace_back(s); });
+        }
+        if (outPath == "-") {
+            std::cerr << topObj.dump(2) << std::endl;
+        } else {
+            fs << topObj.dump(2) << std::endl;
         }
     }
 }
@@ -2585,6 +2562,23 @@ Strings EvalSettings::getDefaultNixPath()
     return res;
 }
 
+bool EvalSettings::isPseudoUrl(std::string_view s)
+{
+    if (s.compare(0, 8, "channel:") == 0) return true;
+    size_t pos = s.find("://");
+    if (pos == std::string::npos) return false;
+    std::string scheme(s, 0, pos);
+    return scheme == "http" || scheme == "https" || scheme == "file" || scheme == "channel" || scheme == "git" || scheme == "s3" || scheme == "ssh";
+}
+
+std::string EvalSettings::resolvePseudoUrl(std::string_view url)
+{
+    if (hasPrefix(url, "channel:"))
+        return "https://nixos.org/channels/" + std::string(url.substr(8)) + "/nixexprs.tar.xz";
+    else
+        return std::string(url);
+}
+
 EvalSettings evalSettings;
 
 static GlobalConfig::Register rEvalSettings(&evalSettings);

src/libexpr/eval.hh

@@ -60,7 +60,6 @@ void copyContext(const Value & v, PathSet & context);
 typedef std::map<Path, StorePath> SrcToStore;
 
 
-std::ostream & printValue(const EvalState & state, std::ostream & str, const Value & v);
 std::string printValue(const EvalState & state, const Value & v);
 std::ostream & operator << (std::ostream & os, const ValueType t);
 
@@ -78,7 +77,7 @@ struct RegexCache;
 std::shared_ptr<RegexCache> makeRegexCache();
 
 struct DebugTrace {
-    std::optional<ErrPos> pos;
+    std::shared_ptr<AbstractPos> pos;
     const Expr & expr;
     const Env & env;
     hintformat hint;
@@ -400,7 +399,7 @@ public:
         bool coerceMore = false, bool copyToStore = true,
         bool canonicalizePath = true);
 
-    std::string copyPathToStore(PathSet & context, const Path & path);
+    StorePath copyPathToStore(PathSet & context, const Path & path);
 
     /* Path coercion.  Converts strings, paths and derivations to a
        path.  The result is guaranteed to be a canonicalised, absolute
@@ -457,8 +456,12 @@ private:
     friend struct ExprAttrs;
     friend struct ExprLet;
 
-    Expr * parse(char * text, size_t length, FileOrigin origin, const PathView path,
-        const PathView basePath, std::shared_ptr<StaticEnv> & staticEnv);
+    Expr * parse(
+        char * text,
+        size_t length,
+        Pos::Origin origin,
+        Path basePath,
+        std::shared_ptr<StaticEnv> & staticEnv);
 
 public:
 
@@ -568,10 +571,6 @@ struct DebugTraceStacker {
 std::string_view showType(ValueType type);
 std::string showType(const Value & v);
 
-/* Decode a context string ‘!<name>!<path>’ into a pair <path,
-   name>. */
-NixStringContextElem decodeContext(const Store & store, std::string_view s);
-
 /* If `path' refers to a directory, then append "/default.nix". */
 Path resolveExprPath(Path path);
 
@@ -590,6 +589,10 @@ struct EvalSettings : Config
 
     static Strings getDefaultNixPath();
 
+    static bool isPseudoUrl(std::string_view s);
+
+    static std::string resolvePseudoUrl(std::string_view url);
+
     Setting<bool> enableNativeCode{this, false, "allow-unsafe-native-code-during-evaluation",
         "Whether builtin functions that allow executing native code should be enabled."};
 

src/libexpr/flake/call-flake.nix

@@ -43,7 +43,7 @@ let
 
           outputs = flake.outputs (inputs // { self = result; });
 
-          result = outputs // sourceInfo // { inherit inputs; inherit outputs; inherit sourceInfo; };
+          result = outputs // sourceInfo // { inherit inputs; inherit outputs; inherit sourceInfo; _type = "flake"; };
         in
           if node.flake or true then
             assert builtins.isFunction flake.outputs;

src/libexpr/flake/config.cc

@@ -56,7 +56,7 @@ void ConfigFile::apply()
             auto tlname = get(trustedList, name);
             if (auto saved = tlname ? get(*tlname, valueS) : nullptr) {
                 trusted = *saved;
-                warn("Using saved setting for '%s = %s' from ~/.local/share/nix/trusted-settings.json.", name,valueS);
+                printInfo("Using saved setting for '%s = %s' from ~/.local/share/nix/trusted-settings.json.", name, valueS);
             } else {
                 // FIXME: filter ANSI escapes, newlines, \r, etc.
                 if (std::tolower(logger->ask(fmt("do you want to allow configuration setting '%s' to be set to '" ANSI_RED "%s" ANSI_NORMAL "' (y/N)?", name, valueS)).value_or('n')) == 'y') {

src/libexpr/flake/flake.cc

@@ -143,7 +143,7 @@ static FlakeInput parseFlakeInput(EvalState & state,
         } catch (Error & e) {
             e.addTrace(
                 state.positions[attr.pos],
-                hintfmt("in flake attribute '%s'", state.symbols[attr.name]));
+                hintfmt("while evaluating flake attribute '%s'", state.symbols[attr.name]));
             throw;
         }
     }
@@ -152,7 +152,7 @@ static FlakeInput parseFlakeInput(EvalState & state,
         try {
             input.ref = FlakeRef::fromAttrs(attrs);
         } catch (Error & e) {
-            e.addTrace(state.positions[pos], hintfmt("in flake input"));
+            e.addTrace(state.positions[pos], hintfmt("while evaluating flake input"));
             throw;
         }
     else {
@@ -220,7 +220,7 @@ static Flake getFlake(
     Value vInfo;
     state.evalFile(flakeFile, vInfo, true); // FIXME: symlink attack
 
-    expectType(state, nAttrs, vInfo, state.positions.add({flakeFile, foFile}, 0, 0));
+    expectType(state, nAttrs, vInfo, state.positions.add({flakeFile}, 1, 1));
 
     if (auto description = vInfo.attrs->get(state.sDescription)) {
         expectType(state, nString, *description->value, description->pos);
@@ -353,7 +353,7 @@ LockedFlake lockFlake(
 
         std::function<void(
             const FlakeInputs & flakeInputs,
-            std::shared_ptr<Node> node,
+            ref<Node> node,
             const InputPath & inputPathPrefix,
             std::shared_ptr<const Node> oldNode,
             const InputPath & lockRootPath,
@@ -362,9 +362,15 @@ LockedFlake lockFlake(
             computeLocks;
 
         computeLocks = [&](
+            /* The inputs of this node, either from flake.nix or
+               flake.lock. */
             const FlakeInputs & flakeInputs,
-            std::shared_ptr<Node> node,
+            /* The node whose locks are to be updated.*/
+            ref<Node> node,
+            /* The path to this node in the lock file graph. */
             const InputPath & inputPathPrefix,
+            /* The old node, if any, from which locks can be
+               copied. */
             std::shared_ptr<const Node> oldNode,
             const InputPath & lockRootPath,
             const Path & parentPath,
@@ -452,7 +458,7 @@ LockedFlake lockFlake(
                         /* Copy the input from the old lock since its flakeref
                            didn't change and there is no override from a
                            higher level flake. */
-                        auto childNode = std::make_shared<LockedNode>(
+                        auto childNode = make_ref<LockedNode>(
                             oldLock->lockedRef, oldLock->originalRef, oldLock->isFlake);
 
                         node->inputs.insert_or_assign(id, childNode);
@@ -481,7 +487,7 @@ LockedFlake lockFlake(
                                         .isFlake = (*lockedNode)->isFlake,
                                     });
                                 } else if (auto follows = std::get_if<1>(&i.second)) {
-                                    if (! trustLock) {
+                                    if (!trustLock) {
                                         // It is possible that the flake has changed,
                                         // so we must confirm all the follows that are in the lock file are also in the flake.
                                         auto overridePath(inputPath);
@@ -521,8 +527,8 @@ LockedFlake lockFlake(
                            this input. */
                         debug("creating new input '%s'", inputPathS);
 
-                        if (!lockFlags.allowMutable && !input.ref->input.isLocked())
-                            throw Error("cannot update flake input '%s' in pure mode", inputPathS);
+                        if (!lockFlags.allowUnlocked && !input.ref->input.isLocked())
+                            throw Error("cannot update unlocked flake input '%s' in pure mode", inputPathS);
 
                         /* Note: in case of an --override-input, we use
                             the *original* ref (input2.ref) for the
@@ -544,7 +550,7 @@ LockedFlake lockFlake(
 
                             auto inputFlake = getFlake(state, localRef, useRegistries, flakeCache, inputPath);
 
-                            auto childNode = std::make_shared<LockedNode>(inputFlake.lockedRef, ref);
+                            auto childNode = make_ref<LockedNode>(inputFlake.lockedRef, ref);
 
                             node->inputs.insert_or_assign(id, childNode);
 
@@ -564,15 +570,19 @@ LockedFlake lockFlake(
                                 oldLock
                                 ? std::dynamic_pointer_cast<const Node>(oldLock)
                                 : LockFile::read(
-                                    inputFlake.sourceInfo->actualPath + "/" + inputFlake.lockedRef.subdir + "/flake.lock").root,
-                                oldLock ? lockRootPath : inputPath, localPath, false);
+                                    inputFlake.sourceInfo->actualPath + "/" + inputFlake.lockedRef.subdir + "/flake.lock").root.get_ptr(),
+                                oldLock ? lockRootPath : inputPath,
+                                localPath,
+                                false);
                         }
 
                         else {
                             auto [sourceInfo, resolvedRef, lockedRef] = fetchOrSubstituteTree(
                                 state, *input.ref, useRegistries, flakeCache);
-                            node->inputs.insert_or_assign(id,
-                                std::make_shared<LockedNode>(lockedRef, ref, false));
+
+                            auto childNode = make_ref<LockedNode>(lockedRef, ref, false);
+
+                            node->inputs.insert_or_assign(id, childNode);
                         }
                     }
 
@@ -587,8 +597,13 @@ LockedFlake lockFlake(
         auto parentPath = canonPath(flake.sourceInfo->actualPath + "/" + flake.lockedRef.subdir, true);
 
         computeLocks(
-            flake.inputs, newLockFile.root, {},
-            lockFlags.recreateLockFile ? nullptr : oldLockFile.root, {}, parentPath, false);
+            flake.inputs,
+            newLockFile.root,
+            {},
+            lockFlags.recreateLockFile ? nullptr : oldLockFile.root.get_ptr(),
+            {},
+            parentPath,
+            false);
 
         for (auto & i : lockFlags.inputOverrides)
             if (!overridesUsed.count(i.first))
@@ -611,9 +626,9 @@ LockedFlake lockFlake(
 
             if (lockFlags.writeLockFile) {
                 if (auto sourcePath = topRef.input.getSourcePath()) {
-                    if (!newLockFile.isImmutable()) {
+                    if (auto unlockedInput = newLockFile.isUnlocked()) {
                         if (fetchSettings.warnDirty)
-                            warn("will not write lock file of flake '%s' because it has a mutable input", topRef);
+                            warn("will not write lock file of flake '%s' because it has an unlocked input ('%s')", topRef, *unlockedInput);
                     } else {
                         if (!lockFlags.updateLockFile)
                             throw Error("flake '%s' requires lock file changes but they're not allowed due to '--no-update-lock-file'", topRef);
@@ -737,7 +752,7 @@ static void prim_getFlake(EvalState & state, const PosIdx pos, Value * * args, V
                 .updateLockFile = false,
                 .writeLockFile = false,
                 .useRegistries = !evalSettings.pureEval && fetchSettings.useRegistries,
-                .allowMutable  = !evalSettings.pureEval,
+                .allowUnlocked = !evalSettings.pureEval,
             }),
         v);
 }

src/libexpr/flake/flake.hh

@@ -108,11 +108,11 @@ struct LockFlags
 
     bool applyNixConfig = false;
 
