Move StringData to its own header

Now that it isn't just used for `Value`, it doesn't really belong in
there.

Rename `static-string-data.hh` to share the same prefix to keep them
close together when sorting lines, also.

.github/workflows/ci.yml

@@ -174,7 +174,7 @@ jobs:
         echo "installer-url=file://$GITHUB_WORKSPACE/out" >> "$GITHUB_OUTPUT"
         TARBALL_PATH="$(find "$GITHUB_WORKSPACE/out" -name 'nix*.tar.xz' -print | head -n 1)"
         echo "tarball-path=file://$TARBALL_PATH" >> "$GITHUB_OUTPUT"
-    - uses: cachix/install-nix-action@456688f15bc354bef6d396e4a35f4f89d40bf2b7 # v31.8.2
+    - uses: cachix/install-nix-action@7ec16f2c061ab07b235a7245e06ed46fe9a1cab6 # v31.8.3
       if: ${{ !matrix.experimental-installer }}
       with:
         install_url: ${{ format('{0}/install', steps.installer-tarball-url.outputs.installer-url) }}

src/libcmd/common-eval-args.cc

@@ -33,7 +33,8 @@ EvalSettings evalSettings{
                 // FIXME `parseFlakeRef` should take a `std::string_view`.
                 auto flakeRef = parseFlakeRef(fetchSettings, std::string{rest}, {}, true, false);
                 debug("fetching flake search path element '%s''", rest);
-                auto [accessor, lockedRef] = flakeRef.resolve(state.store).lazyFetch(state.store);
+                auto [accessor, lockedRef] =
+                    flakeRef.resolve(fetchSettings, state.store).lazyFetch(fetchSettings, state.store);
                 auto storePath = nix::fetchToStore(
                     state.fetchSettings,
                     *state.store,
@@ -131,7 +132,7 @@ MixEvalArgs::MixEvalArgs()
             fetchers::Attrs extraAttrs;
             if (to.subdir != "")
                 extraAttrs["dir"] = to.subdir;
-            fetchers::overrideRegistry(from.input, to.input, extraAttrs);
+            fetchers::overrideRegistry(fetchSettings, from.input, to.input, extraAttrs);
         }},
         .completer = {[&](AddCompletions & completions, size_t, std::string_view prefix) {
             completeFlakeRef(completions, openStore(), prefix);
@@ -187,7 +188,7 @@ SourcePath lookupFileArg(EvalState & state, std::string_view s, const Path * bas
     else if (hasPrefix(s, "flake:")) {
         experimentalFeatureSettings.require(Xp::Flakes);
         auto flakeRef = parseFlakeRef(fetchSettings, std::string(s.substr(6)), {}, true, false);
-        auto [accessor, lockedRef] = flakeRef.resolve(state.store).lazyFetch(state.store);
+        auto [accessor, lockedRef] = flakeRef.resolve(fetchSettings, state.store).lazyFetch(fetchSettings, state.store);
         auto storePath = nix::fetchToStore(
             state.fetchSettings, *state.store, SourcePath(accessor), FetchMode::Copy, lockedRef.input.getName());
         state.allowPath(storePath);

src/libcmd/installables.cc

@@ -185,6 +185,7 @@ MixFlakeOptions::MixFlakeOptions()
                     }
 
                     overrideRegistry(
+                        fetchSettings,
                         fetchers::Input::fromAttrs(fetchSettings, {{"type", "indirect"}, {"id", inputName}}),
                         input3->lockedRef.input,
                         extraAttrs);

src/libcmd/repl.cc

@@ -656,7 +656,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
                             + "\n\n";
             }
 
-            markdown += stripIndentation(doc->doc);
+            markdown += stripIndentation(doc->doc.view());
 
             logger->cout(trim(renderMarkdownToTerminal(markdown)));
         } else if (fallbackPos) {
@@ -738,7 +738,7 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
     }
 
     auto flakeRef = parseFlakeRef(fetchSettings, flakeRefS, cwd.string(), true);
-    if (evalSettings.pureEval && !flakeRef.input.isLocked())
+    if (evalSettings.pureEval && !flakeRef.input.isLocked(fetchSettings))
         throw Error("cannot use ':load-flake' on locked flake reference '%s' (use --impure to override)", flakeRefS);
 
     Value v;

src/libexpr-c/nix_api_expr.cc

@@ -137,6 +137,8 @@ nix_eval_state_builder * nix_eval_state_builder_new(nix_c_context * context, Sto
 
 void nix_eval_state_builder_free(nix_eval_state_builder * builder)
 {
+    if (builder)
+        builder->~nix_eval_state_builder();
     operator delete(builder, static_cast<std::align_val_t>(alignof(nix_eval_state_builder)));
 }
 
@@ -203,6 +205,8 @@ EvalState * nix_state_create(nix_c_context * context, const char ** lookupPath_c
 
 void nix_state_free(EvalState * state)
 {
+    if (state)
+        state->~EvalState();
     operator delete(state, static_cast<std::align_val_t>(alignof(EvalState)));
 }
 

src/libexpr-c/nix_api_value.cc

@@ -134,7 +134,7 @@ PrimOp * nix_alloc_primop(
                     .name = name,
                     .args = {},
                     .arity = (size_t) arity,
-                    .doc = doc,
+                    .doc = &nix::StringData::make(doc),
                     .fun = std::bind(nix_c_primop_wrapper, fun, user_data, _1, _2, _3, _4)};
         if (args)
             for (size_t i = 0; args[i]; i++)

src/libexpr-tests/json.cc

@@ -1,6 +1,6 @@
 #include "nix/expr/tests/libexpr.hh"
 #include "nix/expr/value-to-json.hh"
-#include "nix/expr/static-string-data.hh"
+#include "nix/expr/string-data-static.hh"
 
 namespace nix {
 // Testing the conversion to JSON

src/libexpr-tests/nix_api_expr.cc

@@ -14,7 +14,7 @@
 
 namespace nixC {
 
-TEST_F(nix_api_store_test, nix_eval_state_lookup_path)
+TEST_F(nix_api_expr_test, nix_eval_state_lookup_path)
 {
     auto tmpDir = nix::createTempDir();
     auto delTmpDir = std::make_unique<nix::AutoDelete>(tmpDir, true);
@@ -42,12 +42,16 @@ TEST_F(nix_api_store_test, nix_eval_state_lookup_path)
     nix_expr_eval_from_string(ctx, state, "builtins.seq <nixos-config> <nixpkgs>", ".", value);
     assert_ctx_ok();
 
+    nix_state_free(state);
+
     ASSERT_EQ(nix_get_type(ctx, value), NIX_TYPE_PATH);
     assert_ctx_ok();
 
     auto pathStr = nix_get_path_string(ctx, value);
     assert_ctx_ok();
     ASSERT_EQ(0, strcmp(pathStr, nixpkgs.c_str()));
+
+    nix_gc_decref(nullptr, value);
 }
 
 TEST_F(nix_api_expr_test, nix_expr_eval_from_string)

src/libexpr-tests/primops.cc

@@ -661,8 +661,14 @@ INSTANTIATE_TEST_SUITE_P(
         CASE(R"(null)", ""),
         CASE(R"({ v = "bar"; __toString = self: self.v; })", "bar"),
         CASE(R"({ v = "bar"; __toString = self: self.v; outPath = "foo"; })", "bar"),
-        CASE(R"({ outPath = "foo"; })", "foo"),
-        CASE(R"(./test)", "/test")));
+        CASE(R"({ outPath = "foo"; })", "foo")
+// this is broken on cygwin because canonPath("//./test", false) returns //./test
+// FIXME: don't use canonPath
+#ifndef __CYGWIN__
+            ,
+        CASE(R"(./test)", "/test")
+#endif
+            ));
 #undef CASE
 
 TEST_F(PrimOpTest, substring)

src/libexpr-tests/value/print.cc

@@ -1,5 +1,5 @@
 #include "nix/expr/tests/libexpr.hh"
-#include "nix/expr/static-string-data.hh"
+#include "nix/expr/string-data-static.hh"
 
 #include "nix/expr/value.hh"
 #include "nix/expr/print.hh"

src/libexpr-tests/value/value.cc

@@ -1,5 +1,5 @@
 #include "nix/expr/value.hh"
-#include "nix/expr/static-string-data.hh"
+#include "nix/expr/string-data-static.hh"
 
 #include "nix/store/tests/libstore.hh"
 #include <gtest/gtest.h>

src/libexpr/eval.cc

@@ -51,36 +51,6 @@ using json = nlohmann::json;
 
 namespace nix {
 
-/**
- * Just for doc strings. Not for regular string values.
- */
-static char * allocString(size_t size)
-{
-    char * t;
-    t = (char *) GC_MALLOC_ATOMIC(size);
-    if (!t)
-        throw std::bad_alloc();
-    return t;
-}
-
-// When there's no need to write to the string, we can optimize away empty
-// string allocations.
-// This function handles makeImmutableString(std::string_view()) by returning
-// the empty string.
-/**
- * Just for doc strings. Not for regular string values.
- */
-static const char * makeImmutableString(std::string_view s)
-{
-    const size_t size = s.size();
-    if (size == 0)
-        return "";
-    auto t = allocString(size + 1);
-    memcpy(t, s.data(), size);
-    t[size] = '\0';
-    return t;
-}
-
 StringData & StringData::alloc(size_t size)
 {
     void * t = GC_MALLOC_ATOMIC(sizeof(StringData) + size + 1);
@@ -571,7 +541,7 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
                 .name = v2->primOp()->name,
                 .arity = v2->primOp()->arity,
                 .args = v2->primOp()->args,
-                .doc = doc,
+                .doc = *doc,
             };
     }
     if (v.isLambda()) {
@@ -613,9 +583,8 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
             .name = name,
             .arity = 0, // FIXME: figure out how deep by syntax only? It's not semantically useful though...
             .args = {},
-            /* N.B. Can't use StringData here, because that would lead to an interior pointer.
-               NOTE: memory leak when compiled without GC. */
-            .doc = makeImmutableString(s.view()),
+            /* NOTE: memory leak when compiled without GC. */
+            .doc = StringData::make(s.view()),
         };
     }
     if (isFunctor(v)) {

src/libexpr/include/nix/expr/eval.hh

@@ -108,7 +108,7 @@ struct PrimOp
     /**
      * Optional free-form documentation about the primop.
      */
-    const char * doc = nullptr;
+    const StringData * doc = nullptr;
 
     /**
      * Add a trace item, while calling the `<name>` builtin.
@@ -156,7 +156,7 @@ struct Constant
     /**
      * Optional free-form documentation about the constant.
      */
-    const char * doc = nullptr;
+    const StringData * doc = nullptr;
 
     /**
      * Whether the constant is impure, and not available in pure mode.
@@ -837,11 +837,7 @@ public:
         std::optional<std::string> name;
         size_t arity;
         std::vector<std::string> args;
-        /**
-         * Unlike the other `doc` fields in this file, this one should never be
-         * `null`.
-         */
-        const char * doc;
+        const StringData & doc;
     };
 
