Merge branch 'master' into overlayfs-store

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v25
+    - uses: cachix/install-nix-action@v26
       with:
         # The sandbox would otherwise be disabled by default on Darwin
         extra_nix_config: "sandbox = true"
@@ -62,7 +62,7 @@ jobs:
       with:
         fetch-depth: 0
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v25
+    - uses: cachix/install-nix-action@v26
       with:
         install_url: https://releases.nixos.org/nix/nix-2.20.3/install
     - uses: cachix/cachix-action@v14
@@ -84,7 +84,7 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v25
+    - uses: cachix/install-nix-action@v26
       with:
         install_url: '${{needs.installer.outputs.installerURL}}'
         install_options: "--tarball-url-prefix https://${{ env.CACHIX_NAME }}.cachix.org/serve"
@@ -114,7 +114,7 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v25
+    - uses: cachix/install-nix-action@v26
       with:
         install_url: https://releases.nixos.org/nix/nix-2.20.3/install
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
@@ -157,4 +157,5 @@ jobs:
         docker push $IMAGE_ID:$NIX_VERSION
         docker push $IMAGE_ID:latest
         # deprecated 2024-02-24
+        docker tag nix:$NIX_VERSION $IMAGE_ID:master
         docker push $IMAGE_ID:master

.gitignore

@@ -10,6 +10,7 @@ perl/Makefile.config
 /stamp-h1
 /svn-revision
 /libtool
+/config/config.*
 
 # /doc/manual/
 /doc/manual/*.1

.version

@@ -1 +1 @@
-2.21.0
+2.22.0

CONTRIBUTING.md

@@ -67,7 +67,7 @@ Check out the [security policy](https://github.com/NixOS/nix/security/policy).
    - [ ] API documentation in header files
    - [ ] Code and comments are self-explanatory
    - [ ] Commit message explains **why** the change was made
-   - [ ] New feature or incompatible change: updated [release notes](./doc/manual/src/release-notes/rl-next.md)
+   - [ ] New feature or incompatible change: [add a release note](https://nixos.org/manual/nix/stable/contributing/hacking#add-a-release-note)
 
 7. If you need additional feedback or help to getting pull request into shape, ask other contributors using [@mentions](https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#mentioning-people-and-teams).
 

doc/manual/redirects.js

@@ -14,7 +14,7 @@
 
 const redirects = {
  "index.html": {
-    "part-advanced-topics": "advanced-topics/advanced-topics.html",
+    "part-advanced-topics": "advanced-topics/index.html",
     "chap-tuning-cores-and-jobs": "advanced-topics/cores-vs-jobs.html",
     "chap-diff-hook": "advanced-topics/diff-hook.html",
     "check-dirs-are-unregistered": "advanced-topics/diff-hook.html#check-dirs-are-unregistered",
@@ -22,7 +22,7 @@ const redirects = {
     "chap-post-build-hook": "advanced-topics/post-build-hook.html",
     "chap-post-build-hook-caveats": "advanced-topics/post-build-hook.html#implementation-caveats",
     "chap-writing-nix-expressions": "language/index.html",
-    "part-command-ref": "command-ref/command-ref.html",
+    "part-command-ref": "command-ref/index.html",
     "conf-allow-import-from-derivation": "command-ref/conf-file.html#conf-allow-import-from-derivation",
     "conf-allow-new-privileges": "command-ref/conf-file.html#conf-allow-new-privileges",
     "conf-allowed-uris": "command-ref/conf-file.html#conf-allowed-uris",
@@ -261,7 +261,7 @@ const redirects = {
     "sec-installer-proxy-settings": "installation/env-variables.html#proxy-environment-variables",
     "sec-nix-ssl-cert-file": "installation/env-variables.html#nix_ssl_cert_file",
     "sec-nix-ssl-cert-file-with-nix-daemon-and-macos": "installation/env-variables.html#nix_ssl_cert_file-with-macos-and-the-nix-daemon",
-    "chap-installation": "installation/installation.html",
+    "chap-installation": "installation/index.html",
     "ch-installing-binary": "installation/installing-binary.html",
     "sect-macos-installation": "installation/installing-binary.html#macos-installation",
     "sect-macos-installation-change-store-prefix": "installation/installing-binary.html#macos-installation",
@@ -288,7 +288,7 @@ const redirects = {
     "ssec-copy-closure": "package-management/copy-closure.html",
     "sec-garbage-collection": "package-management/garbage-collection.html",
     "ssec-gc-roots": "package-management/garbage-collector-roots.html",
-    "chap-package-management": "package-management/package-management.html",
+    "chap-package-management": "package-management/index.html",
     "sec-profiles": "package-management/profiles.html",
     "ssec-s3-substituter": "package-management/s3-substituter.html",
     "ssec-s3-substituter-anonymous-reads": "package-management/s3-substituter.html#anonymous-reads-to-your-s3-compatible-binary-cache",
@@ -297,7 +297,7 @@ const redirects = {
     "sec-sharing-packages": "package-management/sharing-packages.html",
     "ssec-ssh-substituter": "package-management/ssh-substituter.html",
     "chap-quick-start": "quick-start.html",
-    "sec-relnotes": "release-notes/release-notes.html",
+    "sec-relnotes": "release-notes/index.html",
     "ch-relnotes-0.10.1": "release-notes/rl-0.10.1.html",
     "ch-relnotes-0.10": "release-notes/rl-0.10.html",
     "ssec-relnotes-0.11": "release-notes/rl-0.11.html",