-    /* Whether mutable flake references (i.e. those without a Git
+    /* Whether unlocked flake references (i.e. those without a Git
        revision or similar) without a corresponding lock are
-       allowed. Mutable flake references with a lock are always
+       allowed. Unlocked flake references with a lock are always
        allowed. */
-    bool allowMutable = true;
+    bool allowUnlocked = true;
 
     /* Whether to commit changes to flake.lock. */
     bool commitLockFile = false;

src/libexpr/flake/flakeref.cc

@@ -238,15 +238,15 @@ std::pair<fetchers::Tree, FlakeRef> FlakeRef::fetchTree(ref<Store> store) const
     return {std::move(tree), FlakeRef(std::move(lockedInput), subdir)};
 }
 
-std::tuple<FlakeRef, std::string, OutputsSpec> parseFlakeRefWithFragmentAndOutputsSpec(
+std::tuple<FlakeRef, std::string, ExtendedOutputsSpec> parseFlakeRefWithFragmentAndExtendedOutputsSpec(
     const std::string & url,
     const std::optional<Path> & baseDir,
     bool allowMissing,
     bool isFlake)
 {
-    auto [prefix, outputsSpec] = parseOutputsSpec(url);
-    auto [flakeRef, fragment] = parseFlakeRefWithFragment(prefix, baseDir, allowMissing, isFlake);
-    return {std::move(flakeRef), fragment, outputsSpec};
+    auto [prefix, extendedOutputsSpec] = ExtendedOutputsSpec::parse(url);
+    auto [flakeRef, fragment] = parseFlakeRefWithFragment(std::string { prefix }, baseDir, allowMissing, isFlake);
+    return {std::move(flakeRef), fragment, extendedOutputsSpec};
 }
 
 }

src/libexpr/flake/flakeref.hh

@@ -3,7 +3,7 @@
 #include "types.hh"
 #include "hash.hh"
 #include "fetchers.hh"
-#include "path-with-outputs.hh"
+#include "outputs-spec.hh"
 
 #include <variant>
 
@@ -35,7 +35,7 @@ typedef std::string FlakeId;
 
 struct FlakeRef
 {
-    /* fetcher-specific representation of the input, sufficient to
+    /* Fetcher-specific representation of the input, sufficient to
        perform the fetch operation. */
     fetchers::Input input;
 
@@ -80,7 +80,7 @@ std::pair<FlakeRef, std::string> parseFlakeRefWithFragment(
 std::optional<std::pair<FlakeRef, std::string>> maybeParseFlakeRefWithFragment(
     const std::string & url, const std::optional<Path> & baseDir = {});
 
-std::tuple<FlakeRef, std::string, OutputsSpec> parseFlakeRefWithFragmentAndOutputsSpec(
+std::tuple<FlakeRef, std::string, ExtendedOutputsSpec> parseFlakeRefWithFragmentAndExtendedOutputsSpec(
     const std::string & url,
     const std::optional<Path> & baseDir = {},
     bool allowMissing = false,

src/libexpr/flake/lockfile.cc

@@ -31,7 +31,7 @@ FlakeRef getFlakeRef(
 }
 
 LockedNode::LockedNode(const nlohmann::json & json)
-    : lockedRef(getFlakeRef(json, "locked", "info"))
+    : lockedRef(getFlakeRef(json, "locked", "info")) // FIXME: remove "info"
     , originalRef(getFlakeRef(json, "original", nullptr))
     , isFlake(json.find("flake") != json.end() ? (bool) json["flake"] : true)
 {
@@ -49,15 +49,15 @@ std::shared_ptr<Node> LockFile::findInput(const InputPath & path)
 {
     auto pos = root;
 
-    if (!pos) return {};
-
     for (auto & elem : path) {
         if (auto i = get(pos->inputs, elem)) {
             if (auto node = std::get_if<0>(&*i))
                 pos = *node;
             else if (auto follows = std::get_if<1>(&*i)) {
-                pos = findInput(*follows);
-                if (!pos) return {};
+                if (auto p = findInput(*follows))
+                    pos = ref(p);
+                else
+                    return {};
             }
         } else
             return {};
@@ -72,7 +72,7 @@ LockFile::LockFile(const nlohmann::json & json, const Path & path)
     if (version < 5 || version > 7)
         throw Error("lock file '%s' has unsupported version %d", path, version);
 
-    std::unordered_map<std::string, std::shared_ptr<Node>> nodeMap;
+    std::map<std::string, ref<Node>> nodeMap;
 
     std::function<void(Node & node, const nlohmann::json & jsonNode)> getInputs;
 
@@ -93,12 +93,12 @@ LockFile::LockFile(const nlohmann::json & json, const Path & path)
                     auto jsonNode2 = nodes.find(inputKey);
                     if (jsonNode2 == nodes.end())
                         throw Error("lock file references missing node '%s'", inputKey);
-                    auto input = std::make_shared<LockedNode>(*jsonNode2);
+                    auto input = make_ref<LockedNode>(*jsonNode2);
                     k = nodeMap.insert_or_assign(inputKey, input).first;
                     getInputs(*input, *jsonNode2);
                 }
-                if (auto child = std::dynamic_pointer_cast<LockedNode>(k->second))
-                    node.inputs.insert_or_assign(i.key(), child);
+                if (auto child = k->second.dynamic_pointer_cast<LockedNode>())
+                    node.inputs.insert_or_assign(i.key(), ref(child));
                 else
                     // FIXME: replace by follows node
                     throw Error("lock file contains cycle to root node");
@@ -122,9 +122,9 @@ nlohmann::json LockFile::toJSON() const
     std::unordered_map<std::shared_ptr<const Node>, std::string> nodeKeys;
     std::unordered_set<std::string> keys;
 
-    std::function<std::string(const std::string & key, std::shared_ptr<const Node> node)> dumpNode;
+    std::function<std::string(const std::string & key, ref<const Node> node)> dumpNode;
 
-    dumpNode = [&](std::string key, std::shared_ptr<const Node> node) -> std::string
+    dumpNode = [&](std::string key, ref<const Node> node) -> std::string
     {
         auto k = nodeKeys.find(node);
         if (k != nodeKeys.end())
@@ -159,10 +159,11 @@ nlohmann::json LockFile::toJSON() const
             n["inputs"] = std::move(inputs);
         }
 
-        if (auto lockedNode = std::dynamic_pointer_cast<const LockedNode>(node)) {
+        if (auto lockedNode = node.dynamic_pointer_cast<const LockedNode>()) {
             n["original"] = fetchers::attrsToJSON(lockedNode->originalRef.toAttrs());
             n["locked"] = fetchers::attrsToJSON(lockedNode->lockedRef.toAttrs());
-            if (!lockedNode->isFlake) n["flake"] = false;
+            if (!lockedNode->isFlake)
+                n["flake"] = false;
         }
 
         nodes[key] = std::move(n);
@@ -201,13 +202,13 @@ void LockFile::write(const Path & path) const
     writeFile(path, fmt("%s\n", *this));
 }
 
-bool LockFile::isImmutable() const
+std::optional<FlakeRef> LockFile::isUnlocked() const
 {
-    std::unordered_set<std::shared_ptr<const Node>> nodes;
+    std::set<ref<const Node>> nodes;
 
-    std::function<void(std::shared_ptr<const Node> node)> visit;
+    std::function<void(ref<const Node> node)> visit;
 
-    visit = [&](std::shared_ptr<const Node> node)
+    visit = [&](ref<const Node> node)
     {
         if (!nodes.insert(node).second) return;
         for (auto & i : node->inputs)
@@ -219,11 +220,12 @@ bool LockFile::isImmutable() const
 
     for (auto & i : nodes) {
         if (i == root) continue;
-        auto lockedNode = std::dynamic_pointer_cast<const LockedNode>(i);
-        if (lockedNode && !lockedNode->lockedRef.input.isLocked()) return false;
+        auto node = i.dynamic_pointer_cast<const LockedNode>();
+        if (node && !node->lockedRef.input.isLocked())
+            return node->lockedRef;
     }
 
-    return true;
+    return {};
 }
 
 bool LockFile::operator ==(const LockFile & other) const
@@ -247,12 +249,12 @@ InputPath parseInputPath(std::string_view s)
 
 std::map<InputPath, Node::Edge> LockFile::getAllInputs() const
 {
-    std::unordered_set<std::shared_ptr<Node>> done;
+    std::set<ref<Node>> done;
     std::map<InputPath, Node::Edge> res;
 
-    std::function<void(const InputPath & prefix, std::shared_ptr<Node> node)> recurse;
+    std::function<void(const InputPath & prefix, ref<Node> node)> recurse;
 
-    recurse = [&](const InputPath & prefix, std::shared_ptr<Node> node)
+    recurse = [&](const InputPath & prefix, ref<Node> node)
     {
         if (!done.insert(node).second) return;
 

src/libexpr/flake/lockfile.hh

@@ -20,7 +20,7 @@ struct LockedNode;
    type LockedNode. */
 struct Node : std::enable_shared_from_this<Node>
 {
-    typedef std::variant<std::shared_ptr<LockedNode>, InputPath> Edge;
+    typedef std::variant<ref<LockedNode>, InputPath> Edge;
 
     std::map<FlakeId, Edge> inputs;
 
@@ -47,11 +47,13 @@ struct LockedNode : Node
 
 struct LockFile
 {
-    std::shared_ptr<Node> root = std::make_shared<Node>();
+    ref<Node> root = make_ref<Node>();
 
     LockFile() {};
     LockFile(const nlohmann::json & json, const Path & path);
 
+    typedef std::map<ref<const Node>, std::string> KeyMap;
+
     nlohmann::json toJSON() const;
 
     std::string to_string() const;
@@ -60,7 +62,8 @@ struct LockFile
 
     void write(const Path & path) const;
 
-    bool isImmutable() const;
+    /* Check whether this lock file has any unlocked inputs. */
+    std::optional<FlakeRef> isUnlocked() const;
 
     bool operator ==(const LockFile & other) const;
 

src/libexpr/get-drvs.cc

@@ -150,7 +150,7 @@ DrvInfo::Outputs DrvInfo::queryOutputs(bool withPaths, bool onlyOutputsToInstall
         /* Check for `meta.outputsToInstall` and return `outputs` reduced to that. */
         const Value * outTI = queryMeta("outputsToInstall");
         if (!outTI) return outputs;
-        const auto errMsg = Error("this derivation has bad 'meta.outputsToInstall'");
+        auto errMsg = Error("this derivation has bad 'meta.outputsToInstall'");
             /* ^ this shows during `nix-env -i` right under the bad derivation */
         if (!outTI->isList()) throw errMsg;
         Outputs result;

src/libexpr/local.mk

@@ -6,6 +6,7 @@ libexpr_DIR := $(d)
 
 libexpr_SOURCES := \
   $(wildcard $(d)/*.cc) \
+  $(wildcard $(d)/value/*.cc) \
   $(wildcard $(d)/primops/*.cc) \
   $(wildcard $(d)/flake/*.cc) \
   $(d)/lexer-tab.cc \
@@ -37,6 +38,8 @@ clean-files += $(d)/parser-tab.cc $(d)/parser-tab.hh $(d)/lexer-tab.cc $(d)/lexe
 