     /**

src/libexpr/include/nix/expr/meson.build

@@ -31,7 +31,8 @@ headers = [ config_pub_h ] + files(
   'print.hh',
   'repl-exit-status.hh',
   'search-path.hh',
-  'static-string-data.hh',
+  'string-data.hh',
+  'string-data-static.hh',
   'symbol-table.hh',
   'value-to-json.hh',
   'value-to-xml.hh',

src/libexpr/include/nix/expr/nixexpr.hh

@@ -12,7 +12,7 @@
 #include "nix/expr/value.hh"
 #include "nix/expr/symbol-table.hh"
 #include "nix/expr/eval-error.hh"
-#include "nix/expr/static-string-data.hh"
+#include "nix/expr/string-data-static.hh"
 #include "nix/util/pos-idx.hh"
 #include "nix/expr/counter.hh"
 #include "nix/util/pos-table.hh"

src/libexpr/include/nix/expr/parser-state.hh

@@ -5,7 +5,7 @@
 
 #include "nix/expr/eval.hh"
 #include "nix/expr/value.hh"
-#include "nix/expr/static-string-data.hh"
+#include "nix/expr/string-data-static.hh"
 
 namespace nix {
 

src/libexpr/include/nix/expr/string-data-static.hh

@@ -1,7 +1,7 @@
 #pragma once
 ///@file
 
-#include "nix/expr/value.hh"
+#include "nix/expr/string-data.hh"
 
 namespace nix {
 

src/libexpr/include/nix/expr/string-data.hh

@@ -0,0 +1,96 @@
+#pragma once
+///@file
+
+#include <cstddef>
+#include <cstring>
+#include <memory_resource>
+#include <string_view>
+
+namespace nix {
+
+class StringData
+{
+public:
+    using size_type = std::size_t;
+
+    size_type size_;
+    char data_[];
+
+    /*
+     * This in particular ensures that we cannot have a `StringData`
+     * that we use by value, which is just what we want!
+     *
+     * Dynamically sized types aren't a thing in C++ and even flexible array
+     * members are a language extension and beyond the realm of standard C++.
+     * Technically, sizeof data_ member is 0 and the intended way to use flexible
+     * array members is to allocate sizeof(StrindData) + count * sizeof(char) bytes
+     * and the compiler will consider alignment restrictions for the FAM.
+     *
+     */
+
+    StringData(StringData &&) = delete;
+    StringData & operator=(StringData &&) = delete;
+    StringData(const StringData &) = delete;
+    StringData & operator=(const StringData &) = delete;
+    ~StringData() = default;
+
+private:
+    StringData() = delete;
+
+    explicit StringData(size_type size)
+        : size_(size)
+    {
+    }
+
+public:
+    /**
+     * Allocate StringData on the (possibly) GC-managed heap and copy
+     * the contents of s to it.
+     */
+    static const StringData & make(std::string_view s);
+
+    /**
+     * Allocate StringData on the (possibly) GC-managed heap.
+     * @param size Length of the string (without the NUL terminator).
+     */
+    static StringData & alloc(size_t size);
+
+    size_t size() const
+    {
+        return size_;
+    }
+
+    char * data() noexcept
+    {
+        return data_;
+    }
+
+    const char * data() const noexcept
+    {
+        return data_;
+    }
+
+    const char * c_str() const noexcept
+    {
+        return data_;
+    }
+
+    constexpr std::string_view view() const noexcept
+    {
+        return std::string_view(data_, size_);
+    }
+
+    template<size_t N>
+    struct Static;
+
+    static StringData & make(std::pmr::memory_resource & resource, std::string_view s)
+    {
+        auto & res =
+            *new (resource.allocate(sizeof(StringData) + s.size() + 1, alignof(StringData))) StringData(s.size());
+        std::memcpy(res.data_, s.data(), s.size());
+        res.data_[s.size()] = '\0';
+        return res;
+    }
+};
+
+} // namespace nix

src/libexpr/include/nix/expr/symbol-table.hh

@@ -3,7 +3,7 @@
 
 #include <memory_resource>
 #include "nix/expr/value.hh"
-#include "nix/expr/static-string-data.hh"
+#include "nix/expr/string-data-static.hh"
 #include "nix/util/chunked-vector.hh"
 #include "nix/util/error.hh"
 

src/libexpr/include/nix/expr/value.hh

@@ -3,16 +3,14 @@
 
 #include <bit>
 #include <cassert>
-#include <cstddef>
-#include <cstring>
 #include <memory>
-#include <memory_resource>
 #include <span>
 #include <string_view>
 #include <type_traits>
 #include <concepts>
 
 #include "nix/expr/eval-gc.hh"
+#include "nix/expr/string-data.hh"
 #include "nix/expr/value/context.hh"
 #include "nix/util/source-path.hh"
 #include "nix/expr/print-options.hh"
@@ -193,91 +191,6 @@ public:
     friend struct Value;
 };
 
-class StringData
-{
-public:
-    using size_type = std::size_t;
-
-    size_type size_;
-    char data_[];
-
-    /*
-     * This in particular ensures that we cannot have a `StringData`
-     * that we use by value, which is just what we want!
-     *
-     * Dynamically sized types aren't a thing in C++ and even flexible array
-     * members are a language extension and beyond the realm of standard C++.
-     * Technically, sizeof data_ member is 0 and the intended way to use flexible
-     * array members is to allocate sizeof(StrindData) + count * sizeof(char) bytes
-     * and the compiler will consider alignment restrictions for the FAM.
-     *
-     */
-
-    StringData(StringData &&) = delete;
-    StringData & operator=(StringData &&) = delete;
-    StringData(const StringData &) = delete;
-    StringData & operator=(const StringData &) = delete;
-    ~StringData() = default;
-
-private:
-    StringData() = delete;
-
-    explicit StringData(size_type size)
-        : size_(size)
-    {
-    }
-
-public:
-    /**
-     * Allocate StringData on the (possibly) GC-managed heap and copy
-     * the contents of s to it.
-     */
-    static const StringData & make(std::string_view s);
-
-    /**
-     * Allocate StringData on the (possibly) GC-managed heap.
-     * @param size Length of the string (without the NUL terminator).
-     */
-    static StringData & alloc(size_t size);
-
-    size_t size() const
-    {
-        return size_;
-    }
-
-    char * data() noexcept
-    {
-        return data_;
-    }
-
-    const char * data() const noexcept
-    {
-        return data_;
-    }
-
-    const char * c_str() const noexcept
-    {
-        return data_;
-    }
-
-    constexpr std::string_view view() const noexcept
-    {
-        return std::string_view(data_, size_);
-    }
-
-    template<size_t N>
-    struct Static;
-
-    static StringData & make(std::pmr::memory_resource & resource, std::string_view s)
-    {
-        auto & res =
-            *new (resource.allocate(sizeof(StringData) + s.size() + 1, alignof(StringData))) StringData(s.size());
-        std::memcpy(res.data_, s.data(), s.size());
-        res.data_[s.size()] = '\0';
-        return res;
-    }
-};
-
 namespace detail {
 
 /**

src/libexpr/primops/context.cc

@@ -1,5 +1,6 @@
 #include "nix/expr/primops.hh"
 #include "nix/expr/eval-inline.hh"
+#include "nix/expr/string-data-static.hh"
 #include "nix/store/derivations.hh"
 #include "nix/store/store-api.hh"
 #include "nix/store/globals.hh"
@@ -17,9 +18,9 @@ static void prim_unsafeDiscardStringContext(EvalState & state, const PosIdx pos,
 static RegisterPrimOp primop_unsafeDiscardStringContext({
     .name = "__unsafeDiscardStringContext",
     .args = {"s"},
-    .doc = R"(
+    .doc = &R"(
         Discard the [string context](@docroot@/language/string-context.md) from a value that can be coerced to a string.
-    )",
+    )"_sds,
     .fun = prim_unsafeDiscardStringContext,
 });
 
@@ -33,7 +34,7 @@ static void prim_hasContext(EvalState & state, const PosIdx pos, Value ** args,
 static RegisterPrimOp primop_hasContext(
     {.name = "__hasContext",
      .args = {"s"},
-     .doc = R"(
+     .doc = &R"(
       Return `true` if string *s* has a non-empty context.
       The context can be obtained with
       [`getContext`](#builtins-getContext).
@@ -50,7 +51,7 @@ static RegisterPrimOp primop_hasContext(
       > then throw "package name cannot contain string context"
       > else { ${name} = meta; }
       > ```
-    )",
+    )"_sds,
      .fun = prim_hasContext});
 
 static void prim_unsafeDiscardOutputDependency(EvalState & state, const PosIdx pos, Value ** args, Value & v)
@@ -75,7 +76,7 @@ static void prim_unsafeDiscardOutputDependency(EvalState & state, const PosIdx p
 static RegisterPrimOp primop_unsafeDiscardOutputDependency(
     {.name = "__unsafeDiscardOutputDependency",
      .args = {"s"},
-     .doc = R"(
+     .doc = &R"(
       Create a copy of the given string where every
       [derivation deep](@docroot@/language/string-context.md#string-context-element-derivation-deep)
       string context element is turned into a
@@ -91,7 +92,7 @@ static RegisterPrimOp primop_unsafeDiscardOutputDependency(
       Replacing a constant string context element with a "derivation deep" element is a safe operation that just enlargens the string context without forgetting anything.
 
       [`builtins.addDrvOutputDependencies`]: #builtins-addDrvOutputDependencies
-    )",
+    )"_sds,
      .fun = prim_unsafeDiscardOutputDependency});
 
 static void prim_addDrvOutputDependencies(EvalState & state, const PosIdx pos, Value ** args, Value & v)
@@ -143,7 +144,7 @@ static void prim_addDrvOutputDependencies(EvalState & state, const PosIdx pos, V
 static RegisterPrimOp primop_addDrvOutputDependencies(
     {.name = "__addDrvOutputDependencies",
      .args = {"s"},
-     .doc = R"(
+     .doc = &R"(
       Create a copy of the given string where a single
       [constant](@docroot@/language/string-context.md#string-context-constant)
       string context element is turned into a
@@ -156,7 +157,7 @@ static RegisterPrimOp primop_addDrvOutputDependencies(
       The latter is supported so this function is idempotent.
 
       This is the opposite of [`builtins.unsafeDiscardOutputDependency`](#builtins-unsafeDiscardOutputDependency).
-    )",
+    )"_sds,
      .fun = prim_addDrvOutputDependencies});
 
 /* Extract the context of a string as a structured Nix value.
@@ -230,7 +231,7 @@ static void prim_getContext(EvalState & state, const PosIdx pos, Value ** args,
 static RegisterPrimOp primop_getContext(
     {.name = "__getContext",
      .args = {"s"},
-     .doc = R"(
+     .doc = &R"(
       Return the string context of *s*.
 
       The string context tracks references to derivations within a string.
@@ -248,7 +249,7 @@ static RegisterPrimOp primop_getContext(
       ```
       { "/nix/store/arhvjaf6zmlyn8vh8fgn55rpwnxq0n7l-a.drv" = { outputs = [ "out" ]; }; }
       ```
-    )",
+    )"_sds,
      .fun = prim_getContext});
 
 /* Append the given context to a given string.

src/libexpr/primops/fetchClosure.cc

@@ -1,4 +1,5 @@
 #include "nix/expr/primops.hh"
+#include "nix/expr/string-data-static.hh"
 #include "nix/store/store-open.hh"
 #include "nix/store/realisation.hh"
 #include "nix/store/make-content-addressed.hh"
@@ -216,7 +217,7 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value ** args
 static RegisterPrimOp primop_fetchClosure({
     .name = "__fetchClosure",
     .args = {"args"},
-    .doc = R"(
+    .doc = &R"(
       Fetch a store path [closure](@docroot@/glossary.md#gloss-closure) from a binary cache, and return the store path as a string with context.
 
       This function can be invoked in three ways that we will discuss in order of preference.
@@ -284,7 +285,7 @@ static RegisterPrimOp primop_fetchClosure({
       `fetchClosure` is similar to [`builtins.storePath`](#builtins-storePath) in that it allows you to use a previously built store path in a Nix expression.
       However, `fetchClosure` is more reproducible because it specifies a binary cache from which the path can be fetched.
       Also, using content-addressed store paths does not require users to configure [`trusted-public-keys`](@docroot@/command-ref/conf-file.md#conf-trusted-public-keys) to ensure their authenticity.
-    )",
+    )"_sds,
     .fun = prim_fetchClosure,
     .experimentalFeature = Xp::FetchClosure,
 });

src/libexpr/primops/fetchMercurial.cc

@@ -81,7 +81,7 @@ static void prim_fetchMercurial(EvalState & state, const PosIdx pos, Value ** ar
         attrs.insert_or_assign("rev", rev->gitRev());
     auto input = fetchers::Input::fromAttrs(state.fetchSettings, std::move(attrs));
 
-    auto [storePath, input2] = input.fetchToStore(state.store);
+    auto [storePath, input2] = input.fetchToStore(state.fetchSettings, state.store);
 
     auto attrs2 = state.buildBindings(8);
     state.mkStorePathString(storePath, attrs2.alloc(state.s.outPath));

src/libexpr/primops/fetchTree.cc

@@ -2,6 +2,7 @@
 #include "nix/expr/primops.hh"
 #include "nix/expr/eval-inline.hh"
 #include "nix/expr/eval-settings.hh"
+#include "nix/expr/string-data-static.hh"
 #include "nix/store/store-api.hh"
 #include "nix/fetchers/fetchers.hh"
 #include "nix/store/filetransfer.hh"
@@ -82,7 +83,7 @@ struct FetchTreeParams
 static void fetchTree(
     EvalState & state, const PosIdx pos, Value ** args, Value & v, const FetchTreeParams & params = FetchTreeParams{})
 {
-    fetchers::Input input{state.fetchSettings};
+    fetchers::Input input{};
     NixStringContext context;
     std::optional<std::string> type;
     auto fetcher = params.isFetchGit ? "fetchGit" : "fetchTree";
@@ -194,9 +195,9 @@ static void fetchTree(
     }
 
     if (!state.settings.pureEval && !input.isDirect() && experimentalFeatureSettings.isEnabled(Xp::Flakes))
-        input = lookupInRegistries(state.store, input, fetchers::UseRegistries::Limited).first;
+        input = lookupInRegistries(state.fetchSettings, state.store, input, fetchers::UseRegistries::Limited).first;
 