doc/manual/rl-next/better-errors-in-nix-repl.md

@@ -1,40 +0,0 @@
----
-synopsis: Concise error printing in `nix repl`
-prs: 9928
----
-
-Previously, if an element of a list or attribute set threw an error while
-evaluating, `nix repl` would print the entire error (including source location
-information) inline. This output was clumsy and difficult to parse:
-
-```
-nix-repl> { err = builtins.throw "uh oh!"; }
-{ err = «error:
-       … while calling the 'throw' builtin
-         at «string»:1:9:
-            1| { err = builtins.throw "uh oh!"; }
-             |         ^
-
-       error: uh oh!»; }
-```
-
-Now, only the error message is displayed, making the output much more readable.
-```
-nix-repl> { err = builtins.throw "uh oh!"; }
-{ err = «error: uh oh!»; }
-```
-
-However, if the whole expression being evaluated throws an error, source
-locations and (if applicable) a stack trace are printed, just like you'd expect:
-
-```
-nix-repl> builtins.throw "uh oh!"
-error:
-       … while calling the 'throw' builtin
-         at «string»:1:1:
-            1| builtins.throw "uh oh!"
-             | ^
-
-       error: uh oh!
-```
-

doc/manual/rl-next/debugger-locals-for-let-expressions.md

@@ -1,9 +0,0 @@
----
-synopsis: "`--debugger` can now access bindings from `let` expressions"
-prs: 9918
-issues: 8827.
----
-
-Breakpoints and errors in the bindings of a `let` expression can now access
-those bindings in the debugger. Previously, only the body of `let` expressions
-could access those bindings.

doc/manual/rl-next/debugger-on-trace.md

@@ -1,9 +0,0 @@
----
-synopsis: Enter the `--debugger` when `builtins.trace` is called if `debugger-on-trace` is set
-prs: 9914
----
-
-If the `debugger-on-trace` option is set and `--debugger` is given,
-`builtins.trace` calls will behave similarly to `builtins.break` and will enter
-the debug REPL. This is useful for determining where warnings are being emitted
-from.

doc/manual/rl-next/debugger-positions.md

@@ -1,25 +0,0 @@
----
-synopsis: Debugger prints source position information
-prs: 9913
----
-
-The `--debugger` now prints source location information, instead of the
-pointers of source location information. Before:
-
-```
-nix-repl> :bt
-0: while evaluating the attribute 'python311.pythonForBuild.pkgs'
-0x600001522598
-```
-
-After:
-
-```
-0: while evaluating the attribute 'python311.pythonForBuild.pkgs'
-/nix/store/hg65h51xnp74ikahns9hyf3py5mlbbqq-source/overrides/default.nix:132:27
-
-   131|
-   132|       bootstrappingBase = pkgs.${self.python.pythonAttr}.pythonForBuild.pkgs;
-      |                           ^
-   133|     in
-```

doc/manual/rl-next/enter-debugger-more-reliably-in-let-and-calls.md

@@ -1,25 +0,0 @@
----
-synopsis: The `--debugger` will start more reliably in `let` expressions and function calls
-prs: 9917
-issues: 6649
----
-
-Previously, if you attempted to evaluate this file with the debugger:
-
-```nix
-let
-  a = builtins.trace "before inner break" (
-    builtins.break "hello"
-  );
-  b = builtins.trace "before outer break" (
-    builtins.break a
-  );
-in
-  b
-```
-
-Nix would correctly enter the debugger at `builtins.break a`, but if you asked
-it to `:continue`, it would skip over the `builtins.break "hello"` expression
-entirely.
-
-Now, Nix will correctly enter the debugger at both breakpoints.