 $(eval $(call install-file-in, $(d)/nix-expr.pc, $(libdir)/pkgconfig, 0644))
 
+$(foreach i, $(wildcard src/libexpr/value/*.hh), \
+  $(eval $(call install-file-in, $(i), $(includedir)/nix/value, 0644)))
 $(foreach i, $(wildcard src/libexpr/flake/*.hh), \
   $(eval $(call install-file-in, $(i), $(includedir)/nix/flake, 0644)))
 

src/libexpr/nixexpr.cc

@@ -8,6 +8,58 @@
 
 namespace nix {
 
+struct PosAdapter : AbstractPos
+{
+    Pos::Origin origin;
+
+    PosAdapter(Pos::Origin origin)
+        : origin(std::move(origin))
+    {
+    }
+
+    std::optional<std::string> getSource() const override
+    {
+        return std::visit(overloaded {
+            [](const Pos::none_tag &) -> std::optional<std::string> {
+                return std::nullopt;
+            },
+            [](const Pos::Stdin & s) -> std::optional<std::string> {
+                // Get rid of the null terminators added by the parser.
+                return std::string(s.source->c_str());
+            },
+            [](const Pos::String & s) -> std::optional<std::string> {
+                // Get rid of the null terminators added by the parser.
+                return std::string(s.source->c_str());
+            },
+            [](const Path & path) -> std::optional<std::string> {
+                try {
+                    return readFile(path);
+                } catch (Error &) {
+                    return std::nullopt;
+                }
+            }
+        }, origin);
+    }
+
+    void print(std::ostream & out) const override
+    {
+        std::visit(overloaded {
+            [&](const Pos::none_tag &) { out << "«none»"; },
+            [&](const Pos::Stdin &) { out << "«stdin»"; },
+            [&](const Pos::String & s) { out << "«string»"; },
+            [&](const Path & path) { out << path; }
+        }, origin);
+    }
+};
+
+Pos::operator std::shared_ptr<AbstractPos>() const
+{
+    auto pos = std::make_shared<PosAdapter>(origin);
+    pos->line = line;
+    pos->column = column;
+    return pos;
+}
+
 /* Displaying abstract syntax trees. */
 
 static void showString(std::ostream & str, std::string_view s)
@@ -248,24 +300,10 @@ void ExprPos::show(const SymbolTable & symbols, std::ostream & str) const
 
 std::ostream & operator << (std::ostream & str, const Pos & pos)
 {
-    if (!pos)
+    if (auto pos2 = (std::shared_ptr<AbstractPos>) pos) {
+        str << *pos2;
+    } else
         str << "undefined position";
-    else
-    {
-        auto f = format(ANSI_BOLD "%1%" ANSI_NORMAL ":%2%:%3%");
-        switch (pos.origin) {
-            case foFile:
-                f % (const std::string &) pos.file;
-                break;
-            case foStdin:
-            case foString:
-                f % "(string)";
-                break;
-            default:
-                throw Error("unhandled Pos origin!");
-        }
-        str << (f % pos.line % pos.column).str();
-    }
 
     return str;
 }
@@ -289,7 +327,6 @@ std::string showAttrPath(const SymbolTable & symbols, const AttrPath & attrPath)
 }
 
 
-
 /* Computing levels/displacements for variables. */
 
 void Expr::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)

src/libexpr/nixexpr.hh

@@ -23,15 +23,22 @@ MakeError(MissingArgumentError, EvalError);
 MakeError(RestrictedPathError, Error);
 
 /* Position objects. */
-
 struct Pos
 {
-    std::string file;
-    FileOrigin origin;
     uint32_t line;
     uint32_t column;
 
+    struct none_tag { };
+    struct Stdin { ref<std::string> source; };
+    struct String { ref<std::string> source; };
+
+    typedef std::variant<none_tag, Stdin, String, Path> Origin;
+
+    Origin origin;
+
     explicit operator bool() const { return line > 0; }
+
+    operator std::shared_ptr<AbstractPos>() const;
 };
 
 class PosIdx {
@@ -47,7 +54,11 @@ public:
 
     explicit operator bool() const { return id > 0; }
 
-    bool operator<(const PosIdx other) const { return id < other.id; }
+    bool operator <(const PosIdx other) const { return id < other.id; }
+
+    bool operator ==(const PosIdx other) const { return id == other.id; }
+
+    bool operator !=(const PosIdx other) const { return id != other.id; }
 };
 
 class PosTable
@@ -61,13 +72,13 @@ public:
         // current origins.back() can be reused or not.
         mutable uint32_t idx = std::numeric_limits<uint32_t>::max();
 
-        explicit Origin(uint32_t idx): idx(idx), file{}, origin{} {}
+        // Used for searching in PosTable::[].
+        explicit Origin(uint32_t idx): idx(idx), origin{Pos::none_tag()} {}
 
     public:
-        const std::string file;
-        const FileOrigin origin;
+        const Pos::Origin origin;
 
-        Origin(std::string file, FileOrigin origin): file(std::move(file)), origin(origin) {}
+        Origin(Pos::Origin origin): origin(origin) {}
     };
 
     struct Offset {
@@ -107,7 +118,7 @@ public:
             [] (const auto & a, const auto & b) { return a.idx < b.idx; });
         const auto origin = *std::prev(pastOrigin);
         const auto offset = offsets[idx];
-        return {origin.file, origin.origin, offset.line, offset.column};
+        return {offset.line, offset.column, origin.origin};
     }
 };
 

src/libexpr/parser.y

@@ -34,11 +34,6 @@ namespace nix {
         Path basePath;
         PosTable::Origin origin;
         std::optional<ErrorInfo> error;
-        ParseData(EvalState & state, PosTable::Origin origin)
-            : state(state)
-            , symbols(state.symbols)
-            , origin(std::move(origin))
-            { };
     };
 
     struct ParserFormals {
@@ -643,29 +638,26 @@ formal
 #include "filetransfer.hh"
 #include "fetchers.hh"
 #include "store-api.hh"
+#include "flake/flake.hh"
 
 
 namespace nix {
 
 
-Expr * EvalState::parse(char * text, size_t length, FileOrigin origin,
-    const PathView path, const PathView basePath, std::shared_ptr<StaticEnv> & staticEnv)
+Expr * EvalState::parse(
+    char * text,
+    size_t length,
+    Pos::Origin origin,
+    Path basePath,
+    std::shared_ptr<StaticEnv> & staticEnv)
 {
     yyscan_t scanner;
-    std::string file;
-    switch (origin) {
-        case foFile:
-            file = path;
-            break;
-        case foStdin:
-        case foString:
-            file = text;
-            break;
-        default:
-            assert(false);
-    }
-    ParseData data(*this, {file, origin});
-    data.basePath = basePath;
+    ParseData data {
+        .state = *this,
+        .symbols = symbols,
+        .basePath = std::move(basePath),
+        .origin = {origin},
+    };
 
     yylex_init(&scanner);
     yy_scan_buffer(text, length, scanner);
@@ -717,14 +709,15 @@ Expr * EvalState::parseExprFromFile(const Path & path, std::shared_ptr<StaticEnv
     auto buffer = readFile(path);
     // readFile should have left some extra space for terminators
     buffer.append("\0\0", 2);
-    return parse(buffer.data(), buffer.size(), foFile, path, dirOf(path), staticEnv);
+    return parse(buffer.data(), buffer.size(), path, dirOf(path), staticEnv);
 }
 
 
-Expr * EvalState::parseExprFromString(std::string s, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv)
+Expr * EvalState::parseExprFromString(std::string s_, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv)
 {
-    s.append("\0\0", 2);
-    return parse(s.data(), s.size(), foString, "", basePath, staticEnv);
+    auto s = make_ref<std::string>(std::move(s_));
+    s->append("\0\0", 2);
+    return parse(s->data(), s->size(), Pos::String{.source = s}, basePath, staticEnv);
 }
 
 
@@ -740,7 +733,8 @@ Expr * EvalState::parseStdin()
     auto buffer = drainFD(0);
     // drainFD should have left some extra space for terminators
     buffer.append("\0\0", 2);
-    return parse(buffer.data(), buffer.size(), foStdin, "", absPath("."), staticBaseEnv);
+    auto s = make_ref<std::string>(std::move(buffer));
+    return parse(s->data(), s->size(), Pos::Stdin{.source = s}, absPath("."), staticBaseEnv);
 }
 
 
@@ -805,17 +799,28 @@ std::pair<bool, std::string> EvalState::resolveSearchPathElem(const SearchPathEl
 
     std::pair<bool, std::string> res;
 
-    if (isUri(elem.second)) {
+    if (EvalSettings::isPseudoUrl(elem.second)) {
         try {
-            res = { true, store->toRealPath(fetchers::downloadTarball(
-                        store, resolveUri(elem.second), "source", false).first.storePath) };
+            auto storePath = fetchers::downloadTarball(
+                store, EvalSettings::resolvePseudoUrl(elem.second), "source", false).first.storePath;
+            res = { true, store->toRealPath(storePath) };
         } catch (FileTransferError & e) {
             logWarning({
                 .msg = hintfmt("Nix search path entry '%1%' cannot be downloaded, ignoring", elem.second)
             });
             res = { false, "" };
         }
-    } else {
+    }
+
+    else if (hasPrefix(elem.second, "flake:")) {
+        settings.requireExperimentalFeature(Xp::Flakes);
+        auto flakeRef = parseFlakeRef(elem.second.substr(6), {}, true, false);
+        debug("fetching flake search path element '%s''", elem.second);
+        auto storePath = flakeRef.resolve(store).fetchTree(store).first.storePath;
+        res = { true, store->toRealPath(storePath) };
+    }
+
+    else {
         auto path = absPath(elem.second);
         if (pathExists(path))
             res = { true, path };

src/libexpr/primops.cc

@@ -5,14 +5,15 @@
 #include "globals.hh"
 #include "json-to-value.hh"
 #include "names.hh"
+#include "references.hh"
 #include "store-api.hh"
 #include "util.hh"
-#include "json.hh"
 #include "value-to-json.hh"
 #include "value-to-xml.hh"
 #include "primops.hh"
 
 #include <boost/container/small_vector.hpp>
+#include <nlohmann/json.hpp>
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -42,16 +43,32 @@ StringMap EvalState::realiseContext(const PathSet & context)
     std::vector<DerivedPath::Built> drvs;
     StringMap res;
 