-    if (state.settings.pureEval && !input.isLocked()) {
+    if (state.settings.pureEval && !input.isLocked(state.fetchSettings)) {
         if (input.getNarHash())
             warn(
                 "Input '%s' is unlocked (e.g. lacks a Git revision) but is checked by NAR hash. "
@@ -219,7 +220,8 @@ static void fetchTree(
             throw Error("input '%s' is not allowed to use the '__final' attribute", input.to_string());
     }
 
-    auto cachedInput = state.inputCache->getAccessor(state.store, input, fetchers::UseRegistries::No);
+    auto cachedInput =
+        state.inputCache->getAccessor(state.fetchSettings, state.store, input, fetchers::UseRegistries::No);
 
     auto storePath = state.mountInput(cachedInput.lockedInput, input, cachedInput.accessor);
 
@@ -234,7 +236,7 @@ static void prim_fetchTree(EvalState & state, const PosIdx pos, Value ** args, V
 static RegisterPrimOp primop_fetchTree({
     .name = "fetchTree",
     .args = {"input"},
-    .doc = R"(
+    .doc = &R"(
       Fetch a file system tree or a plain file using one of the supported backends and return an attribute set with:
 
       - the resulting fixed-output [store path](@docroot@/store/store-path.md)
@@ -456,7 +458,7 @@ static RegisterPrimOp primop_fetchTree({
       >   ```nix
       >   builtins.fetchTree "github:NixOS/nixpkgs/ae2e6b3958682513d28f7d633734571fb18285dd"
       >   ```
-    )",
+    )"_sds,
     .fun = prim_fetchTree,
     .experimentalFeature = Xp::FetchTree,
 });
@@ -616,7 +618,7 @@ static void prim_fetchurl(EvalState & state, const PosIdx pos, Value ** args, Va
 static RegisterPrimOp primop_fetchurl({
     .name = "__fetchurl",
     .args = {"arg"},
-    .doc = R"(
+    .doc = &R"(
       Download the specified URL and return the path of the downloaded file.
       `arg` can be either a string denoting the URL, or an attribute set with the following attributes:
 
@@ -630,7 +632,7 @@ static RegisterPrimOp primop_fetchurl({
         characters that are invalid for the store.
 
       Not available in [restricted evaluation mode](@docroot@/command-ref/conf-file.md#conf-restrict-eval).
-    )",
+    )"_sds,
     .fun = prim_fetchurl,
 });
 
@@ -642,7 +644,7 @@ static void prim_fetchTarball(EvalState & state, const PosIdx pos, Value ** args
 static RegisterPrimOp primop_fetchTarball({
     .name = "fetchTarball",
     .args = {"args"},
-    .doc = R"(
+    .doc = &R"(
       Download the specified URL, unpack it and return the path of the
       unpacked tree. The file must be a tape archive (`.tar`) compressed
       with `gzip`, `bzip2` or `xz`. If the tarball consists of a
@@ -680,7 +682,7 @@ static RegisterPrimOp primop_fetchTarball({
       ```
 
       Not available in [restricted evaluation mode](@docroot@/command-ref/conf-file.md#conf-restrict-eval).
-    )",
+    )"_sds,
     .fun = prim_fetchTarball,
 });
 
@@ -693,7 +695,7 @@ static void prim_fetchGit(EvalState & state, const PosIdx pos, Value ** args, Va
 static RegisterPrimOp primop_fetchGit({
     .name = "fetchGit",
     .args = {"args"},
-    .doc = R"(
+    .doc = &R"(
       Fetch a path from git. *args* can be a URL, in which case the HEAD
       of the repo at that URL is fetched. Otherwise, it can be an
       attribute with the following attributes (all except `url` optional):
@@ -896,7 +898,7 @@ static RegisterPrimOp primop_fetchGit({
       given, `fetchGit` uses the current content of the checked-out
       files, even if they are not committed or added to Git's index. It
       only considers files added to the Git repository, as listed by `git ls-files`.
-    )",
+    )"_sds,
     .fun = prim_fetchGit,
 });
 

src/libexpr/primops/fromTOML.cc

@@ -1,6 +1,6 @@
 #include "nix/expr/primops.hh"
 #include "nix/expr/eval-inline.hh"
-#include "nix/expr/static-string-data.hh"
+#include "nix/expr/string-data-static.hh"
 
 #include "expr-config-private.hh"
 
@@ -170,10 +170,10 @@ static void prim_fromTOML(EvalState & state, const PosIdx pos, Value ** args, Va
     }
 }
 
-static RegisterPrimOp primop_fromTOML(
-    {.name = "fromTOML",
-     .args = {"e"},
-     .doc = R"(
+static RegisterPrimOp primop_fromTOML({
+    .name = "fromTOML",
+    .args = {"e"},
+    .doc = &R"(
       Convert a TOML string to a Nix value. For example,
 
       ```nix
@@ -186,7 +186,8 @@ static RegisterPrimOp primop_fromTOML(
       ```
 
       returns the value `{ s = "a"; table = { y = 2; }; x = 1; }`.
-    )",
-     .fun = prim_fromTOML});
+    )"_sds,
+    .fun = prim_fromTOML,
+});
 
 } // namespace nix

src/libfetchers-tests/git.cc

@@ -196,7 +196,7 @@ TEST_F(GitTest, submodulePeriodSupport)
             {"ref", "main"},
         });
 
-    auto [accessor, i] = input.getAccessor(store);
+    auto [accessor, i] = input.getAccessor(settings, store);
 
     ASSERT_EQ(accessor->readFile(CanonPath("deps/sub/lib.txt")), "hello from submodule\n");
 }

src/libfetchers/fetchers.cc

@@ -89,7 +89,7 @@ Input Input::fromAttrs(const Settings & settings, Attrs && attrs)
         // but not all of them. Doing this is to support those other
         // operations which are supposed to be robust on
         // unknown/uninterpretable inputs.
-        Input input{settings};
+        Input input;
         input.attrs = attrs;
         fixupInput(input);
         return input;
@@ -159,9 +159,9 @@ bool Input::isDirect() const
     return !scheme || scheme->isDirect(*this);
 }
 
-bool Input::isLocked() const
+bool Input::isLocked(const Settings & settings) const
 {
-    return scheme && scheme->isLocked(*this);
+    return scheme && scheme->isLocked(settings, *this);
 }
 
 bool Input::isFinal() const
@@ -198,17 +198,17 @@ bool Input::contains(const Input & other) const
 }
 
 // FIXME: remove
-std::pair<StorePath, Input> Input::fetchToStore(ref<Store> store) const
+std::pair<StorePath, Input> Input::fetchToStore(const Settings & settings, ref<Store> store) const
 {
     if (!scheme)
         throw Error("cannot fetch unsupported input '%s'", attrsToJSON(toAttrs()));
 
     auto [storePath, input] = [&]() -> std::pair<StorePath, Input> {
         try {
-            auto [accessor, result] = getAccessorUnchecked(store);
+            auto [accessor, result] = getAccessorUnchecked(settings, store);
 
             auto storePath =
-                nix::fetchToStore(*settings, *store, SourcePath(accessor), FetchMode::Copy, result.getName());
+                nix::fetchToStore(settings, *store, SourcePath(accessor), FetchMode::Copy, result.getName());
 
             auto narHash = store->queryPathInfo(storePath)->narHash;
             result.attrs.insert_or_assign("narHash", narHash.to_string(HashFormat::SRI, true));
@@ -297,10 +297,10 @@ void Input::checkLocks(Input specified, Input & result)
     }
 }
 
-std::pair<ref<SourceAccessor>, Input> Input::getAccessor(ref<Store> store) const
+std::pair<ref<SourceAccessor>, Input> Input::getAccessor(const Settings & settings, ref<Store> store) const
 {
     try {
-        auto [accessor, result] = getAccessorUnchecked(store);
+        auto [accessor, result] = getAccessorUnchecked(settings, store);
 
         result.attrs.insert_or_assign("__final", Explicit<bool>(true));
 
@@ -313,7 +313,7 @@ std::pair<ref<SourceAccessor>, Input> Input::getAccessor(ref<Store> store) const
     }
 }
 
-std::pair<ref<SourceAccessor>, Input> Input::getAccessorUnchecked(ref<Store> store) const
+std::pair<ref<SourceAccessor>, Input> Input::getAccessorUnchecked(const Settings & settings, ref<Store> store) const
 {
     // FIXME: cache the accessor
 
@@ -349,7 +349,7 @@ std::pair<ref<SourceAccessor>, Input> Input::getAccessorUnchecked(ref<Store> sto
             if (accessor->fingerprint) {
                 ContentAddressMethod method = ContentAddressMethod::Raw::NixArchive;
                 auto cacheKey = makeFetchToStoreCacheKey(getName(), *accessor->fingerprint, method, "/");
-                settings->getCache()->upsert(cacheKey, *store, {}, storePath);
+                settings.getCache()->upsert(cacheKey, *store, {}, storePath);
             }
 
             accessor->setPathDisplay("«" + to_string() + "»");
@@ -360,7 +360,7 @@ std::pair<ref<SourceAccessor>, Input> Input::getAccessorUnchecked(ref<Store> sto
         }
     }
 
-    auto [accessor, result] = scheme->getAccessor(store, *this);
+    auto [accessor, result] = scheme->getAccessor(settings, store, *this);
 
     if (!accessor->fingerprint)
         accessor->fingerprint = result.getFingerprint(store);
@@ -377,10 +377,10 @@ Input Input::applyOverrides(std::optional<std::string> ref, std::optional<Hash>
     return scheme->applyOverrides(*this, ref, rev);
 }
 
-void Input::clone(const Path & destDir) const
+void Input::clone(const Settings & settings, const Path & destDir) const
 {
     assert(scheme);
-    scheme->clone(*this, destDir);
+    scheme->clone(settings, *this, destDir);
 }
 
 std::optional<std::filesystem::path> Input::getSourcePath() const
@@ -493,7 +493,7 @@ void InputScheme::putFile(
     throw Error("input '%s' does not support modifying file '%s'", input.to_string(), path);
 }
 
-void InputScheme::clone(const Input & input, const Path & destDir) const
+void InputScheme::clone(const Settings & settings, const Input & input, const Path & destDir) const
 {
     throw Error("do not know how to clone input '%s'", input.to_string());
 }

src/libfetchers/git.cc

@@ -229,7 +229,7 @@ struct GitInputScheme : InputScheme
         if (auto ref = maybeGetStrAttr(attrs, "ref"); ref && !isLegalRefName(*ref))
             throw BadURL("invalid Git branch/tag name '%s'", *ref);
 
-        Input input{settings};
+        Input input{};
         input.attrs = attrs;
         input.attrs["url"] = fixGitURL(getStrAttr(attrs, "url")).to_string();
         getShallowAttr(input);
@@ -278,7 +278,7 @@ struct GitInputScheme : InputScheme
         return res;
     }
 
-    void clone(const Input & input, const Path & destDir) const override
+    void clone(const Settings & settings, const Input & input, const Path & destDir) const override
     {
         auto repoInfo = getRepoInfo(input);
 
@@ -623,7 +623,7 @@ struct GitInputScheme : InputScheme
     }
 
     std::pair<ref<SourceAccessor>, Input>
-    getAccessorFromCommit(ref<Store> store, RepoInfo & repoInfo, Input && input) const
+    getAccessorFromCommit(const Settings & settings, ref<Store> store, RepoInfo & repoInfo, Input && input) const
     {
         assert(!repoInfo.workdirInfo.isDirty);
 
@@ -733,10 +733,10 @@ struct GitInputScheme : InputScheme
 
         auto rev = *input.getRev();
 