doc/manual/rl-next/inherit-from-by-need.md

@@ -1,7 +0,0 @@
----
-synopsis: "`inherit (x) ...` evaluates `x` only once"
-prs: 9847
----
-
-`inherit (x) a b ...` now evaluates the expression `x` only once for all inherited attributes rather than once for each inherited attribute.
-This does not usually have a measurable impact, but side-effects (such as `builtins.trace`) would be duplicated and expensive expressions (such as derivations) could cause a measurable slowdown.

doc/manual/rl-next/lambda-printing.md

@@ -1,50 +0,0 @@
----
-synopsis: Functions are printed with more detail
-prs: 9606
-issues: 7145
----
-
-Functions and `builtins` are printed with more detail in `nix repl`, `nix
-eval`, `builtins.trace`, and most other places values are printed.
-
-Before:
-
-```
-$ nix repl nixpkgs
-nix-repl> builtins.map
-«primop»
-
-nix-repl> builtins.map lib.id
-«primop-app»
-
-nix-repl> builtins.trace lib.id "my-value"
-trace: <LAMBDA>
-"my-value"
-
-$ nix eval --file functions.nix
-{ id = <LAMBDA>; primop = <PRIMOP>; primop-app = <PRIMOP-APP>; }
-```
-
-After:
-
-```
-$ nix repl nixpkgs
-nix-repl> builtins.map
-«primop map»
-
-nix-repl> builtins.map lib.id
-«partially applied primop map»
-
-nix-repl> builtins.trace lib.id "my-value"
-trace: «lambda id @ /nix/store/8rrzq23h2zq7sv5l2vhw44kls5w0f654-source/lib/trivial.nix:26:5»
-"my-value"
-
-$ nix eval --file functions.nix
-{ id = «lambda id @ /Users/wiggles/nix/functions.nix:2:8»; primop = «primop map»; primop-app = «partially applied primop map»; }
-```
-
-This was actually released in Nix 2.20, but wasn't added to the release notes
-so we're announcing it here. The historical release notes have been updated as well.
-
-[type-error]: https://github.com/NixOS/nix/pull/9753
-[coercion-error]: https://github.com/NixOS/nix/pull/9754

doc/manual/rl-next/leading-period.md

@@ -1,10 +0,0 @@
----
-synopsis: Store paths are allowed to start with `.`
-issues: 912
-prs: 9867 9091 9095 9120 9121 9122 9130 9219 9224
----
-
-Leading periods were allowed by accident in Nix 2.4. The Nix team has considered this to be a bug, but this behavior has since been relied on by users, leading to unnecessary difficulties.
-From now on, leading periods are officially, definitively supported. The names `.` and `..` are disallowed, as well as those starting with `.-` or `..-`.
-
-Nix versions that denied leading periods are documented [in the issue](https://github.com/NixOS/nix/issues/912#issuecomment-1919583286).

doc/manual/rl-next/more-commands-respect-ctrl-c.md

@@ -1,13 +0,0 @@
----
-synopsis: Nix commands respect Ctrl-C
-prs: 9687 6995
-issues: 7245
----
-
-Previously, many Nix commands would hang indefinitely if Ctrl-C was pressed
-while performing various operations (including `nix develop`, `nix flake
-update`, and so on). With several fixes to Nix's signal handlers, Nix commands
-will now exit quickly after Ctrl-C is pressed.
-
-This was actually released in Nix 2.20, but wasn't added to the release notes
-so we're announcing it here. The historical release notes have been updated as well.