-    for (auto & i : context) {
-        auto [ctx, outputName] = decodeContext(*store, i);
-        auto ctxS = store->printStorePath(ctx);
-        if (!store->isValidPath(ctx))
-            debugThrowLastTrace(InvalidPathError(store->printStorePath(ctx)));
-        if (!outputName.empty() && ctx.isDerivation()) {
-            drvs.push_back({ctx, {outputName}});
-        } else {
-            res.insert_or_assign(ctxS, ctxS);
-        }
+    for (auto & c_ : context) {
+        auto ensureValid = [&](const StorePath & p) {
+            if (!store->isValidPath(p))
+                debugThrowLastTrace(InvalidPathError(store->printStorePath(p)));
+        };
+        auto c = NixStringContextElem::parse(*store, c_);
+        std::visit(overloaded {
+            [&](const NixStringContextElem::Built & b) {
+                drvs.push_back(DerivedPath::Built {
+                    .drvPath = b.drvPath,
+                    .outputs = OutputsSpec::Names { b.output },
+                });
+                ensureValid(b.drvPath);
+            },
+            [&](const NixStringContextElem::Opaque & o) {
+                auto ctxS = store->printStorePath(o.path);
+                res.insert_or_assign(ctxS, ctxS);
+                ensureValid(o.path);
+            },
+            [&](const NixStringContextElem::DrvDeep & d) {
+                /* Treat same as Opaque */
+                auto ctxS = store->printStorePath(d.drvPath);
+                res.insert_or_assign(ctxS, ctxS);
+                ensureValid(d.drvPath);
+            },
+        }, c.raw());
     }
 
     if (drvs.empty()) return {};
@@ -67,16 +84,12 @@ StringMap EvalState::realiseContext(const PathSet & context)
     store->buildPaths(buildReqs);
 
     /* Get all the output paths corresponding to the placeholders we had */
-    for (auto & [drvPath, outputs] : drvs) {
-        const auto outputPaths = store->queryDerivationOutputMap(drvPath);
-        for (auto & outputName : outputs) {
-            auto outputPath = get(outputPaths, outputName);
-            if (!outputPath)
-                debugThrowLastTrace(Error("derivation '%s' does not have an output named '%s'",
-                    store->printStorePath(drvPath), outputName));
+    for (auto & drv : drvs) {
+        auto outputs = resolveDerivedPath(*store, drv);
+        for (auto & [outputName, outputPath] : outputs) {
             res.insert_or_assign(
-                downstreamPlaceholder(*store, drvPath, outputName),
-                store->printStorePath(*outputPath)
+                downstreamPlaceholder(*store, drv.drvPath, outputName),
+                store->printStorePath(outputPath)
             );
         }
     }
@@ -247,6 +260,7 @@ static RegisterPrimOp primop_scopedImport(RegisterPrimOp::Info {
 static RegisterPrimOp primop_import({
     .name = "import",
     .args = {"path"},
+    // TODO turn "normal path values" into link below
     .doc = R"(
       Load, parse and return the Nix expression in the file *path*. If
       *path* is a directory, the file ` default.nix ` in that directory
@@ -260,7 +274,7 @@ static RegisterPrimOp primop_import({
       >
       > Unlike some languages, `import` is a regular function in Nix.
       > Paths using the angle bracket syntax (e.g., `import` *\<foo\>*)
-      > are [normal path values](language-values.md).
+      > are normal [path values](@docroot@/language/values.md#type-path).
 
       A Nix expression loaded by `import` must not contain any *free
       variables* (identifiers that are not defined in the Nix expression
@@ -367,8 +381,7 @@ void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v)
     auto output = runProgram(program, true, commandArgs);
     Expr * parsed;
     try {
-        auto base = state.positions[pos];
-        parsed = state.parseExprFromString(std::move(output), base.file);
+        parsed = state.parseExprFromString(std::move(output), "/");
     } catch (Error & e) {
         e.addTrace(state.positions[pos], "While parsing the output from '%1%'", program);
         throw;
@@ -797,7 +810,7 @@ static void prim_addErrorContext(EvalState & state, const PosIdx pos, Value * *
         v = *args[1];
     } catch (Error & e) {
         PathSet context;
-        e.addTrace(std::nullopt, state.coerceToString(pos, *args[0], context).toOwned());
+        e.addTrace(nullptr, state.coerceToString(pos, *args[0], context).toOwned());
         throw;
     }
 }
@@ -1010,6 +1023,7 @@ static void prim_second(EvalState & state, const PosIdx pos, Value * * args, Val
    derivation. */
 static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * * args, Value & v)
 {
+    using nlohmann::json;
     state.forceAttrs(*args[0], pos);
 
     /* Figure out the name first (for stack backtraces). */
@@ -1031,11 +1045,10 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
     }
 
     /* Check whether attributes should be passed as a JSON file. */
-    std::ostringstream jsonBuf;
-    std::unique_ptr<JSONObject> jsonObject;
+    std::optional<json> jsonObject;
     attr = args[0]->attrs->find(state.sStructuredAttrs);
     if (attr != args[0]->attrs->end() && state.forceBool(*attr->value, pos))
-        jsonObject = std::make_unique<JSONObject>(jsonBuf);
+        jsonObject = json::object();
 
     /* Check whether null attributes should be ignored. */
     bool ignoreNulls = false;
@@ -1137,8 +1150,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
 
                     if (i->name == state.sStructuredAttrs) continue;
 
-                    auto placeholder(jsonObject->placeholder(key));
-                    printValueAsJSON(state, true, *i->value, pos, placeholder, context);
+                    (*jsonObject)[key] = printValueAsJSON(state, true, *i->value, pos, context);
 
                     if (i->name == state.sBuilder)
                         drv.builder = state.forceString(*i->value, context, posDrvName);
@@ -1182,42 +1194,38 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
     }
 
     if (jsonObject) {
+        drv.env.emplace("__json", jsonObject->dump());
         jsonObject.reset();
-        drv.env.emplace("__json", jsonBuf.str());
     }
 
     /* Everything in the context of the strings in the derivation
        attributes should be added as dependencies of the resulting
        derivation. */
-    for (auto & path : context) {
-
-        /* Paths marked with `=' denote that the path of a derivation
-           is explicitly passed to the builder.  Since that allows the
-           builder to gain access to every path in the dependency
-           graph of the derivation (including all outputs), all paths
-           in the graph must be added to this derivation's list of
-           inputs to ensure that they are available when the builder
-           runs. */
-        if (path.at(0) == '=') {
-            /* !!! This doesn't work if readOnlyMode is set. */
-            StorePathSet refs;
-            state.store->computeFSClosure(state.store->parseStorePath(std::string_view(path).substr(1)), refs);
-            for (auto & j : refs) {
-                drv.inputSrcs.insert(j);
-                if (j.isDerivation())
-                    drv.inputDrvs[j] = state.store->readDerivation(j).outputNames();
-            }
-        }
-
-        /* Handle derivation outputs of the form ‘!<name>!<path>’. */
-        else if (path.at(0) == '!') {
-            auto ctx = decodeContext(*state.store, path);
-            drv.inputDrvs[ctx.first].insert(ctx.second);
-        }
-
-        /* Otherwise it's a source file. */
-        else
-            drv.inputSrcs.insert(state.store->parseStorePath(path));
+    for (auto & c_ : context) {
+        auto c = NixStringContextElem::parse(*state.store, c_);
+        std::visit(overloaded {
+            /* Since this allows the builder to gain access to every
+               path in the dependency graph of the derivation (including
+               all outputs), all paths in the graph must be added to
+               this derivation's list of inputs to ensure that they are
+               available when the builder runs. */
+            [&](const NixStringContextElem::DrvDeep & d) {
+                /* !!! This doesn't work if readOnlyMode is set. */
+                StorePathSet refs;
+                state.store->computeFSClosure(d.drvPath, refs);
+                for (auto & j : refs) {
+                    drv.inputSrcs.insert(j);
+                    if (j.isDerivation())
+                        drv.inputDrvs[j] = state.store->readDerivation(j).outputNames();
+                }
+            },
+            [&](const NixStringContextElem::Built & b) {
+                drv.inputDrvs[b.drvPath].insert(b.output);
+            },
+            [&](const NixStringContextElem::Opaque & o) {
+                drv.inputSrcs.insert(o.path);
+            },
+        }, c.raw());
     }
 
     /* Do we have all required attributes? */
@@ -1461,10 +1469,10 @@ static RegisterPrimOp primop_storePath({
 static void prim_pathExists(EvalState & state, const PosIdx pos, Value * * args, Value & v)
 {
     /* We don’t check the path right now, because we don’t want to
-      throw if the path isn’t allowed, but just return false (and we
-      can’t just catch the exception here because we still want to
-      throw if something in the evaluation of `*args[0]` tries to
-      access an unauthorized path). */
+       throw if the path isn’t allowed, but just return false (and we
+       can’t just catch the exception here because we still want to
+       throw if something in the evaluation of `*args[0]` tries to
+       access an unauthorized path). */
     auto path = realisePath(state, pos, *args[0], { .checkForPureEval = false });
 
     try {
@@ -1542,6 +1550,10 @@ static void prim_readFile(EvalState & state, const PosIdx pos, Value * * args, V
             refs = state.store->queryPathInfo(state.store->toStorePath(path).first)->references;
         } catch (Error &) { // FIXME: should be InvalidPathError
         }
+        // Re-scan references to filter down to just the ones that actually occur in the file.
+        auto refsSink = PathRefScanSink::fromPaths(refs);
+        refsSink << s;
+        refs = refsSink.getResultPaths();
     }
     auto context = state.store->printStorePathSet(refs);
     v.mkString(s, context);
@@ -1883,8 +1895,7 @@ static RegisterPrimOp primop_toFile({
       path.  The file has suffix *name*. This file can be used as an
       input to derivations. One application is to write builders
       “inline”. For instance, the following Nix expression combines the
-      [Nix expression for GNU Hello](expression-syntax.md) and its
-      [build script](build-script.md) into one file:
+      Nix expression for GNU Hello and its build script into one file:
 
       ```nix
       { stdenv, fetchurl, perl }:
@@ -1927,8 +1938,8 @@ static RegisterPrimOp primop_toFile({
       ";
       ```
 
-      Note that `${configFile}` is an
-      [antiquotation](language-values.md), so the result of the
+      Note that `${configFile}` is a
+      [string interpolation](@docroot@/language/values.md#type-string), so the result of the
       expression `configFile`
       (i.e., a path like `/nix/store/m7p7jfny445k...-foo.conf`) will be
       spliced into the resulting string.
@@ -2416,12 +2427,18 @@ static RegisterPrimOp primop_listToAttrs({
       Construct a set from a list specifying the names and values of each
       attribute. Each element of the list should be a set consisting of a
       string-valued attribute `name` specifying the name of the attribute,
-      and an attribute `value` specifying its value. Example:
+      and an attribute `value` specifying its value.
+
+      In case of duplicate occurrences of the same name, the first
+      takes precedence.
+
+      Example:
 
       ```nix
       builtins.listToAttrs
         [ { name = "foo"; value = 123; }
           { name = "bar"; value = 456; }
+          { name = "bar"; value = 420; }
         ]
       ```
 
@@ -2439,12 +2456,62 @@ static void prim_intersectAttrs(EvalState & state, const PosIdx pos, Value * * a
     state.forceAttrs(*args[0], pos);
     state.forceAttrs(*args[1], pos);
 
-    auto attrs = state.buildBindings(std::min(args[0]->attrs->size(), args[1]->attrs->size()));
+    Bindings &left = *args[0]->attrs;
+    Bindings &right = *args[1]->attrs;
 