-        input.attrs.insert_or_assign("lastModified", getLastModified(*input.settings, repoInfo, repoDir, rev));
+        input.attrs.insert_or_assign("lastModified", getLastModified(settings, repoInfo, repoDir, rev));
 
         if (!getShallowAttr(input))
-            input.attrs.insert_or_assign("revCount", getRevCount(*input.settings, repoInfo, repoDir, rev));
+            input.attrs.insert_or_assign("revCount", getRevCount(settings, repoInfo, repoDir, rev));
 
         printTalkative("using revision %s of repo '%s'", rev.gitRev(), repoInfo.locationToArg());
 
@@ -779,8 +779,8 @@ struct GitInputScheme : InputScheme
                 attrs.insert_or_assign("submodules", Explicit<bool>{true});
                 attrs.insert_or_assign("lfs", Explicit<bool>{smudgeLfs});
                 attrs.insert_or_assign("allRefs", Explicit<bool>{true});
-                auto submoduleInput = fetchers::Input::fromAttrs(*input.settings, std::move(attrs));
-                auto [submoduleAccessor, submoduleInput2] = submoduleInput.getAccessor(store);
+                auto submoduleInput = fetchers::Input::fromAttrs(settings, std::move(attrs));
+                auto [submoduleAccessor, submoduleInput2] = submoduleInput.getAccessor(settings, store);
                 submoduleAccessor->setPathDisplay("«" + submoduleInput.to_string() + "»");
                 mounts.insert_or_assign(submodule.path, submoduleAccessor);
             }
@@ -797,7 +797,7 @@ struct GitInputScheme : InputScheme
     }
 
     std::pair<ref<SourceAccessor>, Input>
-    getAccessorFromWorkdir(ref<Store> store, RepoInfo & repoInfo, Input && input) const
+    getAccessorFromWorkdir(const Settings & settings, ref<Store> store, RepoInfo & repoInfo, Input && input) const
     {
         auto repoPath = repoInfo.getPath().value();
 
@@ -829,8 +829,8 @@ struct GitInputScheme : InputScheme
                 // TODO: fall back to getAccessorFromCommit-like fetch when submodules aren't checked out
                 // attrs.insert_or_assign("allRefs", Explicit<bool>{ true });
 
-                auto submoduleInput = fetchers::Input::fromAttrs(*input.settings, std::move(attrs));
-                auto [submoduleAccessor, submoduleInput2] = submoduleInput.getAccessor(store);
+                auto submoduleInput = fetchers::Input::fromAttrs(settings, std::move(attrs));
+                auto [submoduleAccessor, submoduleInput2] = submoduleInput.getAccessor(settings, store);
                 submoduleAccessor->setPathDisplay("«" + submoduleInput.to_string() + "»");
 
                 /* If the submodule is dirty, mark this repo dirty as
@@ -857,12 +857,12 @@ struct GitInputScheme : InputScheme
             input.attrs.insert_or_assign("rev", rev.gitRev());
             if (!getShallowAttr(input)) {
                 input.attrs.insert_or_assign(
-                    "revCount", rev == nullRev ? 0 : getRevCount(*input.settings, repoInfo, repoPath, rev));
+                    "revCount", rev == nullRev ? 0 : getRevCount(settings, repoInfo, repoPath, rev));
             }
 
             verifyCommit(input, repo);
         } else {
-            repoInfo.warnDirty(*input.settings);
+            repoInfo.warnDirty(settings);
 
             if (repoInfo.workdirInfo.headRev) {
                 input.attrs.insert_or_assign("dirtyRev", repoInfo.workdirInfo.headRev->gitRev() + "-dirty");
@@ -874,14 +874,14 @@ struct GitInputScheme : InputScheme
 
         input.attrs.insert_or_assign(
             "lastModified",
-            repoInfo.workdirInfo.headRev
-                ? getLastModified(*input.settings, repoInfo, repoPath, *repoInfo.workdirInfo.headRev)
-                : 0);
+            repoInfo.workdirInfo.headRev ? getLastModified(settings, repoInfo, repoPath, *repoInfo.workdirInfo.headRev)
+                                         : 0);
 
         return {accessor, std::move(input)};
     }
 
-    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input>
+    getAccessor(const Settings & settings, ref<Store> store, const Input & _input) const override
     {
         Input input(_input);
 
@@ -897,8 +897,8 @@ struct GitInputScheme : InputScheme
         }
 
         auto [accessor, final] = input.getRef() || input.getRev() || !repoInfo.getPath()
-                                     ? getAccessorFromCommit(store, repoInfo, std::move(input))
-                                     : getAccessorFromWorkdir(store, repoInfo, std::move(input));
+                                     ? getAccessorFromCommit(settings, store, repoInfo, std::move(input))
+                                     : getAccessorFromWorkdir(settings, store, repoInfo, std::move(input));
 
         return {accessor, std::move(final)};
     }
@@ -934,7 +934,7 @@ struct GitInputScheme : InputScheme
         }
     }
 
-    bool isLocked(const Input & input) const override
+    bool isLocked(const Settings & settings, const Input & input) const override
     {
         auto rev = input.getRev();
         return rev && rev != nullRev;

src/libfetchers/github.cc

@@ -92,7 +92,7 @@ struct GitArchiveInputScheme : InputScheme
         if (ref && rev)
             throw BadURL("URL '%s' contains both a commit hash and a branch/tag name %s %s", url, *ref, rev->gitRev());
 
-        Input input{settings};
+        Input input{};
         input.attrs.insert_or_assign("type", std::string{schemeName()});
         input.attrs.insert_or_assign("owner", path[0]);
         input.attrs.insert_or_assign("repo", path[1]);
@@ -129,7 +129,7 @@ struct GitArchiveInputScheme : InputScheme
         getStrAttr(attrs, "owner");
         getStrAttr(attrs, "repo");
 
-        Input input{settings};
+        Input input{};
         input.attrs = attrs;
         return input;
     }
@@ -233,9 +233,9 @@ struct GitArchiveInputScheme : InputScheme
         std::optional<Hash> treeHash;
     };
 
-    virtual RefInfo getRevFromRef(nix::ref<Store> store, const Input & input) const = 0;
+    virtual RefInfo getRevFromRef(const Settings & settings, nix::ref<Store> store, const Input & input) const = 0;
 
-    virtual DownloadUrl getDownloadUrl(const Input & input) const = 0;
+    virtual DownloadUrl getDownloadUrl(const Settings & settings, const Input & input) const = 0;
 
     struct TarballInfo
     {
@@ -243,7 +243,7 @@ struct GitArchiveInputScheme : InputScheme
         time_t lastModified;
     };
 
-    std::pair<Input, TarballInfo> downloadArchive(ref<Store> store, Input input) const
+    std::pair<Input, TarballInfo> downloadArchive(const Settings & settings, ref<Store> store, Input input) const
     {
         if (!maybeGetStrAttr(input.attrs, "ref"))
             input.attrs.insert_or_assign("ref", "HEAD");
@@ -252,7 +252,7 @@ struct GitArchiveInputScheme : InputScheme
 
         auto rev = input.getRev();
         if (!rev) {
-            auto refInfo = getRevFromRef(store, input);
+            auto refInfo = getRevFromRef(settings, store, input);
             rev = refInfo.rev;
             upstreamTreeHash = refInfo.treeHash;
             debug("HEAD revision for '%s' is %s", input.to_string(), refInfo.rev.gitRev());
@@ -261,7 +261,7 @@ struct GitArchiveInputScheme : InputScheme
         input.attrs.erase("ref");
         input.attrs.insert_or_assign("rev", rev->gitRev());
 
-        auto cache = input.settings->getCache();
+        auto cache = settings.getCache();
 
         Cache::Key treeHashKey{"gitRevToTreeHash", {{"rev", rev->gitRev()}}};
         Cache::Key lastModifiedKey{"gitRevToLastModified", {{"rev", rev->gitRev()}}};
@@ -270,7 +270,7 @@ struct GitArchiveInputScheme : InputScheme
             if (auto lastModifiedAttrs = cache->lookup(lastModifiedKey)) {
                 auto treeHash = getRevAttr(*treeHashAttrs, "treeHash");
                 auto lastModified = getIntAttr(*lastModifiedAttrs, "lastModified");
-                if (input.settings->getTarballCache()->hasObject(treeHash))
+                if (settings.getTarballCache()->hasObject(treeHash))
                     return {std::move(input), TarballInfo{.treeHash = treeHash, .lastModified = (time_t) lastModified}};
                 else
                     debug("Git tree with hash '%s' has disappeared from the cache, refetching...", treeHash.gitRev());
@@ -278,7 +278,7 @@ struct GitArchiveInputScheme : InputScheme
         }
 
         /* Stream the tarball into the tarball cache. */
-        auto url = getDownloadUrl(input);
+        auto url = getDownloadUrl(settings, input);
 
         auto source = sinkToSource([&](Sink & sink) {
             FileTransferRequest req(url.url);
@@ -290,7 +290,7 @@ struct GitArchiveInputScheme : InputScheme
             *logger, lvlInfo, actUnknown, fmt("unpacking '%s' into the Git cache", input.to_string()));
 
         TarArchive archive{*source};
-        auto tarballCache = input.settings->getTarballCache();
+        auto tarballCache = settings.getTarballCache();
         auto parseSink = tarballCache->getFileSystemObjectSink();
         auto lastModified = unpackTarfileToSink(archive, *parseSink);
         auto tree = parseSink->flush();
@@ -315,9 +315,10 @@ struct GitArchiveInputScheme : InputScheme
         return {std::move(input), tarballInfo};
     }
 
-    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input>
+    getAccessor(const Settings & settings, ref<Store> store, const Input & _input) const override
     {
-        auto [input, tarballInfo] = downloadArchive(store, _input);
+        auto [input, tarballInfo] = downloadArchive(settings, store, _input);
 
 #if 0
         input.attrs.insert_or_assign("treeHash", tarballInfo.treeHash.gitRev());
@@ -325,19 +326,18 @@ struct GitArchiveInputScheme : InputScheme
         input.attrs.insert_or_assign("lastModified", uint64_t(tarballInfo.lastModified));
 
         auto accessor =
-            input.settings->getTarballCache()->getAccessor(tarballInfo.treeHash, false, "«" + input.to_string() + "»");
+            settings.getTarballCache()->getAccessor(tarballInfo.treeHash, false, "«" + input.to_string() + "»");
 
         return {accessor, input};
     }
 
-    bool isLocked(const Input & input) const override
+    bool isLocked(const Settings & settings, const Input & input) const override
     {
         /* Since we can't verify the integrity of the tarball from the
            Git revision alone, we also require a NAR hash for
            locking. FIXME: in the future, we may want to require a Git
            tree hash instead of a NAR hash. */
-        return input.getRev().has_value()
-               && (input.settings->trustTarballsFromGitForges || input.getNarHash().has_value());
+        return input.getRev().has_value() && (settings.trustTarballsFromGitForges || input.getNarHash().has_value());
     }
 
     std::optional<ExperimentalFeature> experimentalFeature() const override
@@ -387,7 +387,7 @@ struct GitHubInputScheme : GitArchiveInputScheme
         return getStrAttr(input.attrs, "repo");
     }
 
-    RefInfo getRevFromRef(nix::ref<Store> store, const Input & input) const override
+    RefInfo getRevFromRef(const Settings & settings, nix::ref<Store> store, const Input & input) const override
     {
         auto host = getHost(input);
         auto url = fmt(
@@ -397,9 +397,9 @@ struct GitHubInputScheme : GitArchiveInputScheme
             getRepo(input),
             *input.getRef());
 
-        Headers headers = makeHeadersWithAuthTokens(*input.settings, host, input);
+        Headers headers = makeHeadersWithAuthTokens(settings, host, input);
 
-        auto downloadResult = downloadFile(store, *input.settings, url, "source", headers);
+        auto downloadResult = downloadFile(store, settings, url, "source", headers);
         auto json = nlohmann::json::parse(
             store->requireStoreObjectAccessor(downloadResult.storePath)->readFile(CanonPath::root));
 
@@ -408,11 +408,11 @@ struct GitHubInputScheme : GitArchiveInputScheme
             .treeHash = Hash::parseAny(std::string{json["commit"]["tree"]["sha"]}, HashAlgorithm::SHA1)};
     }
 
-    DownloadUrl getDownloadUrl(const Input & input) const override
+    DownloadUrl getDownloadUrl(const Settings & settings, const Input & input) const override
     {
         auto host = getHost(input);
 