doc/manual/rl-next/nix-eval-derivations.md

@@ -0,0 +1,13 @@
+---
+synopsis: "`nix eval` prints derivations as `.drv` paths"
+prs: 10200
+---
+
+`nix eval` will now print derivations as their `.drv` paths, rather than as
+attribute sets. This makes commands like `nix eval nixpkgs#bash` terminate
+instead of infinitely looping into recursive self-referential attributes:
+
+```ShellSession
+$ nix eval nixpkgs#bash
+«derivation /nix/store/m32cbgbd598f4w299g0hwyv7gbw6rqcg-bash-5.2p26.drv»
+```

doc/manual/rl-next/pretty-print-in-nix-repl.md

@@ -1,24 +0,0 @@
----
-synopsis: "`nix repl` pretty-prints values"
-prs: 9931
----
-
-`nix repl` will now pretty-print values:
-
-```
-{
-  attrs = {
-    a = {
-      b = {
-        c = { };
-      };
-    };
-  };
-  list = [ 1 ];
-  list' = [
-    1
-    2
-    3
-  ];
-}
-```

doc/manual/rl-next/reduce-debugger-clutter.md

@@ -1,37 +0,0 @@
----
-synopsis: "Visual clutter in `--debugger` is reduced"
-prs: 9919
----
-
-Before:
-```
-info: breakpoint reached
-
-
-Starting REPL to allow you to inspect the current state of the evaluator.
-
-Welcome to Nix 2.20.0pre20231222_dirty. Type :? for help.
-
-nix-repl> :continue
-error: uh oh
-
-
-Starting REPL to allow you to inspect the current state of the evaluator.
-
-Welcome to Nix 2.20.0pre20231222_dirty. Type :? for help.
-
-nix-repl>
-```
-
-After:
-
-```
-info: breakpoint reached
-
-Nix 2.20.0pre20231222_dirty debugger
-Type :? for help.
-nix-repl> :continue
-error: uh oh
-
-nix-repl>
-```

doc/manual/rl-next/repl-ctrl-c-while-printing.md

@@ -1,8 +0,0 @@
----
-synopsis: "`nix repl` now respects Ctrl-C while printing values"
-prs: 9927
----
-
-`nix repl` will now halt immediately when Ctrl-C is pressed while it's printing
-a value. This is useful if you got curious about what would happen if you
-printed all of Nixpkgs.

doc/manual/rl-next/repl-cycle-detection.md

@@ -1,22 +0,0 @@
----
-synopsis: Cycle detection in `nix repl` is simpler and more reliable
-prs: 9926
-issues: 8672
----
-
-The cycle detection in `nix repl`, `nix eval`, `builtins.trace`, and everywhere
-else values are printed is now simpler and matches the cycle detection in
-`nix-instantiate --eval` output.
-
-Before:
-
-```
-nix eval --expr 'let self = { inherit self; }; in self'
-{ self = { self = «repeated»; }; }
-```
-
-After:
-
-```
-{ self = «repeated»; }
-```

doc/manual/rl-next/source-location-in-while-evaluating-attribute.md

@@ -1,23 +0,0 @@
----
-synopsis: "In the debugger, `while evaluating the attribute` errors now include position information"
-prs: 9915
----
-
-Before:
-
-```
-0: while evaluating the attribute 'python311.pythonForBuild.pkgs'
-0x600001522598
-```
-
-After:
-
-```
-0: while evaluating the attribute 'python311.pythonForBuild.pkgs'
-/nix/store/hg65h51xnp74ikahns9hyf3py5mlbbqq-source/overrides/default.nix:132:27
-
-   131|
-   132|       bootstrappingBase = pkgs.${self.python.pythonAttr}.pythonForBuild.pkgs;
-      |                           ^
-   133|     in
-```

doc/manual/rl-next/stack-size-macos.md

@@ -1,9 +0,0 @@
----
-synopsis: Stack size is increased on macOS
-prs: 9860
----
-
-Previously, Nix would set the stack size to 64MiB on Linux, but would leave the
-stack size set to the default (approximately 8KiB) on macOS. Now, the stack
-size is correctly set to 64MiB on macOS as well, which should reduce stack
-overflow segfaults in deeply-recursive Nix expressions.

doc/manual/src/SUMMARY.md.in

@@ -121,6 +121,7 @@
   - [C++ style guide](contributing/cxx.md)
 - [Release Notes](release-notes/index.md)
 {{#include ./SUMMARY-rl-next.md}}
+  - [Release 2.21 (2024-03-11)](release-notes/rl-2.21.md)
   - [Release 2.20 (2024-01-29)](release-notes/rl-2.20.md)
   - [Release 2.19 (2023-11-17)](release-notes/rl-2.19.md)
   - [Release 2.18 (2023-09-20)](release-notes/rl-2.18.md)

doc/manual/src/glossary.md

@@ -86,7 +86,7 @@
 
   [store path]: #gloss-store-path
 
-- [file system object]{#gloss-store-object}
+- [file system object]{#gloss-file-system-object}
 
   The Nix data model for representing simplified file system data.
 