-    for (auto & i : *args[0]->attrs) {
-        Bindings::iterator j = args[1]->attrs->find(i.name);
-        if (j != args[1]->attrs->end())
-            attrs.insert(*j);
+    auto attrs = state.buildBindings(std::min(left.size(), right.size()));
+
+    // The current implementation has good asymptotic complexity and is reasonably
+    // simple. Further optimization may be possible, but does not seem productive,
+    // considering the state of eval performance in 2022.
+    //
+    // I have looked for reusable and/or standard solutions and these are my
+    // findings:
+    //
+    // STL
+    // ===
+    // std::set_intersection is not suitable, as it only performs a simultaneous
+    // linear scan; not taking advantage of random access. This is O(n + m), so
+    // linear in the largest set, which is not acceptable for callPackage in Nixpkgs.
+    //
+    // Simultaneous scan, with alternating simple binary search
+    // ===
+    // One alternative algorithm scans the attrsets simultaneously, jumping
+    // forward using `lower_bound` in case of inequality. This should perform
+    // well on very similar sets, having a local and predictable access pattern.
+    // On dissimilar sets, it seems to need more comparisons than the current
+    // algorithm, as few consecutive attrs match. `lower_bound` could take
+    // advantage of the decreasing remaining search space, but this causes
+    // the medians to move, which can mean that they don't stay in the cache
+    // like they would with the current naive `find`.
+    //
+    // Double binary search
+    // ===
+    // The optimal algorithm may be "Double binary search", which doesn't
+    // scan at all, but rather divides both sets simultaneously.
+    // See "Fast Intersection Algorithms for Sorted Sequences" by Baeza-Yates et al.
+    // https://cs.uwaterloo.ca/~ajsaling/papers/intersection_alg_app10.pdf
+    // The only downsides I can think of are not having a linear access pattern
+    // for similar sets, and having to maintain a more intricate algorithm.
+    //
+    // Adaptive
+    // ===
+    // Finally one could run try a simultaneous scan, count misses and fall back
+    // to double binary search when the counter hit some threshold and/or ratio.
+
+    if (left.size() < right.size()) {
+        for (auto & l : left) {
+            Bindings::iterator r = right.find(l.name);
+            if (r != right.end())
+                attrs.insert(*r);
+        }
+    }
+    else {
+        for (auto & r : right) {
+            Bindings::iterator l = left.find(r.name);
+            if (l != left.end())
+                attrs.insert(r);
+        }
     }
 
     v.mkAttrs(attrs.alreadySorted());
@@ -2456,6 +2523,8 @@ static RegisterPrimOp primop_intersectAttrs({
     .doc = R"(
       Return a set consisting of the attributes in the set *e2* which have the
       same name as some attribute in *e1*.
+
+      Performs in O(*n* log *m*) where *n* is the size of the smaller set and *m* the larger set's size.
     )",
     .fun = prim_intersectAttrs,
 });
@@ -3821,8 +3890,8 @@ static RegisterPrimOp primop_parseDrvName({
     .args = {"s"},
     .doc = R"(
       Split the string *s* into a package name and version. The package
-      name is everything up to but not including the first dash followed
-      by a digit, and the version is everything following that dash. The
+      name is everything up to but not including the first dash not followed
+      by a letter, and the version is everything following that dash. The
       result is returned in a set `{ name, version }`. Thus,
       `builtins.parseDrvName "nix-0.12pre12876"` returns `{ name =
       "nix"; version = "0.12pre12876"; }`.
@@ -4008,7 +4077,7 @@ void EvalState::createBaseEnv()
         // the parser needs two NUL bytes as terminators; one of them
         // is implied by being a C string.
         "\0";
-    eval(parse(code, sizeof(code), foFile, derivationNixPath, "/", staticBaseEnv), *vDerivation);
+    eval(parse(code, sizeof(code), derivationNixPath, "/", staticBaseEnv), *vDerivation);
 }
 
 

src/libexpr/primops/context.cc

@@ -37,8 +37,15 @@ static void prim_unsafeDiscardOutputDependency(EvalState & state, const PosIdx p
     auto s = state.coerceToString(pos, *args[0], context);
 
     PathSet context2;
-    for (auto & p : context)
-        context2.insert(p.at(0) == '=' ? std::string(p, 1) : p);
+    for (auto && p : context) {
+        auto c = NixStringContextElem::parse(*state.store, p);
+        if (auto * ptr = std::get_if<NixStringContextElem::DrvDeep>(&c)) {
+            context2.emplace(state.store->printStorePath(ptr->drvPath));
+        } else {
+            /* Can reuse original item */
+            context2.emplace(std::move(p));
+        }
+    }
 
     v.mkString(*s, context2);
 }
@@ -74,34 +81,20 @@ static void prim_getContext(EvalState & state, const PosIdx pos, Value * * args,
     };
     PathSet context;
     state.forceString(*args[0], context, pos);
-    auto contextInfos = std::map<Path, ContextInfo>();
+    auto contextInfos = std::map<StorePath, ContextInfo>();
     for (const auto & p : context) {
-        Path drv;
-        std::string output;
-        const Path * path = &p;
-        if (p.at(0) == '=') {
-            drv = std::string(p, 1);
-            path = &drv;
-        } else if (p.at(0) == '!') {
-            NixStringContextElem ctx = decodeContext(*state.store, p);
-            drv = state.store->printStorePath(ctx.first);
-            output = ctx.second;
-            path = &drv;
-        }
-        auto isPath = drv.empty();
-        auto isAllOutputs = (!drv.empty()) && output.empty();
-
-        auto iter = contextInfos.find(*path);
-        if (iter == contextInfos.end()) {
-            contextInfos.emplace(*path, ContextInfo{isPath, isAllOutputs, output.empty() ? Strings{} : Strings{std::move(output)}});
-        } else {
-            if (isPath)
-                iter->second.path = true;
-            else if (isAllOutputs)
-                iter->second.allOutputs = true;
-            else
-                iter->second.outputs.emplace_back(std::move(output));
-        }
+        NixStringContextElem ctx = NixStringContextElem::parse(*state.store, p);
+        std::visit(overloaded {
+            [&](NixStringContextElem::DrvDeep & d) {
+                contextInfos[d.drvPath].allOutputs = true;
+            },
+            [&](NixStringContextElem::Built & b) {
+                contextInfos[b.drvPath].outputs.emplace_back(std::move(b.output));
+            },
+            [&](NixStringContextElem::Opaque & o) {
+                contextInfos[o.path].path = true;
+            },
+        }, ctx.raw());
     }
 
     auto attrs = state.buildBindings(contextInfos.size());
@@ -120,7 +113,7 @@ static void prim_getContext(EvalState & state, const PosIdx pos, Value * * args,
             for (const auto & [i, output] : enumerate(info.second.outputs))
                 (outputsVal.listElems()[i] = state.allocValue())->mkString(output);
         }
-        attrs.alloc(info.first).mkAttrs(infoAttrs);
+        attrs.alloc(state.store->printStorePath(info.first)).mkAttrs(infoAttrs);
     }
 
     v.mkAttrs(attrs);

src/libexpr/primops/fetchTree.cc

@@ -220,7 +220,8 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
     } else
         url = state.forceStringNoCtx(*args[0], pos);
 
-    url = resolveUri(*url);
+    if (who == "fetchTarball")
+        url = evalSettings.resolvePseudoUrl(*url);
 
     state.checkURI(*url);
 

src/libexpr/tests/libexprtests.hh

@@ -12,6 +12,7 @@ namespace nix {
     class LibExprTest : public ::testing::Test {
         public:
             static void SetUpTestSuite() {
+                initLibStore();
                 initGC();
             }
 
@@ -123,7 +124,7 @@ namespace nix {
 
     MATCHER_P(IsAttrsOfSize, n, fmt("Is a set of size [%1%]", n)) {
         if (arg.type() != nAttrs) {
-            *result_listener << "Expexted set got " << arg.type();
+            *result_listener << "Expected set got " << arg.type();
             return false;
         } else if (arg.attrs->size() != (size_t)n) {
             *result_listener << "Expected a set with " << n << " attributes but got " << arg.attrs->size();

src/libexpr/tests/local.mk

@@ -6,7 +6,9 @@ libexpr-tests_DIR := $(d)
 
 libexpr-tests_INSTALL_DIR :=
 
-libexpr-tests_SOURCES := $(wildcard $(d)/*.cc)
+libexpr-tests_SOURCES := \
+    $(wildcard $(d)/*.cc) \
+    $(wildcard $(d)/value/*.cc)
 
 libexpr-tests_CXXFLAGS += -I src/libexpr -I src/libutil -I src/libstore -I src/libexpr/tests
 

src/libexpr/tests/primops.cc

@@ -151,20 +151,7 @@ namespace nix {
         // The `y` attribute is at position
         const char* expr = "builtins.unsafeGetAttrPos \"y\" { y = \"x\"; }";
         auto v = eval(expr);
-        ASSERT_THAT(v, IsAttrsOfSize(3));
-
-        auto file = v.attrs->find(createSymbol("file"));
-        ASSERT_NE(file, nullptr);
-        // FIXME: The file when running these tests is the input string?!?
-        ASSERT_THAT(*file->value, IsStringEq(expr));
-
-        auto line = v.attrs->find(createSymbol("line"));
-        ASSERT_NE(line, nullptr);
-        ASSERT_THAT(*line->value, IsIntEq(1));
-
-        auto column = v.attrs->find(createSymbol("column"));
-        ASSERT_NE(column, nullptr);
-        ASSERT_THAT(*column->value, IsIntEq(33));
+        ASSERT_THAT(v, IsNull());
     }
 
     TEST_F(PrimOpTest, hasAttr) {
@@ -617,7 +604,7 @@ namespace nix {
 
     TEST_F(PrimOpTest, storeDir) {
         auto v = eval("builtins.storeDir");
-        ASSERT_THAT(v, IsStringEq("/nix/store"));
+        ASSERT_THAT(v, IsStringEq(settings.nixStore));
     }
 