-        Headers headers = makeHeadersWithAuthTokens(*input.settings, host, input);
+        Headers headers = makeHeadersWithAuthTokens(settings, host, input);
 
         // If we have no auth headers then we default to the public archive
         // urls so we do not run into rate limits.
@@ -426,12 +426,12 @@ struct GitHubInputScheme : GitArchiveInputScheme
         return DownloadUrl{parseURL(url), headers};
     }
 
-    void clone(const Input & input, const Path & destDir) const override
+    void clone(const Settings & settings, const Input & input, const Path & destDir) const override
     {
         auto host = getHost(input);
-        Input::fromURL(*input.settings, fmt("git+https://%s/%s/%s.git", host, getOwner(input), getRepo(input)))
+        Input::fromURL(settings, fmt("git+https://%s/%s/%s.git", host, getOwner(input), getRepo(input)))
             .applyOverrides(input.getRef(), input.getRev())
-            .clone(destDir);
+            .clone(settings, destDir);
     }
 };
 
@@ -461,7 +461,7 @@ struct GitLabInputScheme : GitArchiveInputScheme
         return std::make_pair(token.substr(0, fldsplit), token.substr(fldsplit + 1));
     }
 
-    RefInfo getRevFromRef(nix::ref<Store> store, const Input & input) const override
+    RefInfo getRevFromRef(const Settings & settings, nix::ref<Store> store, const Input & input) const override
     {
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("gitlab.com");
         // See rate limiting note below
@@ -472,9 +472,9 @@ struct GitLabInputScheme : GitArchiveInputScheme
                 getStrAttr(input.attrs, "repo"),
                 *input.getRef());
 
-        Headers headers = makeHeadersWithAuthTokens(*input.settings, host, input);
+        Headers headers = makeHeadersWithAuthTokens(settings, host, input);
 
-        auto downloadResult = downloadFile(store, *input.settings, url, "source", headers);
+        auto downloadResult = downloadFile(store, settings, url, "source", headers);
         auto json = nlohmann::json::parse(
             store->requireStoreObjectAccessor(downloadResult.storePath)->readFile(CanonPath::root));
 
@@ -488,7 +488,7 @@ struct GitLabInputScheme : GitArchiveInputScheme
         }
     }
 
-    DownloadUrl getDownloadUrl(const Input & input) const override
+    DownloadUrl getDownloadUrl(const Settings & settings, const Input & input) const override
     {
         // This endpoint has a rate limit threshold that may be
         // server-specific and vary based whether the user is
@@ -503,19 +503,19 @@ struct GitLabInputScheme : GitArchiveInputScheme
                 getStrAttr(input.attrs, "repo"),
                 input.getRev()->to_string(HashFormat::Base16, false));
 
-        Headers headers = makeHeadersWithAuthTokens(*input.settings, host, input);
+        Headers headers = makeHeadersWithAuthTokens(settings, host, input);
         return DownloadUrl{parseURL(url), headers};
     }
 
-    void clone(const Input & input, const Path & destDir) const override
+    void clone(const Settings & settings, const Input & input, const Path & destDir) const override
     {
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("gitlab.com");
         // FIXME: get username somewhere
         Input::fromURL(
-            *input.settings,
+            settings,
             fmt("git+https://%s/%s/%s.git", host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo")))
             .applyOverrides(input.getRef(), input.getRev())
-            .clone(destDir);
+            .clone(settings, destDir);
     }
 };
 
@@ -536,7 +536,7 @@ struct SourceHutInputScheme : GitArchiveInputScheme
         // Once it is implemented, however, should work as expected.
     }
 
-    RefInfo getRevFromRef(nix::ref<Store> store, const Input & input) const override
+    RefInfo getRevFromRef(const Settings & settings, nix::ref<Store> store, const Input & input) const override
     {
         // TODO: In the future, when the sourcehut graphql API is implemented for mercurial
         // and with anonymous access, this method should use it instead.
@@ -547,11 +547,11 @@ struct SourceHutInputScheme : GitArchiveInputScheme
         auto base_url =
             fmt("https://%s/%s/%s", host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo"));
 
-        Headers headers = makeHeadersWithAuthTokens(*input.settings, host, input);
+        Headers headers = makeHeadersWithAuthTokens(settings, host, input);
 
         std::string refUri;
         if (ref == "HEAD") {
-            auto downloadFileResult = downloadFile(store, *input.settings, fmt("%s/HEAD", base_url), "source", headers);
+            auto downloadFileResult = downloadFile(store, settings, fmt("%s/HEAD", base_url), "source", headers);
             auto contents = store->requireStoreObjectAccessor(downloadFileResult.storePath)->readFile(CanonPath::root);
 
             auto remoteLine = git::parseLsRemoteLine(getLine(contents).first);
@@ -564,8 +564,7 @@ struct SourceHutInputScheme : GitArchiveInputScheme
         }
         std::regex refRegex(refUri);
 
-        auto downloadFileResult =
-            downloadFile(store, *input.settings, fmt("%s/info/refs", base_url), "source", headers);
+        auto downloadFileResult = downloadFile(store, settings, fmt("%s/info/refs", base_url), "source", headers);
         auto contents = store->requireStoreObjectAccessor(downloadFileResult.storePath)->readFile(CanonPath::root);
         std::istringstream is(contents);
 
@@ -583,7 +582,7 @@ struct SourceHutInputScheme : GitArchiveInputScheme
         return RefInfo{.rev = Hash::parseAny(*id, HashAlgorithm::SHA1)};
     }
 
-    DownloadUrl getDownloadUrl(const Input & input) const override
+    DownloadUrl getDownloadUrl(const Settings & settings, const Input & input) const override
     {
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("git.sr.ht");
         auto url =
@@ -593,18 +592,18 @@ struct SourceHutInputScheme : GitArchiveInputScheme
                 getStrAttr(input.attrs, "repo"),
                 input.getRev()->to_string(HashFormat::Base16, false));
 
-        Headers headers = makeHeadersWithAuthTokens(*input.settings, host, input);
+        Headers headers = makeHeadersWithAuthTokens(settings, host, input);
         return DownloadUrl{parseURL(url), headers};
     }
 
-    void clone(const Input & input, const Path & destDir) const override
+    void clone(const Settings & settings, const Input & input, const Path & destDir) const override
     {
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("git.sr.ht");
         Input::fromURL(
-            *input.settings,
+            settings,
             fmt("git+https://%s/%s/%s", host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo")))
             .applyOverrides(input.getRef(), input.getRev())
-            .clone(destDir);
+            .clone(settings, destDir);
     }
 };
 

src/libfetchers/include/nix/fetchers/fetchers.hh

@@ -36,13 +36,6 @@ struct Input
 {
     friend struct InputScheme;
 
-    const Settings * settings;
-
-    Input(const Settings & settings)
-        : settings{&settings}
-    {
-    }
-
     std::shared_ptr<InputScheme> scheme; // note: can be null
     Attrs attrs;
 
@@ -87,7 +80,7 @@ public:
      * attributes like a Git revision or NAR hash that uniquely
      * identify its contents.
      */
-    bool isLocked() const;
+    bool isLocked(const Settings & settings) const;
 
     /**
      * Only for relative path flakes, i.e. 'path:./foo', returns the
@@ -120,7 +113,7 @@ public:
      * Fetch the entire input into the Nix store, returning the
      * location in the Nix store and the locked input.
      */
-    std::pair<StorePath, Input> fetchToStore(ref<Store> store) const;
+    std::pair<StorePath, Input> fetchToStore(const Settings & settings, ref<Store> store) const;
 
     /**
      * Check the locking attributes in `result` against
@@ -140,17 +133,17 @@ public:
      * input without copying it to the store. Also return a possibly
      * unlocked input.
      */
-    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store) const;
+    std::pair<ref<SourceAccessor>, Input> getAccessor(const Settings & settings, ref<Store> store) const;
 
 private:
 
-    std::pair<ref<SourceAccessor>, Input> getAccessorUnchecked(ref<Store> store) const;
+    std::pair<ref<SourceAccessor>, Input> getAccessorUnchecked(const Settings & settings, ref<Store> store) const;
 
 public:
 
     Input applyOverrides(std::optional<std::string> ref, std::optional<Hash> rev) const;
 
-    void clone(const Path & destDir) const;
+    void clone(const Settings & settings, const Path & destDir) const;
 
     std::optional<std::filesystem::path> getSourcePath() const;
 
@@ -223,7 +216,7 @@ struct InputScheme
 
     virtual Input applyOverrides(const Input & input, std::optional<std::string> ref, std::optional<Hash> rev) const;
 
-    virtual void clone(const Input & input, const Path & destDir) const;
+    virtual void clone(const Settings & settings, const Input & input, const Path & destDir) const;
 
     virtual std::optional<std::filesystem::path> getSourcePath(const Input & input) const;
 
@@ -233,7 +226,8 @@ struct InputScheme
         std::string_view contents,
         std::optional<std::string> commitMsg) const;
 
-    virtual std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const = 0;
+    virtual std::pair<ref<SourceAccessor>, Input>
+    getAccessor(const Settings & settings, ref<Store> store, const Input & input) const = 0;
 
     /**
      * Is this `InputScheme` part of an experimental feature?
@@ -250,7 +244,7 @@ struct InputScheme
         return std::nullopt;
     }
 
-    virtual bool isLocked(const Input & input) const
+    virtual bool isLocked(const Settings & settings, const Input & input) const
     {
         return false;
     }

src/libfetchers/include/nix/fetchers/input-cache.hh

@@ -3,6 +3,7 @@
 namespace nix::fetchers {
 
 enum class UseRegistries : int;
+struct Settings;
 
 struct InputCache
 {
@@ -14,7 +15,8 @@ struct InputCache
         Attrs extraAttrs;
     };
 
-    CachedResult getAccessor(ref<Store> store, const Input & originalInput, UseRegistries useRegistries);
+    CachedResult
+    getAccessor(const Settings & settings, ref<Store> store, const Input & originalInput, UseRegistries useRegistries);
 
     struct CachedInput
     {

src/libfetchers/include/nix/fetchers/registry.hh

@@ -59,7 +59,7 @@ Path getUserRegistryPath();
 
 Registries getRegistries(const Settings & settings, ref<Store> store);
 
-void overrideRegistry(const Input & from, const Input & to, const Attrs & extraAttrs);
+void overrideRegistry(const Settings & settings, const Input & from, const Input & to, const Attrs & extraAttrs);
 
 enum class UseRegistries : int {
     No,
@@ -71,6 +71,7 @@ enum class UseRegistries : int {
  * Rewrite a flakeref using the registries. If `filter` is set, only
  * use the registries for which the filter function returns true.
  */
-std::pair<Input, Attrs> lookupInRegistries(ref<Store> store, const Input & input, UseRegistries useRegistries);
+std::pair<Input, Attrs>
+lookupInRegistries(const Settings & settings, ref<Store> store, const Input & input, UseRegistries useRegistries);
 
 } // namespace nix::fetchers

src/libfetchers/indirect.cc

@@ -44,7 +44,7 @@ struct IndirectInputScheme : InputScheme
 
         // FIXME: forbid query params?
 