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

@@ -188,9 +188,13 @@ Derivations can declare some infrequently used optional attributes.
     }
     ```
 
-    The `outputHashAlgo` attribute specifies the hash algorithm used to
+    The `outputHash` attribute must be a string containing the hash in either hexadecimal or "nix32" encoding, or following the format for integrity metadata as defined by [SRI](https://www.w3.org/TR/SRI/).
-    compute the hash. It can currently be `"sha1"`, `"sha256"` or
+    The "nix32" encoding is an adaptation of base-32 encoding.
-    `"sha512"`.
+    The [`convertHash`](@docroot@/language/builtins.md#builtins-convertHash) function shows how to convert between different encodings, and the [`nix-hash` command](../command-ref/nix-hash.md) has information about obtaining the hash for some contents, as well as converting to and from encodings.
+
+    The `outputHashAlgo` attribute specifies the hash algorithm used to compute the hash.
+    It can currently be `"sha1"`, `"sha256"`, `"sha512"`, or `null`.
+    `outputHashAlgo` can only be `null` when `outputHash` follows the SRI format.
 
     The `outputHashMode` attribute determines how the hash is computed.
     It must be one of the following two values:
@@ -209,11 +213,6 @@ Derivations can declare some infrequently used optional attributes.
         this case, the output can be anything, including a directory
         tree.
 
-    The `outputHash` attribute, finally, must be a string containing
-    the hash in either hexadecimal or base-32 notation. (See the
-    [`nix-hash` command](../command-ref/nix-hash.md) for information
-    about converting to and from base-32 notation.)
-
   - [`__contentAddressed`]{#adv-attr-__contentAddressed}
     > **Warning**
     > This attribute is part of an [experimental feature](@docroot@/contributing/experimental-features.md).

doc/manual/src/language/index.md

@@ -432,6 +432,32 @@ This is an incomplete overview of language features, by example.
 
   </td>
  </tr>
+ <tr>
+  <td>
+
+   `inherit pkgs src;`
+
+  </td>
+  <td>
+
+   Adds the variables to the current scope (attribute set or `let` binding).
+   Desugars to `pkgs = pkgs; src = src;`
+
+  </td>
+ </tr>
+ <tr>
+  <td>
+
+   `inherit (pkgs) lib stdenv;`
+
+  </td>
+  <td>
+
+   Adds the attributes, from the attribute set in parentheses, to the current scope (attribute set or `let` binding).
+   Desugars to `lib = pkgs.lib; stdenv = pkgs.stdenv;`
+
+  </td>
+ </tr>
  <tr>
   <td>
 

doc/manual/src/quick-start.md

@@ -34,7 +34,7 @@ For more in-depth information you are kindly referred to subsequent chapters.
    lolcat: command not found
    ```
 
-1. Search for more packages on <search.nixos.org> to try them out.
+1. Search for more packages on [search.nixos.org](https://search.nixos.org/) to try them out.
 