     TEST_F(PrimOpTest, nixVersion) {

src/libexpr/tests/value/context.cc

@@ -0,0 +1,72 @@
+#include "value/context.hh"
+
+#include "libexprtests.hh"
+
+namespace nix {
+
+// Testing of trivial expressions
+struct NixStringContextElemTest : public LibExprTest {
+   const Store & store() const {
+       return *LibExprTest::store;
+   }
+};
+
+TEST_F(NixStringContextElemTest, empty_invalid) {
+    EXPECT_THROW(
+        NixStringContextElem::parse(store(), ""),
+        BadNixStringContextElem);
+}
+
+TEST_F(NixStringContextElemTest, single_bang_invalid) {
+    EXPECT_THROW(
+        NixStringContextElem::parse(store(), "!"),
+        BadNixStringContextElem);
+}
+
+TEST_F(NixStringContextElemTest, double_bang_invalid) {
+    EXPECT_THROW(
+        NixStringContextElem::parse(store(), "!!/"),
+        BadStorePath);
+}
+
+TEST_F(NixStringContextElemTest, eq_slash_invalid) {
+    EXPECT_THROW(
+        NixStringContextElem::parse(store(), "=/"),
+        BadStorePath);
+}
+
+TEST_F(NixStringContextElemTest, slash_invalid) {
+    EXPECT_THROW(
+        NixStringContextElem::parse(store(), "/"),
+        BadStorePath);
+}
+
+TEST_F(NixStringContextElemTest, opaque) {
+    std::string_view opaque = "/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x";
+    auto elem = NixStringContextElem::parse(store(), opaque);
+    auto * p = std::get_if<NixStringContextElem::Opaque>(&elem);
+    ASSERT_TRUE(p);
+    ASSERT_EQ(p->path, store().parseStorePath(opaque));
+    ASSERT_EQ(elem.to_string(store()), opaque);
+}
+
+TEST_F(NixStringContextElemTest, drvDeep) {
+    std::string_view drvDeep = "=/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x.drv";
+    auto elem = NixStringContextElem::parse(store(), drvDeep);
+    auto * p = std::get_if<NixStringContextElem::DrvDeep>(&elem);
+    ASSERT_TRUE(p);
+    ASSERT_EQ(p->drvPath, store().parseStorePath(drvDeep.substr(1)));
+    ASSERT_EQ(elem.to_string(store()), drvDeep);
+}
+
+TEST_F(NixStringContextElemTest, built) {
+    std::string_view built = "!foo!/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x.drv";
+    auto elem = NixStringContextElem::parse(store(), built);
+    auto * p = std::get_if<NixStringContextElem::Built>(&elem);
+    ASSERT_TRUE(p);
+    ASSERT_EQ(p->output, "foo");
+    ASSERT_EQ(p->drvPath, store().parseStorePath(built.substr(5)));
+    ASSERT_EQ(elem.to_string(store()), built);
+}
+
+}

src/libexpr/value-to-json.cc

@@ -1,84 +1,83 @@
 #include "value-to-json.hh"
-#include "json.hh"
 #include "eval-inline.hh"
 #include "util.hh"
+#include "store-api.hh"
 
 #include <cstdlib>
 #include <iomanip>
+#include <nlohmann/json.hpp>
 
 
 namespace nix {
-
-void printValueAsJSON(EvalState & state, bool strict,
-    Value & v, const PosIdx pos, JSONPlaceholder & out, PathSet & context, bool copyToStore)
+using json = nlohmann::json;
+json printValueAsJSON(EvalState & state, bool strict,
+    Value & v, const PosIdx pos, PathSet & context, bool copyToStore)
 {
     checkInterrupt();
 
     if (strict) state.forceValue(v, pos);
 
+    json out;
+
     switch (v.type()) {
 
         case nInt:
-            out.write(v.integer);
+            out = v.integer;
             break;
 
         case nBool:
-            out.write(v.boolean);
+            out = v.boolean;
             break;
 
         case nString:
             copyContext(v, context);
-            out.write(v.string.s);
+            out = v.string.s;
             break;
 
         case nPath:
             if (copyToStore)
-                out.write(state.copyPathToStore(context, v.path));
+                out = state.store->printStorePath(state.copyPathToStore(context, v.path));
             else
-                out.write(v.path);
+                out = v.path;
             break;
 
         case nNull:
-            out.write(nullptr);
             break;
 
         case nAttrs: {
             auto maybeString = state.tryAttrsToString(pos, v, context, false, false);
             if (maybeString) {
-                out.write(*maybeString);
+                out = *maybeString;
                 break;
             }
             auto i = v.attrs->find(state.sOutPath);
             if (i == v.attrs->end()) {
-                auto obj(out.object());
+                out = json::object();
                 StringSet names;
                 for (auto & j : *v.attrs)
                     names.emplace(state.symbols[j.name]);
                 for (auto & j : names) {
                     Attr & a(*v.attrs->find(state.symbols.create(j)));
-                    auto placeholder(obj.placeholder(j));
-                    printValueAsJSON(state, strict, *a.value, a.pos, placeholder, context, copyToStore);
+                    out[j] = printValueAsJSON(state, strict, *a.value, a.pos, context, copyToStore);
                 }
             } else
-                printValueAsJSON(state, strict, *i->value, i->pos, out, context, copyToStore);
+                return printValueAsJSON(state, strict, *i->value, i->pos, context, copyToStore);
             break;
         }
 
         case nList: {
-            auto list(out.list());
-            for (auto elem : v.listItems()) {
-                auto placeholder(list.placeholder());
-                printValueAsJSON(state, strict, *elem, pos, placeholder, context, copyToStore);
-            }
+            out = json::array();
+            for (auto elem : v.listItems())
+                out.push_back(printValueAsJSON(state, strict, *elem, pos, context, copyToStore));
             break;
         }
 
         case nExternal:
-            v.external->printValueAsJSON(state, strict, out, context, copyToStore);
+            return v.external->printValueAsJSON(state, strict, context, copyToStore);
             break;
 
         case nFloat:
-            out.write(v.fpoint);
+            out = v.fpoint;
             break;
 
         case nThunk:
@@ -91,17 +90,17 @@ void printValueAsJSON(EvalState & state, bool strict,
             state.debugThrowLastTrace(e);
             throw e;
     }
+    return out;
 }
 
 void printValueAsJSON(EvalState & state, bool strict,
     Value & v, const PosIdx pos, std::ostream & str, PathSet & context, bool copyToStore)
 {
-    JSONPlaceholder out(str);
-    printValueAsJSON(state, strict, v, pos, out, context, copyToStore);
+    str << printValueAsJSON(state, strict, v, pos, context, copyToStore);
 }
 
-void ExternalValueBase::printValueAsJSON(EvalState & state, bool strict,
-    JSONPlaceholder & out, PathSet & context, bool copyToStore) const
+json ExternalValueBase::printValueAsJSON(EvalState & state, bool strict,
+    PathSet & context, bool copyToStore) const
 {
     state.debugThrowLastTrace(TypeError("cannot convert %1% to JSON", showType()));
 }

src/libexpr/value-to-json.hh

@@ -5,13 +5,12 @@
 
 #include <string>
 #include <map>
+#include <nlohmann/json_fwd.hpp>
 
 namespace nix {
 
-class JSONPlaceholder;
-
-void printValueAsJSON(EvalState & state, bool strict,
-    Value & v, const PosIdx pos, JSONPlaceholder & out, PathSet & context, bool copyToStore = true);
+nlohmann::json printValueAsJSON(EvalState & state, bool strict,
+    Value & v, const PosIdx pos, PathSet & context, bool copyToStore = true);
 
 void printValueAsJSON(EvalState & state, bool strict,
     Value & v, const PosIdx pos, std::ostream & str, PathSet & context, bool copyToStore = true);

src/libexpr/value-to-xml.cc

@@ -24,7 +24,8 @@ static void printValueAsXML(EvalState & state, bool strict, bool location,
 
 static void posToXML(EvalState & state, XMLAttrs & xmlAttrs, const Pos & pos)
 {
-    xmlAttrs["path"] = pos.file;
+    if (auto path = std::get_if<Path>(&pos.origin))
+        xmlAttrs["path"] = *path;
     xmlAttrs["line"] = (format("%1%") % pos.line).str();
     xmlAttrs["column"] = (format("%1%") % pos.column).str();
 }

src/libexpr/value.hh

@@ -3,10 +3,12 @@
 #include <cassert>
 
 #include "symbol-table.hh"
+#include "value/context.hh"
 
 #if HAVE_BOEHMGC
 #include <gc/gc_allocator.h>
 #endif
+#include <nlohmann/json_fwd.hpp>
 
 namespace nix {
 
@@ -62,13 +64,10 @@ class StorePath;
 class Store;
 class EvalState;
 class XMLWriter;
-class JSONPlaceholder;
 
 
 typedef int64_t NixInt;
 typedef double NixFloat;
-typedef std::pair<StorePath, std::string> NixStringContextElem;
-typedef std::vector<NixStringContextElem> NixStringContext;
 
 /* External values must descend from ExternalValueBase, so that
  * type-agnostic nix functions (e.g. showType) can be implemented
@@ -98,8 +97,8 @@ class ExternalValueBase
     virtual bool operator ==(const ExternalValueBase & b) const;
 
     /* Print the value as JSON. Defaults to unconvertable, i.e. throws an error */
-    virtual void printValueAsJSON(EvalState & state, bool strict,
-        JSONPlaceholder & out, PathSet & context, bool copyToStore = true) const;
+    virtual nlohmann::json printValueAsJSON(EvalState & state, bool strict,
+        PathSet & context, bool copyToStore = true) const;
 
     /* Print the value as XML. Defaults to unevaluated */
     virtual void printValueAsXML(EvalState & state, bool strict, bool location,

src/libexpr/value/context.cc

@@ -0,0 +1,67 @@
+#include "value/context.hh"
+#include "store-api.hh"
+
+#include <optional>
+
+namespace nix {
+
+NixStringContextElem NixStringContextElem::parse(const Store & store, std::string_view s0)
+{
+    std::string_view s = s0;
+
+    if (s.size() == 0) {
+        throw BadNixStringContextElem(s0,
+            "String context element should never be an empty string");
+    }
+    switch (s.at(0)) {
+    case '!': {
+        s = s.substr(1); // advance string to parse after first !
+        size_t index = s.find("!");
+        // This makes index + 1 safe. Index can be the length (one after index
+        // of last character), so given any valid character index --- a
+        // successful find --- we can add one.
+        if (index == std::string_view::npos) {
+            throw BadNixStringContextElem(s0,
+                "String content element beginning with '!' should have a second '!'");
+        }
+        return NixStringContextElem::Built {
+            .drvPath = store.parseStorePath(s.substr(index + 1)),
+            .output = std::string(s.substr(0, index)),
+        };
+    }
+    case '=': {
+        return NixStringContextElem::DrvDeep {
+            .drvPath = store.parseStorePath(s.substr(1)),
+        };
+    }
+    default: {
+        return NixStringContextElem::Opaque {
+            .path = store.parseStorePath(s),
+        };
+    }
+    }
+}
+
+std::string NixStringContextElem::to_string(const Store & store) const {
+    return std::visit(overloaded {
+        [&](const NixStringContextElem::Built & b) {
+            std::string res;
+            res += '!';
+            res += b.output;
+            res += '!';
+            res += store.printStorePath(b.drvPath);
+            return res;
+        },
+        [&](const NixStringContextElem::DrvDeep & d) {
+            std::string res;
+            res += '=';
+            res += store.printStorePath(d.drvPath);
+            return res;
+        },
+        [&](const NixStringContextElem::Opaque & o) {
+            return store.printStorePath(o.path);
+        },
+    }, raw());
+}
+
+}