-        Input input{settings};
+        Input input{};
         input.attrs.insert_or_assign("type", "indirect");
         input.attrs.insert_or_assign("id", id);
         if (rev)
@@ -76,7 +76,7 @@ struct IndirectInputScheme : InputScheme
         if (!std::regex_match(id, flakeRegex))
             throw BadURL("'%s' is not a valid flake ID", id);
 
-        Input input{settings};
+        Input input{};
         input.attrs = attrs;
         return input;
     }
@@ -106,7 +106,8 @@ struct IndirectInputScheme : InputScheme
         return input;
     }
 
-    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const override
+    std::pair<ref<SourceAccessor>, Input>
+    getAccessor(const Settings & settings, ref<Store> store, const Input & input) const override
     {
         throw Error("indirect input '%s' cannot be fetched directly", input.to_string());
     }

src/libfetchers/input-cache.cc

@@ -5,23 +5,23 @@
 
 namespace nix::fetchers {
 
-InputCache::CachedResult
-InputCache::getAccessor(ref<Store> store, const Input & originalInput, UseRegistries useRegistries)
+InputCache::CachedResult InputCache::getAccessor(
+    const Settings & settings, ref<Store> store, const Input & originalInput, UseRegistries useRegistries)
 {
     auto fetched = lookup(originalInput);
     Input resolvedInput = originalInput;
 
     if (!fetched) {
         if (originalInput.isDirect()) {
-            auto [accessor, lockedInput] = originalInput.getAccessor(store);
+            auto [accessor, lockedInput] = originalInput.getAccessor(settings, store);
             fetched.emplace(CachedInput{.lockedInput = lockedInput, .accessor = accessor});
         } else {
             if (useRegistries != UseRegistries::No) {
-                auto [res, extraAttrs] = lookupInRegistries(store, originalInput, useRegistries);
+                auto [res, extraAttrs] = lookupInRegistries(settings, store, originalInput, useRegistries);
                 resolvedInput = std::move(res);
                 fetched = lookup(resolvedInput);
                 if (!fetched) {
-                    auto [accessor, lockedInput] = resolvedInput.getAccessor(store);
+                    auto [accessor, lockedInput] = resolvedInput.getAccessor(settings, store);
                     fetched.emplace(
                         CachedInput{.lockedInput = lockedInput, .accessor = accessor, .extraAttrs = extraAttrs});
                 }

src/libfetchers/mercurial.cc

@@ -89,7 +89,7 @@ struct MercurialInputScheme : InputScheme
                 throw BadURL("invalid Mercurial branch/tag name '%s'", *ref);
         }
 
-        Input input{settings};
+        Input input{};
         input.attrs = attrs;
         return input;
     }
@@ -154,7 +154,7 @@ struct MercurialInputScheme : InputScheme
         return {isLocal, isLocal ? renderUrlPathEnsureLegal(url.path) : url.to_string()};
     }
 
-    StorePath fetchToStore(ref<Store> store, Input & input) const
+    StorePath fetchToStore(const Settings & settings, ref<Store> store, Input & input) const
     {
         auto origRev = input.getRev();
 
@@ -176,10 +176,10 @@ struct MercurialInputScheme : InputScheme
                 /* This is an unclean working tree. So copy all tracked
                    files. */
 
-                if (!input.settings->allowDirty)
+                if (!settings.allowDirty)
                     throw Error("Mercurial tree '%s' is unclean", actualUrl);
 
-                if (input.settings->warnDirty)
+                if (settings.warnDirty)
                     warn("Mercurial tree '%s' is unclean", actualUrl);
 
                 input.attrs.insert_or_assign("ref", chomp(runHg({"branch", "-R", actualUrl})));
@@ -240,13 +240,13 @@ struct MercurialInputScheme : InputScheme
         Cache::Key refToRevKey{"hgRefToRev", {{"url", actualUrl}, {"ref", *input.getRef()}}};
 
         if (!input.getRev()) {
-            if (auto res = input.settings->getCache()->lookupWithTTL(refToRevKey))
+            if (auto res = settings.getCache()->lookupWithTTL(refToRevKey))
                 input.attrs.insert_or_assign("rev", getRevAttr(*res, "rev").gitRev());
         }
 
         /* If we have a rev, check if we have a cached store path. */
         if (auto rev = input.getRev()) {
-            if (auto res = input.settings->getCache()->lookupStorePath(revInfoKey(*rev), *store))
+            if (auto res = settings.getCache()->lookupStorePath(revInfoKey(*rev), *store))
                 return makeResult(res->value, res->storePath);
         }
 
@@ -300,7 +300,7 @@ struct MercurialInputScheme : InputScheme
 
         /* Now that we have the rev, check the cache again for a
            cached store path. */
-        if (auto res = input.settings->getCache()->lookupStorePath(revInfoKey(rev), *store))
+        if (auto res = settings.getCache()->lookupStorePath(revInfoKey(rev), *store))
             return makeResult(res->value, res->storePath);
 
         Path tmpDir = createTempDir();
@@ -317,18 +317,19 @@ struct MercurialInputScheme : InputScheme
         });
 
         if (!origRev)
-            input.settings->getCache()->upsert(refToRevKey, {{"rev", rev.gitRev()}});
+            settings.getCache()->upsert(refToRevKey, {{"rev", rev.gitRev()}});
 
-        input.settings->getCache()->upsert(revInfoKey(rev), *store, infoAttrs, storePath);
+        settings.getCache()->upsert(revInfoKey(rev), *store, infoAttrs, storePath);
 
         return makeResult(infoAttrs, std::move(storePath));
     }
 
-    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input>
+    getAccessor(const Settings & settings, ref<Store> store, const Input & _input) const override
     {
         Input input(_input);
 
-        auto storePath = fetchToStore(store, input);
+        auto storePath = fetchToStore(settings, store, input);
         auto accessor = store->requireStoreObjectAccessor(storePath);
 
         accessor->setPathDisplay("«" + input.to_string() + "»");
@@ -336,7 +337,7 @@ struct MercurialInputScheme : InputScheme
         return {accessor, input};
     }
 
-    bool isLocked(const Input & input) const override
+    bool isLocked(const Settings & settings, const Input & input) const override
     {
         return (bool) input.getRev();
     }

src/libfetchers/path.cc

@@ -17,7 +17,7 @@ struct PathInputScheme : InputScheme
         if (url.authority && url.authority->host.size())
             throw Error("path URL '%s' should not have an authority ('%s')", url, *url.authority);
 
-        Input input{settings};
+        Input input{};
         input.attrs.insert_or_assign("type", "path");
         input.attrs.insert_or_assign("path", renderUrlPathEnsureLegal(url.path));
 
@@ -60,7 +60,7 @@ struct PathInputScheme : InputScheme
     {
         getStrAttr(attrs, "path");
 
-        Input input{settings};
+        Input input{};
         input.attrs = attrs;
         return input;
     }
@@ -101,7 +101,7 @@ struct PathInputScheme : InputScheme
             return path;
     }
 
-    bool isLocked(const Input & input) const override
+    bool isLocked(const Settings & settings, const Input & input) const override
     {
         return (bool) input.getNarHash();
     }
@@ -116,7 +116,8 @@ struct PathInputScheme : InputScheme
         throw Error("cannot fetch input '%s' because it uses a relative path", input.to_string());
     }
 
-    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input>
+    getAccessor(const Settings & settings, ref<Store> store, const Input & _input) const override
     {
         Input input(_input);
         auto path = getStrAttr(input.attrs, "path");
@@ -145,7 +146,7 @@ struct PathInputScheme : InputScheme
         auto info = store->queryPathInfo(*storePath);
         accessor->fingerprint =
             fmt("path:%s", store->queryPathInfo(*storePath)->narHash.to_string(HashFormat::SRI, true));
-        input.settings->getCache()->upsert(
+        settings.getCache()->upsert(
             makeFetchToStoreCacheKey(
                 input.getName(), *accessor->fingerprint, ContentAddressMethod::Raw::NixArchive, "/"),
             *store,

src/libfetchers/registry.cc

@@ -131,9 +131,9 @@ std::shared_ptr<Registry> getFlagRegistry(const Settings & settings)
     return flagRegistry;
 }
 
-void overrideRegistry(const Input & from, const Input & to, const Attrs & extraAttrs)
+void overrideRegistry(const Settings & settings, const Input & from, const Input & to, const Attrs & extraAttrs)
 {
-    getFlagRegistry(*from.settings)->add(from, to, extraAttrs);
+    getFlagRegistry(settings)->add(from, to, extraAttrs);
 }
 
 static std::shared_ptr<Registry> getGlobalRegistry(const Settings & settings, ref<Store> store)
@@ -172,7 +172,8 @@ Registries getRegistries(const Settings & settings, ref<Store> store)
     return registries;
 }
 
-std::pair<Input, Attrs> lookupInRegistries(ref<Store> store, const Input & _input, UseRegistries useRegistries)
+std::pair<Input, Attrs>
+lookupInRegistries(const Settings & settings, ref<Store> store, const Input & _input, UseRegistries useRegistries)
 {
     Attrs extraAttrs;
     int n = 0;
@@ -187,7 +188,7 @@ restart:
     if (n > 100)
         throw Error("cycle detected in flake registry for '%s'", input.to_string());
 
-    for (auto & registry : getRegistries(*input.settings, store)) {
+    for (auto & registry : getRegistries(settings, store)) {
         if (useRegistries == UseRegistries::Limited
             && !(registry->type == fetchers::Registry::Flag || registry->type == fetchers::Registry::Global))
             continue;

src/libfetchers/tarball.cc

@@ -224,7 +224,7 @@ ref<SourceAccessor> downloadTarball(ref<Store> store, const Settings & settings,
 
     auto input = Input::fromAttrs(settings, std::move(attrs));
 
-    return input.getAccessor(store).first;
+    return input.getAccessor(settings, store).first;
 }
 
 // An input scheme corresponding to a curl-downloadable resource.
@@ -252,7 +252,7 @@ struct CurlInputScheme : InputScheme
         if (!isValidURL(_url, requireTree))
             return std::nullopt;
 
-        Input input{settings};
+        Input input{};
 
         auto url = _url;
 
@@ -302,7 +302,7 @@ struct CurlInputScheme : InputScheme
 
     std::optional<Input> inputFromAttrs(const Settings & settings, const Attrs & attrs) const override
     {
-        Input input{settings};
+        Input input{};
         input.attrs = attrs;
 
         // input.locked = (bool) maybeGetStrAttr(input.attrs, "hash");
@@ -319,7 +319,7 @@ struct CurlInputScheme : InputScheme
         return url;
     }
 
-    bool isLocked(const Input & input) const override
+    bool isLocked(const Settings & settings, const Input & input) const override
     {
         return (bool) input.getNarHash();
     }
@@ -340,7 +340,8 @@ struct FileInputScheme : CurlInputScheme
                                                : (!requireTree && !hasTarballExtension(url)));
     }
 
-    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input>
+    getAccessor(const Settings & settings, ref<Store> store, const Input & _input) const override
     {
         auto input(_input);
 
@@ -348,7 +349,7 @@ struct FileInputScheme : CurlInputScheme
            the Nix store directly, since there is little deduplication
            benefit in using the Git cache for single big files like
            tarballs. */
-        auto file = downloadFile(store, *input.settings, getStrAttr(input.attrs, "url"), input.getName());
+        auto file = downloadFile(store, settings, getStrAttr(input.attrs, "url"), input.getName());
 
         auto narHash = store->queryPathInfo(file.storePath)->narHash;
         input.attrs.insert_or_assign("narHash", narHash.to_string(HashFormat::SRI, true));
@@ -377,15 +378,15 @@ struct TarballInputScheme : CurlInputScheme
                                                : (requireTree || hasTarballExtension(url)));
     }
 
-    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input>
+    getAccessor(const Settings & settings, ref<Store> store, const Input & _input) const override
     {
         auto input(_input);
 
-        auto result =
-            downloadTarball_(*input.settings, getStrAttr(input.attrs, "url"), {}, "«" + input.to_string() + "»");
+        auto result = downloadTarball_(settings, getStrAttr(input.attrs, "url"), {}, "«" + input.to_string() + "»");
 
         if (result.immutableUrl) {
-            auto immutableInput = Input::fromURL(*input.settings, *result.immutableUrl);
+            auto immutableInput = Input::fromURL(settings, *result.immutableUrl);
             // FIXME: would be nice to support arbitrary flakerefs
             // here, e.g. git flakes.
             if (immutableInput.getType() != "tarball")
@@ -398,9 +399,7 @@ struct TarballInputScheme : CurlInputScheme
 
         input.attrs.insert_or_assign(
             "narHash",
-            input.settings->getTarballCache()
-                ->treeHashToNarHash(*input.settings, result.treeHash)
-                .to_string(HashFormat::SRI, true));
+            settings.getTarballCache()->treeHashToNarHash(settings, result.treeHash).to_string(HashFormat::SRI, true));
 
         return {result.accessor, input};
     }

src/libflake/flake-primops.cc

@@ -19,6 +19,7 @@
 #include "nix/expr/eval-settings.hh"
 #include "nix/expr/symbol-table.hh"
 #include "nix/expr/value.hh"
+#include "nix/expr/string-data-static.hh"
 #include "nix/fetchers/attrs.hh"
 #include "nix/fetchers/fetchers.hh"
 #include "nix/util/configuration.hh"
@@ -38,7 +39,7 @@ PrimOp getFlake(const Settings & settings)
         std::string flakeRefS(
             state.forceStringNoCtx(*args[0], pos, "while evaluating the argument passed to builtins.getFlake"));
         auto flakeRef = nix::parseFlakeRef(state.fetchSettings, flakeRefS, {}, true);
-        if (state.settings.pureEval && !flakeRef.input.isLocked())
+        if (state.settings.pureEval && !flakeRef.input.isLocked(state.fetchSettings))
             throw Error(
                 "cannot call 'getFlake' on unlocked flake reference '%s', at %s (use --impure to override)",
                 flakeRefS,
@@ -62,7 +63,7 @@ PrimOp getFlake(const Settings & settings)
     return PrimOp{
         .name = "__getFlake",
         .args = {"args"},
-        .doc = R"(
+        .doc = &R"(
           Fetch a flake from a flake reference, and return its output attributes and some metadata. For example:
 
           ```nix
@@ -76,7 +77,7 @@ PrimOp getFlake(const Settings & settings)
           ```nix
           (builtins.getFlake "github:edolstra/dwarffs").rev
           ```
-        )",
+        )"_sds,
         .fun = prim_getFlake,
         .experimentalFeature = Xp::Flakes,
     };
@@ -104,7 +105,7 @@ static void prim_parseFlakeRef(EvalState & state, const PosIdx pos, Value ** arg
 nix::PrimOp parseFlakeRef({
     .name = "__parseFlakeRef",
     .args = {"flake-ref"},
-    .doc = R"(
+    .doc = &R"(
       Parse a flake reference, and return its exploded form.
 
       For example:
@@ -118,7 +119,7 @@ nix::PrimOp parseFlakeRef({
       ```nix
       { dir = "lib"; owner = "NixOS"; ref = "23.05"; repo = "nixpkgs"; type = "github"; }
       ```
-    )",
+    )"_sds,
     .fun = prim_parseFlakeRef,
     .experimentalFeature = Xp::Flakes,
 });
@@ -162,7 +163,7 @@ static void prim_flakeRefToString(EvalState & state, const PosIdx pos, Value **
 nix::PrimOp flakeRefToString({
     .name = "__flakeRefToString",
     .args = {"attrs"},
-    .doc = R"(
+    .doc = &R"(
       Convert a flake reference from attribute set format to URL format.
 
       For example:
@@ -178,7 +179,7 @@ nix::PrimOp flakeRefToString({
       ```nix
       "github:NixOS/nixpkgs/23.05?dir=lib"
       ```
-    )",
+    )"_sds,
     .fun = prim_flakeRefToString,
     .experimentalFeature = Xp::Flakes,
 });

src/libflake/flake.cc

@@ -372,7 +372,8 @@ static Flake getFlake(
     const InputAttrPath & lockRootAttrPath)
 {
     // Fetch a lazy tree first.
-    auto cachedInput = state.inputCache->getAccessor(state.store, originalRef.input, useRegistries);
+    auto cachedInput =
+        state.inputCache->getAccessor(state.fetchSettings, state.store, originalRef.input, useRegistries);
 
     auto subdir = fetchers::maybeGetStrAttr(cachedInput.extraAttrs, "dir").value_or(originalRef.subdir);
     auto resolvedRef = FlakeRef(std::move(cachedInput.resolvedInput), subdir);
@@ -388,7 +389,8 @@ static Flake getFlake(
         debug("refetching input '%s' due to self attribute", newLockedRef);
         // FIXME: need to remove attrs that are invalidated by the changed input attrs, such as 'narHash'.
         newLockedRef.input.attrs.erase("narHash");
-        auto cachedInput2 = state.inputCache->getAccessor(state.store, newLockedRef.input, fetchers::UseRegistries::No);
+        auto cachedInput2 = state.inputCache->getAccessor(
+            state.fetchSettings, state.store, newLockedRef.input, fetchers::UseRegistries::No);
         cachedInput.accessor = cachedInput2.accessor;
         lockedRef = FlakeRef(std::move(cachedInput2.lockedInput), newLockedRef.subdir);
     }
@@ -704,7 +706,8 @@ lockFlake(const Settings & settings, EvalState & state, const FlakeRef & topRef,
                            this input. */
                         debug("creating new input '%s'", inputAttrPathS);
 
-                        if (!lockFlags.allowUnlocked && !input.ref->input.isLocked() && !input.ref->input.isRelative())
+                        if (!lockFlags.allowUnlocked && !input.ref->input.isLocked(state.fetchSettings)
+                            && !input.ref->input.isRelative())
                             throw Error("cannot update unlocked flake input '%s' in pure mode", inputAttrPathS);
 
                         /* Note: in case of an --override-input, we use
@@ -753,7 +756,7 @@ lockFlake(const Settings & settings, EvalState & state, const FlakeRef & topRef,
                                     return {*resolvedPath, *input.ref};
                                 } else {
                                     auto cachedInput = state.inputCache->getAccessor(
-                                        state.store, input.ref->input, useRegistriesInputs);
+                                        state.fetchSettings, state.store, input.ref->input, useRegistriesInputs);
 
                                     auto lockedRef = FlakeRef(std::move(cachedInput.lockedInput), input.ref->subdir);
 

src/libflake/flakeref.cc

@@ -64,9 +64,10 @@ std::ostream & operator<<(std::ostream & str, const FlakeRef & flakeRef)
     return str;
 }
 
-FlakeRef FlakeRef::resolve(ref<Store> store, fetchers::UseRegistries useRegistries) const
+FlakeRef FlakeRef::resolve(
+    const fetchers::Settings & fetchSettings, ref<Store> store, fetchers::UseRegistries useRegistries) const
 {
-    auto [input2, extraAttrs] = lookupInRegistries(store, input, useRegistries);
+    auto [input2, extraAttrs] = lookupInRegistries(fetchSettings, store, input, useRegistries);
     return FlakeRef(std::move(input2), fetchers::maybeGetStrAttr(extraAttrs, "dir").value_or(subdir));
 }
 
@@ -287,9 +288,10 @@ FlakeRef FlakeRef::fromAttrs(const fetchers::Settings & fetchSettings, const fet
         fetchers::maybeGetStrAttr(attrs, "dir").value_or(""));
 }
 
-std::pair<ref<SourceAccessor>, FlakeRef> FlakeRef::lazyFetch(ref<Store> store) const
+std::pair<ref<SourceAccessor>, FlakeRef>
+FlakeRef::lazyFetch(const fetchers::Settings & fetchSettings, ref<Store> store) const
 {
-    auto [accessor, lockedInput] = input.getAccessor(store);
+    auto [accessor, lockedInput] = input.getAccessor(fetchSettings, store);
     return {accessor, FlakeRef(std::move(lockedInput), subdir)};
 }
 

src/libflake/include/nix/flake/flakeref.hh

@@ -71,11 +71,15 @@ struct FlakeRef
 
     fetchers::Attrs toAttrs() const;
 
-    FlakeRef resolve(ref<Store> store, fetchers::UseRegistries useRegistries = fetchers::UseRegistries::All) const;
+    FlakeRef resolve(
+        const fetchers::Settings & fetchSettings,
+        ref<Store> store,
+        fetchers::UseRegistries useRegistries = fetchers::UseRegistries::All) const;
 
     static FlakeRef fromAttrs(const fetchers::Settings & fetchSettings, const fetchers::Attrs & attrs);
 
-    std::pair<ref<SourceAccessor>, FlakeRef> lazyFetch(ref<Store> store) const;
+    std::pair<ref<SourceAccessor>, FlakeRef>
+    lazyFetch(const fetchers::Settings & fetchSettings, ref<Store> store) const;
 
     /**
      * Canonicalize a flakeref for the purpose of comparing "old" and

src/libflake/lockfile.cc

@@ -74,7 +74,7 @@ LockedNode::LockedNode(const fetchers::Settings & fetchSettings, const nlohmann:
     , parentInputAttrPath(
           json.find("parent") != json.end() ? (std::optional<InputAttrPath>) json["parent"] : std::nullopt)
 {
-    if (!lockedRef.input.isLocked() && !lockedRef.input.isRelative()) {
+    if (!lockedRef.input.isLocked(fetchSettings) && !lockedRef.input.isRelative()) {
         if (lockedRef.input.getNarHash())
             warn(
                 "Lock file entry '%s' is unlocked (e.g. lacks a Git revision) but is checked by NAR hash. "
@@ -282,7 +282,7 @@ std::optional<FlakeRef> LockFile::isUnlocked(const fetchers::Settings & fetchSet
        latter case, we can verify the input but we may not be able to
        fetch it from anywhere. */
     auto isConsideredLocked = [&](const fetchers::Input & input) {
-        return input.isLocked() || (fetchSettings.allowDirtyLocks && input.getNarHash());
+        return input.isLocked(fetchSettings) || (fetchSettings.allowDirtyLocks && input.getNarHash());
     };
 
     for (auto & i : nodes) {

src/libstore/local-store.cc

@@ -1385,7 +1385,6 @@ bool LocalStore::verifyStore(bool checkContents, RepairFlag repair)
             checkInterrupt();
             auto name = link.path().filename();
             printMsg(lvlTalkative, "checking contents of %s", name);
-            PosixSourceAccessor accessor;
             std::string hash = hashPath(
                                    PosixSourceAccessor::createAtRoot(link.path()),
                                    FileIngestionMethod::NixArchive,

src/libutil-tests/monitorfdhup.cc

@@ -1,4 +1,5 @@
-#ifndef _WIN32
+// TODO: investigate why this is hanging on cygwin
+#if !defined(_WIN32) && !defined(__CYGWIN__)
 
 #  include "nix/util/util.hh"
 #  include "nix/util/monitor-fd.hh"

src/libutil/archive.cc

@@ -103,9 +103,9 @@ void SourceAccessor::dumpPath(const CanonPath & path, Sink & sink, PathFilter &
 
 time_t dumpPathAndGetMtime(const Path & path, Sink & sink, PathFilter & filter)
 {
-    auto path2 = PosixSourceAccessor::createAtRoot(path);
+    auto path2 = PosixSourceAccessor::createAtRoot(path, /*trackLastModified=*/true);
     path2.dumpPath(sink, filter);
-    return path2.accessor.dynamic_pointer_cast<PosixSourceAccessor>()->mtime;
+    return path2.accessor->getLastModified().value();
 }
 
 void dumpPath(const Path & path, Sink & sink, PathFilter & filter)

src/libutil/include/nix/util/canon-path.hh

@@ -8,6 +8,7 @@
 #include <iostream>
 #include <set>
 #include <vector>
+#include <ranges>
 
 #include <boost/container_hash/hash.hpp>
 
@@ -122,33 +123,70 @@ public:
         return &cs[1];
     }
 
-    struct Iterator
+    class Iterator
     {
+        /**
+         * Helper class with overloaded operator-> for "drill-down" behavior.
+         * This was a "temporary" string_view doesn't have to be stored anywhere.
+         */
+        class PointerProxy
+        {
+            std::string_view segment;
+
+        public:
+            PointerProxy(std::string_view segment_)
+                : segment(segment_)
+            {
+            }
+
+            const std::string_view * operator->() const
+            {
+                return &segment;
+            }
+        };
+
+    public:
+        using value_type = std::string_view;
+        using reference_type = const std::string_view;
+        using pointer_type = PointerProxy;
+        using difference_type = std::ptrdiff_t;
+        using iterator_category = std::forward_iterator_tag;
+
         std::string_view remaining;
         size_t slash;
 
+        /**
+         * Dummy default constructor required for forward iterators. Doesn't return
+         * a usable iterator.
+         */
+        Iterator()
+            : remaining()
+            , slash(0)
+        {
+        }
+
         Iterator(std::string_view remaining)
             : remaining(remaining)
             , slash(remaining.find('/'))
         {
         }
 
-        bool operator!=(const Iterator & x) const
-        {
-            return remaining.data() != x.remaining.data();
-        }
-
         bool operator==(const Iterator & x) const
         {
-            return !(*this != x);
+            return remaining.data() == x.remaining.data();
         }
 
-        const std::string_view operator*() const
+        reference_type operator*() const
         {
             return remaining.substr(0, slash);
         }
 
-        void operator++()
+        pointer_type operator->() const
+        {
+            return PointerProxy(**this);
+        }
+
+        Iterator & operator++()
         {
             if (slash == remaining.npos)
                 remaining = remaining.substr(remaining.size());
@@ -156,9 +194,19 @@ public:
                 remaining = remaining.substr(slash + 1);
                 slash = remaining.find('/');
             }
+            return *this;
+        }
+
+        Iterator operator++(int)
+        {
+            auto tmp = *this;
+            ++*this;
+            return tmp;
         }
     };
 