src/libexpr/value/context.hh

@@ -0,0 +1,90 @@
+#pragma once
+
+#include "util.hh"
+#include "path.hh"
+
+#include <optional>
+
+#include <nlohmann/json_fwd.hpp>
+
+namespace nix {
+
+class BadNixStringContextElem : public Error
+{
+public:
+    std::string_view raw;
+
+    template<typename... Args>
+    BadNixStringContextElem(std::string_view raw_, const Args & ... args)
+        : Error("")
+    {
+        raw = raw_;
+        auto hf = hintfmt(args...);
+        err.msg = hintfmt("Bad String Context element: %1%: %2%", normaltxt(hf.str()), raw);
+    }
+};
+
+class Store;
+
+/* Plain opaque path to some store object.
+
+   Encoded as just the path: ‘<path>’.
+*/
+struct NixStringContextElem_Opaque {
+   StorePath path;
+};
+
+/* Path to a derivation and its entire build closure.
+
+   The path doesn't just refer to derivation itself and its closure, but
+   also all outputs of all derivations in that closure (including the
+   root derivation).
+
+   Encoded in the form ‘=<drvPath>’.
+*/
+struct NixStringContextElem_DrvDeep {
+   StorePath drvPath;
+};
+
+/* Derivation output.
+
+   Encoded in the form ‘!<output>!<drvPath>’.
+*/
+struct NixStringContextElem_Built {
+   StorePath drvPath;
+   std::string output;
+};
+
+using _NixStringContextElem_Raw = std::variant<
+    NixStringContextElem_Opaque,
+    NixStringContextElem_DrvDeep,
+    NixStringContextElem_Built
+>;
+
+struct NixStringContextElem : _NixStringContextElem_Raw {
+    using Raw = _NixStringContextElem_Raw;
+    using Raw::Raw;
+
+    using Opaque = NixStringContextElem_Opaque;
+    using DrvDeep = NixStringContextElem_DrvDeep;
+    using Built = NixStringContextElem_Built;
+
+    inline const Raw & raw() const {
+        return static_cast<const Raw &>(*this);
+    }
+    inline Raw & raw() {
+        return static_cast<Raw &>(*this);
+    }
+
+    /* Decode a context string, one of:
+       - ‘<path>’
+       - ‘=<path>’
+       - ‘!<name>!<path>’
+      */
+    static NixStringContextElem parse(const Store & store, std::string_view s);
+    std::string to_string(const Store & store) const;
+};
+
+typedef std::vector<NixStringContextElem> NixStringContext;
+
+}

src/libfetchers/fetch-settings.hh

@@ -71,7 +71,12 @@ struct FetchSettings : public Config
         "Whether to warn about dirty Git/Mercurial trees."};
 
     Setting<std::string> flakeRegistry{this, "https://channels.nixos.org/flake-registry.json", "flake-registry",
-        "Path or URI of the global flake registry."};
+        R"(
+          Path or URI of the global flake registry.
+
+          When empty, disables the global flake registry.
+        )"};
+
 
     Setting<bool> useRegistries{this, true, "use-registries",
         "Whether to use flake registries to resolve flake references."};

src/libfetchers/fetchers.cc

@@ -266,7 +266,7 @@ std::optional<time_t> Input::getLastModified() const
     return {};
 }
 
-ParsedURL InputScheme::toURL(const Input & input)
+ParsedURL InputScheme::toURL(const Input & input) const
 {
     throw Error("don't know how to convert input '%s' to a URL", attrsToJSON(input.attrs));
 }
@@ -274,7 +274,7 @@ ParsedURL InputScheme::toURL(const Input & input)
 Input InputScheme::applyOverrides(
     const Input & input,
     std::optional<std::string> ref,
-    std::optional<Hash> rev)
+    std::optional<Hash> rev) const
 {
     if (ref)
         throw Error("don't know how to set branch/tag name of input '%s' to '%s'", input.to_string(), *ref);
@@ -293,7 +293,7 @@ void InputScheme::markChangedFile(const Input & input, std::string_view file, st
     assert(false);
 }
 
-void InputScheme::clone(const Input & input, const Path & destDir)
+void InputScheme::clone(const Input & input, const Path & destDir) const
 {
     throw Error("do not know how to clone input '%s'", input.to_string());
 }

src/libfetchers/fetchers.hh

@@ -107,26 +107,25 @@ public:
  * recognized.  The Input object contains the information the fetcher
  * needs to actually perform the "fetch()" when called.
  */
-
 struct InputScheme
 {
     virtual ~InputScheme()
     { }
 
-    virtual std::optional<Input> inputFromURL(const ParsedURL & url) = 0;
+    virtual std::optional<Input> inputFromURL(const ParsedURL & url) const = 0;
 
-    virtual std::optional<Input> inputFromAttrs(const Attrs & attrs) = 0;
+    virtual std::optional<Input> inputFromAttrs(const Attrs & attrs) const = 0;
 
-    virtual ParsedURL toURL(const Input & input);
+    virtual ParsedURL toURL(const Input & input) const;
 
-    virtual bool hasAllInfo(const Input & input) = 0;
+    virtual bool hasAllInfo(const Input & input) const = 0;
 
     virtual Input applyOverrides(
         const Input & input,
         std::optional<std::string> ref,
-        std::optional<Hash> rev);
+        std::optional<Hash> rev) const;
 
-    virtual void clone(const Input & input, const Path & destDir);
+    virtual void clone(const Input & input, const Path & destDir) const;
 
     virtual std::optional<Path> getSourcePath(const Input & input);
 

src/libfetchers/git.cc

@@ -18,6 +18,7 @@
 using namespace std::string_literals;
 
 namespace nix::fetchers {
+
 namespace {
 
 // Explicit initial branch of our bare repo to suppress warnings from new version of git.
@@ -26,23 +27,23 @@ namespace {
 // old version of git, which will ignore unrecognized `-c` options.
 const std::string gitInitialBranch = "__nix_dummy_branch";
 
-bool isCacheFileWithinTtl(const time_t now, const struct stat & st)
+bool isCacheFileWithinTtl(time_t now, const struct stat & st)
 {
     return st.st_mtime + settings.tarballTtl > now;
 }
 
-bool touchCacheFile(const Path& path, const time_t& touch_time)
+bool touchCacheFile(const Path & path, time_t touch_time)
 {
-  struct timeval times[2];
-  times[0].tv_sec = touch_time;
-  times[0].tv_usec = 0;
-  times[1].tv_sec = touch_time;
-  times[1].tv_usec = 0;
+    struct timeval times[2];
+    times[0].tv_sec = touch_time;
+    times[0].tv_usec = 0;
+    times[1].tv_sec = touch_time;
+    times[1].tv_usec = 0;
 
-  return lutimes(path.c_str(), times) == 0;
+    return lutimes(path.c_str(), times) == 0;
 }
 
-Path getCachePath(std::string key)
+Path getCachePath(std::string_view key)
 {
     return getCacheDir() + "/nix/gitv3/" +
         hashString(htSHA256, key).to_string(Base32, false);
@@ -57,13 +58,12 @@ Path getCachePath(std::string key)
 //   ...
 std::optional<std::string> readHead(const Path & path)
 {
-    auto [exit_code, output] = runProgram(RunOptions {
+    auto [status, output] = runProgram(RunOptions {
         .program = "git",
+        // FIXME: use 'HEAD' to avoid returning all refs
         .args = {"ls-remote", "--symref", path},
     });
-    if (exit_code != 0) {
-        return std::nullopt;
-    }
+    if (status != 0) return std::nullopt;
 
     std::string_view line = output;
     line = line.substr(0, line.find("\n"));
@@ -82,12 +82,11 @@ std::optional<std::string> readHead(const Path & path)
 }
 
 // Persist the HEAD ref from the remote repo in the local cached repo.
-bool storeCachedHead(const std::string& actualUrl, const std::string& headRef)
+bool storeCachedHead(const std::string & actualUrl, const std::string & headRef)
 {
     Path cacheDir = getCachePath(actualUrl);
-    auto gitDir = ".";
     try {
-        runProgram("git", true, { "-C", cacheDir, "--git-dir", gitDir, "symbolic-ref", "--", "HEAD", headRef });
+        runProgram("git", true, { "-C", cacheDir, "--git-dir", ".", "symbolic-ref", "--", "HEAD", headRef });
     } catch (ExecError &e) {
         if (!WIFEXITED(e.status)) throw;
         return false;
@@ -96,7 +95,7 @@ bool storeCachedHead(const std::string& actualUrl, const std::string& headRef)
     return true;
 }
 
-std::optional<std::string> readHeadCached(const std::string& actualUrl)
+std::optional<std::string> readHeadCached(const std::string & actualUrl)
 {
     // Create a cache path to store the branch of the HEAD ref. Append something
     // in front of the URL to prevent collision with the repository itself.
@@ -110,16 +109,15 @@ std::optional<std::string> readHeadCached(const std::string& actualUrl)
         cachedRef = readHead(cacheDir);
         if (cachedRef != std::nullopt &&
             *cachedRef != gitInitialBranch &&
-            isCacheFileWithinTtl(now, st)) {
+            isCacheFileWithinTtl(now, st))
+        {
             debug("using cached HEAD ref '%s' for repo '%s'", *cachedRef, actualUrl);
             return cachedRef;
         }
     }
 
     auto ref = readHead(actualUrl);
-    if (ref) {
-        return ref;
-    }
+    if (ref) return ref;
 
     if (cachedRef) {
         // If the cached git ref is expired in fetch() below, and the 'git fetch'
@@ -250,7 +248,7 @@ std::pair<StorePath, Input> fetchFromWorkdir(ref<Store> store, Input & input, co
 
 struct GitInputScheme : InputScheme
 {
-    std::optional<Input> inputFromURL(const ParsedURL & url) override
+    std::optional<Input> inputFromURL(const ParsedURL & url) const override
     {
         if (url.scheme != "git" &&
             url.scheme != "git+http" &&
@@ -265,7 +263,7 @@ struct GitInputScheme : InputScheme
         Attrs attrs;
         attrs.emplace("type", "git");
 
-        for (auto &[name, value] : url.query) {
+        for (auto & [name, value] : url.query) {
             if (name == "rev" || name == "ref")
                 attrs.emplace(name, value);
             else if (name == "shallow" || name == "submodules")
@@ -279,7 +277,7 @@ struct GitInputScheme : InputScheme
         return inputFromAttrs(attrs);
     }
 
-    std::optional<Input> inputFromAttrs(const Attrs & attrs) override
+    std::optional<Input> inputFromAttrs(const Attrs & attrs) const override
     {
         if (maybeGetStrAttr(attrs, "type") != "git") return {};
 
@@ -302,7 +300,7 @@ struct GitInputScheme : InputScheme
         return input;
     }
 
-    ParsedURL toURL(const Input & input) override
+    ParsedURL toURL(const Input & input) const override
     {
         auto url = parseURL(getStrAttr(input.attrs, "url"));
         if (url.scheme != "git") url.scheme = "git+" + url.scheme;
@@ -313,7 +311,7 @@ struct GitInputScheme : InputScheme
         return url;
     }
 
-    bool hasAllInfo(const Input & input) override
+    bool hasAllInfo(const Input & input) const override
     {
         bool maybeDirty = !input.getRef();
         bool shallow = maybeGetBoolAttr(input.attrs, "shallow").value_or(false);
@@ -325,7 +323,7 @@ struct GitInputScheme : InputScheme
     Input applyOverrides(
         const Input & input,
         std::optional<std::string> ref,
-        std::optional<Hash> rev) override
+        std::optional<Hash> rev) const override
     {
         auto res(input);
         if (rev) res.attrs.insert_or_assign("rev", rev->gitRev());
@@ -335,7 +333,7 @@ struct GitInputScheme : InputScheme
         return res;
     }
 
-    void clone(const Input & input, const Path & destDir) override
+    void clone(const Input & input, const Path & destDir) const override
     {
         auto [isLocal, actualUrl] = getActualUrl(input);
 
@@ -485,6 +483,10 @@ struct GitInputScheme : InputScheme
                 }
                 input.attrs.insert_or_assign("ref", *head);
                 unlockedAttrs.insert_or_assign("ref", *head);
+            } else {
+                if (!input.getRev()) {
+                    unlockedAttrs.insert_or_assign("ref", input.getRef().value());
+                }
             }
 
             if (auto res = getCache()->lookup(store, unlockedAttrs)) {
@@ -599,9 +601,9 @@ struct GitInputScheme : InputScheme
         {
             throw Error(
                 "Cannot find Git revision '%s' in ref '%s' of repository '%s'! "
-                    "Please make sure that the " ANSI_BOLD "rev" ANSI_NORMAL " exists on the "
-                    ANSI_BOLD "ref" ANSI_NORMAL " you've specified or add " ANSI_BOLD
-                    "allRefs = true;" ANSI_NORMAL " to " ANSI_BOLD "fetchGit" ANSI_NORMAL ".",
+                "Please make sure that the " ANSI_BOLD "rev" ANSI_NORMAL " exists on the "
+                ANSI_BOLD "ref" ANSI_NORMAL " you've specified or add " ANSI_BOLD
+                "allRefs = true;" ANSI_NORMAL " to " ANSI_BOLD "fetchGit" ANSI_NORMAL ".",
                 input.getRev()->gitRev(),
                 *input.getRef(),
                 actualUrl

src/libfetchers/github.cc

@@ -26,11 +26,11 @@ std::regex hostRegex(hostRegexS, std::regex::ECMAScript);
 
 struct GitArchiveInputScheme : InputScheme
 {
-    virtual std::string type() = 0;
+    virtual std::string type() const = 0;
 
     virtual std::optional<std::pair<std::string, std::string>> accessHeaderFromToken(const std::string & token) const = 0;
 
-    std::optional<Input> inputFromURL(const ParsedURL & url) override
+    std::optional<Input> inputFromURL(const ParsedURL & url) const override
     {
         if (url.scheme != type()) return {};
 
@@ -100,7 +100,7 @@ struct GitArchiveInputScheme : InputScheme
         return input;
     }
 
-    std::optional<Input> inputFromAttrs(const Attrs & attrs) override
+    std::optional<Input> inputFromAttrs(const Attrs & attrs) const override
     {
         if (maybeGetStrAttr(attrs, "type") != type()) return {};
 
@@ -116,7 +116,7 @@ struct GitArchiveInputScheme : InputScheme
         return input;
     }
 
-    ParsedURL toURL(const Input & input) override
+    ParsedURL toURL(const Input & input) const override
     {
         auto owner = getStrAttr(input.attrs, "owner");
         auto repo = getStrAttr(input.attrs, "repo");
@@ -132,7 +132,7 @@ struct GitArchiveInputScheme : InputScheme
         };
     }
 
-    bool hasAllInfo(const Input & input) override
+    bool hasAllInfo(const Input & input) const override
     {
         return input.getRev() && maybeGetIntAttr(input.attrs, "lastModified");
     }
@@ -140,7 +140,7 @@ struct GitArchiveInputScheme : InputScheme
     Input applyOverrides(
         const Input & _input,
         std::optional<std::string> ref,
-        std::optional<Hash> rev) override
+        std::optional<Hash> rev) const override
     {
         auto input(_input);
         if (rev && ref)
@@ -227,7 +227,7 @@ struct GitArchiveInputScheme : InputScheme
 
 struct GitHubInputScheme : GitArchiveInputScheme
 {
-    std::string type() override { return "github"; }
+    std::string type() const override { return "github"; }
 
     std::optional<std::pair<std::string, std::string>> accessHeaderFromToken(const std::string & token) const override
     {
@@ -240,14 +240,29 @@ struct GitHubInputScheme : GitArchiveInputScheme
         return std::pair<std::string, std::string>("Authorization", fmt("token %s", token));
     }
 
+    std::string getHost(const Input & input) const
+    {
+        return maybeGetStrAttr(input.attrs, "host").value_or("github.com");
+    }
+
+    std::string getOwner(const Input & input) const
+    {
+        return getStrAttr(input.attrs, "owner");
+    }
+
+    std::string getRepo(const Input & input) const
+    {
+        return getStrAttr(input.attrs, "repo");
+    }
+
     Hash getRevFromRef(nix::ref<Store> store, const Input & input) const override
     {
-        auto host = maybeGetStrAttr(input.attrs, "host").value_or("github.com");
+        auto host = getHost(input);
         auto url = fmt(
             host == "github.com"
             ? "https://api.%s/repos/%s/%s/commits/%s"
             : "https://%s/api/v3/repos/%s/%s/commits/%s",
-            host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo"), *input.getRef());
+            host, getOwner(input), getRepo(input), *input.getRef());
 
         Headers headers = makeHeadersWithAuthTokens(host);
 
@@ -262,25 +277,30 @@ struct GitHubInputScheme : GitArchiveInputScheme
 
     DownloadUrl getDownloadUrl(const Input & input) const override
     {
-        // FIXME: use regular /archive URLs instead? api.github.com
-        // might have stricter rate limits.
-        auto host = maybeGetStrAttr(input.attrs, "host").value_or("github.com");
-        auto url = fmt(
-            host == "github.com"
-            ? "https://api.%s/repos/%s/%s/tarball/%s"
-            : "https://%s/api/v3/repos/%s/%s/tarball/%s",
-            host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo"),
-            input.getRev()->to_string(Base16, false));
+        auto host = getHost(input);
 
         Headers headers = makeHeadersWithAuthTokens(host);
+
+        // If we have no auth headers then we default to the public archive
+        // urls so we do not run into rate limits.
+        const auto urlFmt =
+            host != "github.com"
+            ? "https://%s/api/v3/repos/%s/%s/tarball/%s"
+            : headers.empty()
+            ? "https://%s/%s/%s/archive/%s.tar.gz"
+            : "https://api.%s/repos/%s/%s/tarball/%s";
+
+        const auto url = fmt(urlFmt, host, getOwner(input), getRepo(input),
+            input.getRev()->to_string(Base16, false));
+
         return DownloadUrl { url, headers };
     }
 
-    void clone(const Input & input, const Path & destDir) override
+    void clone(const Input & input, const Path & destDir) const override
     {
-        auto host = maybeGetStrAttr(input.attrs, "host").value_or("github.com");
+        auto host = getHost(input);
         Input::fromURL(fmt("git+https://%s/%s/%s.git",
-                host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo")))
+                host, getOwner(input), getRepo(input)))
             .applyOverrides(input.getRef(), input.getRev())
             .clone(destDir);
     }
@@ -288,7 +308,7 @@ struct GitHubInputScheme : GitArchiveInputScheme
 
 struct GitLabInputScheme : GitArchiveInputScheme
 {
-    std::string type() override { return "gitlab"; }
+    std::string type() const override { return "gitlab"; }
 
     std::optional<std::pair<std::string, std::string>> accessHeaderFromToken(const std::string & token) const override
     {
@@ -343,7 +363,7 @@ struct GitLabInputScheme : GitArchiveInputScheme
         return DownloadUrl { url, headers };
     }
 
-    void clone(const Input & input, const Path & destDir) override
+    void clone(const Input & input, const Path & destDir) const override
     {
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("gitlab.com");
         // FIXME: get username somewhere
@@ -356,7 +376,7 @@ struct GitLabInputScheme : GitArchiveInputScheme
 
 struct SourceHutInputScheme : GitArchiveInputScheme
 {
-    std::string type() override { return "sourcehut"; }
+    std::string type() const override { return "sourcehut"; }
 
     std::optional<std::pair<std::string, std::string>> accessHeaderFromToken(const std::string & token) const override
     {
@@ -430,7 +450,7 @@ struct SourceHutInputScheme : GitArchiveInputScheme
         return DownloadUrl { url, headers };
     }
 
-    void clone(const Input & input, const Path & destDir) override
+    void clone(const Input & input, const Path & destDir) const override
     {
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("git.sr.ht");
         Input::fromURL(fmt("git+https://%s/%s/%s",

src/libfetchers/indirect.cc

@@ -7,7 +7,7 @@ std::regex flakeRegex("[a-zA-Z][a-zA-Z0-9_-]*", std::regex::ECMAScript);
 
 struct IndirectInputScheme : InputScheme
 {
-    std::optional<Input> inputFromURL(const ParsedURL & url) override
+    std::optional<Input> inputFromURL(const ParsedURL & url) const override
     {
         if (url.scheme != "flake") return {};
 
@@ -50,7 +50,7 @@ struct IndirectInputScheme : InputScheme
         return input;
     }
 
-    std::optional<Input> inputFromAttrs(const Attrs & attrs) override
+    std::optional<Input> inputFromAttrs(const Attrs & attrs) const override
     {
         if (maybeGetStrAttr(attrs, "type") != "indirect") return {};
 
@@ -68,7 +68,7 @@ struct IndirectInputScheme : InputScheme
         return input;
     }
 
-    ParsedURL toURL(const Input & input) override
+    ParsedURL toURL(const Input & input) const override
     {
         ParsedURL url;
         url.scheme = "flake";
@@ -78,7 +78,7 @@ struct IndirectInputScheme : InputScheme
         return url;
     }
 
-    bool hasAllInfo(const Input & input) override
+    bool hasAllInfo(const Input & input) const override
     {
         return false;
     }
@@ -86,7 +86,7 @@ struct IndirectInputScheme : InputScheme
     Input applyOverrides(
         const Input & _input,
         std::optional<std::string> ref,
-        std::optional<Hash> rev) override
+        std::optional<Hash> rev) const override
     {
         auto input(_input);
         if (rev) input.attrs.insert_or_assign("rev", rev->gitRev());

src/libfetchers/mercurial.cc

@@ -43,7 +43,7 @@ static std::string runHg(const Strings & args, const std::optional<std::string>
 
 struct MercurialInputScheme : InputScheme
 {
-    std::optional<Input> inputFromURL(const ParsedURL & url) override
+    std::optional<Input> inputFromURL(const ParsedURL & url) const override
     {
         if (url.scheme != "hg+http" &&
             url.scheme != "hg+https" &&
@@ -69,7 +69,7 @@ struct MercurialInputScheme : InputScheme
         return inputFromAttrs(attrs);
     }
 
-    std::optional<Input> inputFromAttrs(const Attrs & attrs) override
+    std::optional<Input> inputFromAttrs(const Attrs & attrs) const override
     {
         if (maybeGetStrAttr(attrs, "type") != "hg") return {};
 
@@ -89,7 +89,7 @@ struct MercurialInputScheme : InputScheme
         return input;
     }
 
-    ParsedURL toURL(const Input & input) override
+    ParsedURL toURL(const Input & input) const override
     {
         auto url = parseURL(getStrAttr(input.attrs, "url"));
         url.scheme = "hg+" + url.scheme;
@@ -98,7 +98,7 @@ struct MercurialInputScheme : InputScheme
         return url;
     }
 
-    bool hasAllInfo(const Input & input) override
+    bool hasAllInfo(const Input & input) const override
     {
         // FIXME: ugly, need to distinguish between dirty and clean
         // default trees.
@@ -108,7 +108,7 @@ struct MercurialInputScheme : InputScheme
     Input applyOverrides(
         const Input & input,
         std::optional<std::string> ref,
-        std::optional<Hash> rev) override
+        std::optional<Hash> rev) const override
     {
         auto res(input);
         if (rev) res.attrs.insert_or_assign("rev", rev->gitRev());