+    static_assert(std::forward_iterator<Iterator>);
+
     Iterator begin() const
     {
         return Iterator(rel());
@@ -265,6 +313,8 @@ public:
     friend std::size_t hash_value(const CanonPath &);
 };
 
+static_assert(std::ranges::forward_range<CanonPath>);
+
 std::ostream & operator<<(std::ostream & stream, const CanonPath & path);
 
 inline std::size_t hash_value(const CanonPath & path)

src/libutil/include/nix/util/posix-source-accessor.hh

@@ -9,7 +9,7 @@ struct SourcePath;
 /**
  * A source accessor that uses the Unix filesystem.
  */
-struct PosixSourceAccessor : virtual SourceAccessor
+class PosixSourceAccessor : virtual public SourceAccessor
 {
     /**
      * Optional root path to prefix all operations into the native file
@@ -18,8 +18,12 @@ struct PosixSourceAccessor : virtual SourceAccessor
      */
     const std::filesystem::path root;
 
+    const bool trackLastModified = false;
+
+public:
+
     PosixSourceAccessor();
-    PosixSourceAccessor(std::filesystem::path && root);
+    PosixSourceAccessor(std::filesystem::path && root, bool trackLastModified = false);
 
     /**
      * The most recent mtime seen by lstat(). This is a hack to
@@ -43,6 +47,9 @@ struct PosixSourceAccessor : virtual SourceAccessor
      * Create a `PosixSourceAccessor` and `SourcePath` corresponding to
      * some native path.
      *
+     * @param Whether the accessor should return a non-null getLastModified.
+     * When true the accessor must be used only by a single thread.
+     *
      * The `PosixSourceAccessor` is rooted as far up the tree as
      * possible, (e.g. on Windows it could scoped to a drive like
      * `C:\`). This allows more `..` parent accessing to work.
@@ -64,7 +71,12 @@ struct PosixSourceAccessor : virtual SourceAccessor
      * and
      * [`std::filesystem::path::relative_path`](https://en.cppreference.com/w/cpp/filesystem/path/relative_path).
      */
-    static SourcePath createAtRoot(const std::filesystem::path & path);
+    static SourcePath createAtRoot(const std::filesystem::path & path, bool trackLastModified = false);
+
+    std::optional<std::time_t> getLastModified() override
+    {
+        return trackLastModified ? std::optional{mtime} : std::nullopt;
+    }
 
 private:
 

src/libutil/include/nix/util/util.hh

@@ -33,15 +33,28 @@ auto concatStrings(Parts &&... parts)
     return concatStringsSep({}, views);
 }
 
+/**
+ * Add quotes around a string.
+ */
+inline std::string quoteString(std::string_view s, char quote = '\'')
+{
+    std::string result;
+    result.reserve(s.size() + 2);
+    result += quote;
+    result += s;
+    result += quote;
+    return result;
+}
+
 /**
  * Add quotes around a collection of strings.
  */
 template<class C>
-Strings quoteStrings(const C & c)
+Strings quoteStrings(const C & c, char quote = '\'')
 {
     Strings res;
     for (auto & s : c)
-        res.push_back("'" + s + "'");
+        res.push_back(quoteString(s, quote));
     return res;
 }
 

src/libutil/posix-source-accessor.cc

@@ -7,8 +7,9 @@
 
 namespace nix {
 
-PosixSourceAccessor::PosixSourceAccessor(std::filesystem::path && argRoot)
+PosixSourceAccessor::PosixSourceAccessor(std::filesystem::path && argRoot, bool trackLastModified)
     : root(std::move(argRoot))
+    , trackLastModified(trackLastModified)
 {
     assert(root.empty() || root.is_absolute());
     displayPrefix = root.string();
@@ -19,11 +20,11 @@ PosixSourceAccessor::PosixSourceAccessor()
 {
 }
 
-SourcePath PosixSourceAccessor::createAtRoot(const std::filesystem::path & path)
+SourcePath PosixSourceAccessor::createAtRoot(const std::filesystem::path & path, bool trackLastModified)
 {
     std::filesystem::path path2 = absPath(path);
     return {
-        make_ref<PosixSourceAccessor>(path2.root_path()),
+        make_ref<PosixSourceAccessor>(path2.root_path(), trackLastModified),
         CanonPath{path2.relative_path().string()},
     };
 }
@@ -114,9 +115,12 @@ std::optional<SourceAccessor::Stat> PosixSourceAccessor::maybeLstat(const CanonP
     auto st = cachedLstat(path);
     if (!st)
         return std::nullopt;
-    // This makes the accessor thread-unsafe, but we only seem to use the actual value in a single threaded context in
-    // `src/libfetchers/path.cc`.
-    mtime = std::max(mtime, st->st_mtime);
+
+    /* The contract is that trackLastModified implies that the caller uses the accessor
+       from a single thread. Thus this is not a CAS loop. */
+    if (trackLastModified)
+        mtime = std::max(mtime, st->st_mtime);
+
     return Stat{
         .type = S_ISREG(st->st_mode)   ? tRegular
                 : S_ISDIR(st->st_mode) ? tDirectory

src/nix/flake-prefetch-inputs.cc

@@ -45,7 +45,7 @@ struct CmdFlakePrefetchInputs : FlakeCommand
             if (auto lockedNode = dynamic_cast<const LockedNode *>(&node)) {
                 try {
                     Activity act(*logger, lvlInfo, actUnknown, fmt("fetching '%s'", lockedNode->lockedRef));
-                    auto accessor = lockedNode->lockedRef.input.getAccessor(store).first;
+                    auto accessor = lockedNode->lockedRef.input.getAccessor(fetchSettings, store).first;
                     fetchToStore(
                         fetchSettings, *store, accessor, FetchMode::Copy, lockedNode->lockedRef.input.getName());
                 } catch (Error & e) {

src/nix/flake.cc

@@ -245,7 +245,7 @@ struct CmdFlakeMetadata : FlakeCommand, MixJSON
             printJSON(j);
         } else {
             logger->cout(ANSI_BOLD "Resolved URL:" ANSI_NORMAL "  %s", flake.resolvedRef.to_string());
-            if (flake.lockedRef.input.isLocked())
+            if (flake.lockedRef.input.isLocked(fetchSettings))
                 logger->cout(ANSI_BOLD "Locked URL:" ANSI_NORMAL "    %s", flake.lockedRef.to_string());
             if (flake.description)
                 logger->cout(ANSI_BOLD "Description:" ANSI_NORMAL "   %s", *flake.description);
@@ -1049,7 +1049,7 @@ struct CmdFlakeClone : FlakeCommand
         if (destDir.empty())
             throw Error("missing flag '--dest'");
 
-        getFlakeRef().resolve(store).input.clone(destDir);
+        getFlakeRef().resolve(fetchSettings, store).input.clone(fetchSettings, destDir);
     }
 };
 
@@ -1100,7 +1100,7 @@ struct CmdFlakeArchive : FlakeCommand, MixJSON, MixDryRun, MixNoCheckSigs
                     std::optional<StorePath> storePath;
                     if (!(*inputNode)->lockedRef.input.isRelative()) {
                         storePath = dryRun ? (*inputNode)->lockedRef.input.computeStorePath(*store)
-                                           : (*inputNode)->lockedRef.input.fetchToStore(store).first;
+                                           : (*inputNode)->lockedRef.input.fetchToStore(fetchSettings, store).first;
                         sources.insert(*storePath);
                     }
                     if (json) {
@@ -1324,8 +1324,10 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                         try {
                             if (visitor.isDerivation())
                                 showDerivation();
-                            else
-                                throw Error("expected a derivation");
+                            else {
+                                auto name = visitor.getAttrPathStr(state->s.name);
+                                logger->warn(fmt("%s is not a derivation", name));
+                            }
                         } catch (IFDError & e) {
                             if (!json) {
                                 logger->cout(
@@ -1496,8 +1498,8 @@ struct CmdFlakePrefetch : FlakeCommand, MixJSON
     void run(ref<Store> store) override
     {
         auto originalRef = getFlakeRef();
-        auto resolvedRef = originalRef.resolve(store);
-        auto [accessor, lockedRef] = resolvedRef.lazyFetch(store);
+        auto resolvedRef = originalRef.resolve(fetchSettings, store);
+        auto [accessor, lockedRef] = resolvedRef.lazyFetch(getEvalState()->fetchSettings, store);
         auto storePath =
             fetchToStore(getEvalState()->fetchSettings, *store, accessor, FetchMode::Copy, lockedRef.input.getName());
         auto hash = store->queryPathInfo(storePath)->narHash;

src/nix/main.cc

@@ -440,7 +440,7 @@ void mainWrapped(int argc, char ** argv)
             if (!primOp->doc)
                 continue;
             b["args"] = primOp->args;
-            b["doc"] = trim(stripIndentation(primOp->doc));
+            b["doc"] = trim(stripIndentation(primOp->doc->view()));
             if (primOp->experimentalFeature)
                 b["experimental-feature"] = primOp->experimentalFeature;
             builtinsJson.emplace(state.symbols[builtin.name], std::move(b));
@@ -449,7 +449,7 @@ void mainWrapped(int argc, char ** argv)
             auto b = nlohmann::json::object();
             if (!info.doc)
                 continue;
-            b["doc"] = trim(stripIndentation(info.doc));
+            b["doc"] = trim(stripIndentation(info.doc->view()));
             b["type"] = showType(info.type, false);
             if (info.impureOnly)
                 b["impure-only"] = true;

src/nix/nix-env/user-env.cc

@@ -9,7 +9,7 @@
 #include "nix/expr/eval-inline.hh"
 #include "nix/store/profiles.hh"
 #include "nix/expr/print-ambiguous.hh"
-#include "nix/expr/static-string-data.hh"
+#include "nix/expr/string-data-static.hh"
 
 #include <limits>
 #include <sstream>

src/nix/profile.cc

@@ -711,7 +711,7 @@ struct CmdProfileUpgrade : virtual SourceExprCommand, MixDefaultProfile, MixProf
                     element.identifier());
                 continue;
             }
-            if (element.source->originalRef.input.isLocked()) {
+            if (element.source->originalRef.input.isLocked(getEvalState()->fetchSettings)) {
                 warn(
                     "Found package '%s', but it was added from a locked flake reference so it can't be upgraded!",
                     element.identifier());
@@ -740,7 +740,8 @@ struct CmdProfileUpgrade : virtual SourceExprCommand, MixDefaultProfile, MixProf
             assert(infop);
             auto & info = *infop;
 
-            if (info.flake.lockedRef.input.isLocked() && element.source->lockedRef == info.flake.lockedRef)
+            if (info.flake.lockedRef.input.isLocked(getEvalState()->fetchSettings)
+                && element.source->lockedRef == info.flake.lockedRef)
                 continue;
 
             printInfo(

src/nix/registry.cc

@@ -190,8 +190,9 @@ struct CmdRegistryPin : RegistryCommand, EvalCommand
         auto ref = parseFlakeRef(fetchSettings, url);
         auto lockedRef = parseFlakeRef(fetchSettings, locked);
         registry->remove(ref.input);
-        auto resolved = lockedRef.resolve(store).input.getAccessor(store).second;
-        if (!resolved.isLocked())
+        auto resolvedInput = lockedRef.resolve(fetchSettings, store).input;
+        auto resolved = resolvedInput.getAccessor(fetchSettings, store).second;
+        if (!resolved.isLocked(fetchSettings))
             warn("flake '%s' is not locked", resolved.to_string());
         fetchers::Attrs extraAttrs;
         if (ref.subdir != "")

tests/functional/flakes/show.sh

@@ -107,3 +107,26 @@ in
 assert show_output.packages.${builtins.currentSystem}.default == { };
 true
 '
+
+
+# Test that nix keeps going even when packages.$SYSTEM contains not derivations
+cat >flake.nix <<EOF
+{
+  outputs = inputs: {
+    packages.$system = {
+      drv1 = import ./simple.nix;
+      not-a-derivation = 42;
+      drv2 = import ./simple.nix;
+    };
+  };
+}
+EOF
+nix flake show --json --all-systems > show-output.json
+# shellcheck disable=SC2016
+nix eval --impure --expr '
+let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
+in
+assert show_output.packages.${builtins.currentSystem}.not-a-derivation == {};
+true
+'
+