 1. Free up storage space:
 

doc/manual/src/release-notes/rl-2.21.md

@@ -0,0 +1,302 @@
+# Release 2.21.0 (2024-03-11)
+
+- Fix a fixed-output derivation sandbox escape (CVE-2024-27297)
+
+  Cooperating Nix derivations could send file descriptors to files in the Nix
+  store to each other via Unix domain sockets in the abstract namespace. This
+  allowed one derivation to modify the output of the other derivation, after Nix
+  has registered the path as "valid" and immutable in the Nix database.
+  In particular, this allowed the output of fixed-output derivations to be
+  modified from their expected content.
+
+  This isn't the case any more.
+
+- CLI options `--arg-from-file` and `--arg-from-stdin` [#10122](https://github.com/NixOS/nix/pull/10122)
+
+  The new CLI option `--arg-from-file` *name* *path* passes the contents
+  of file *path* as a string value via the function argument *name* to a
+  Nix expression. Similarly, the new option `--arg-from-stdin` *name*
+  reads the contents of the string from standard input.
+
+- Concise error printing in `nix repl` [#9928](https://github.com/NixOS/nix/pull/9928)
+
+  Previously, if an element of a list or attribute set threw an error while
+  evaluating, `nix repl` would print the entire error (including source location
+  information) inline. This output was clumsy and difficult to parse:
+
+  ```
+  nix-repl> { err = builtins.throw "uh oh!"; }
+  { err = «error:
+         … while calling the 'throw' builtin
+           at «string»:1:9:
+              1| { err = builtins.throw "uh oh!"; }
+               |         ^
+
+         error: uh oh!»; }
+  ```
+
+  Now, only the error message is displayed, making the output much more readable.
+  ```
+  nix-repl> { err = builtins.throw "uh oh!"; }
+  { err = «error: uh oh!»; }
+  ```
+
+  However, if the whole expression being evaluated throws an error, source
+  locations and (if applicable) a stack trace are printed, just like you'd expect:
+
+  ```
+  nix-repl> builtins.throw "uh oh!"
+  error:
+         … while calling the 'throw' builtin
+           at «string»:1:1:
+              1| builtins.throw "uh oh!"
+               | ^
+
+         error: uh oh!
+  ```
+
+- `--debugger` can now access bindings from `let` expressions [#8827](https://github.com/NixOS/nix/issues/8827) [#9918](https://github.com/NixOS/nix/pull/9918)
+
+  Breakpoints and errors in the bindings of a `let` expression can now access
+  those bindings in the debugger. Previously, only the body of `let` expressions
+  could access those bindings.
+
+- Enter the `--debugger` when `builtins.trace` is called if `debugger-on-trace` is set [#9914](https://github.com/NixOS/nix/pull/9914)
+
+  If the `debugger-on-trace` option is set and `--debugger` is given,
+  `builtins.trace` calls will behave similarly to `builtins.break` and will enter
+  the debug REPL. This is useful for determining where warnings are being emitted
+  from.
+
+- Debugger prints source position information [#9913](https://github.com/NixOS/nix/pull/9913)
+
+  The `--debugger` now prints source location information, instead of the
+  pointers of source location information. Before:
+
+  ```
+  nix-repl> :bt
+  0: while evaluating the attribute 'python311.pythonForBuild.pkgs'
+  0x600001522598
+  ```
+
+  After:
+
+  ```
+  0: while evaluating the attribute 'python311.pythonForBuild.pkgs'
+  /nix/store/hg65h51xnp74ikahns9hyf3py5mlbbqq-source/overrides/default.nix:132:27
+
+     131|
+     132|       bootstrappingBase = pkgs.${self.python.pythonAttr}.pythonForBuild.pkgs;
+        |                           ^
+     133|     in
+  ```
+
+- The `--debugger` will start more reliably in `let` expressions and function calls [#6649](https://github.com/NixOS/nix/issues/6649) [#9917](https://github.com/NixOS/nix/pull/9917)
+
+  Previously, if you attempted to evaluate this file with the debugger:
+
+  ```nix
+  let
+    a = builtins.trace "before inner break" (
+      builtins.break "hello"
+    );
+    b = builtins.trace "before outer break" (
+      builtins.break a
+    );
+  in
+    b
+  ```
+
+  Nix would correctly enter the debugger at `builtins.break a`, but if you asked
+  it to `:continue`, it would skip over the `builtins.break "hello"` expression
+  entirely.
+
+  Now, Nix will correctly enter the debugger at both breakpoints.
+
+- Nested debuggers are no longer supported [#9920](https://github.com/NixOS/nix/pull/9920)
+
+  Previously, evaluating an expression that throws an error in the debugger would
+  enter a second, nested debugger:
+
+  ```
+  nix-repl> builtins.throw "what"
+  error: what
+
+
+  Starting REPL to allow you to inspect the current state of the evaluator.
+
+  Welcome to Nix 2.18.1. Type :? for help.
+
+  nix-repl>
+  ```
+
+  Now, it just prints the error message like `nix repl`:
+
+  ```
+  nix-repl> builtins.throw "what"
+  error:
+         … while calling the 'throw' builtin
+           at «string»:1:1:
+              1| builtins.throw "what"
+               | ^
+
+         error: what
+  ```
+
+- Consistent order of function arguments in printed expressions [#9874](https://github.com/NixOS/nix/pull/9874)
+
+  Function arguments are now printed in lexicographic order rather than the internal, creation-time based symbol order.
+
+- Fix duplicate attribute error positions for `inherit` [#9874](https://github.com/NixOS/nix/pull/9874)
+
+  When an `inherit` caused a duplicate attribute error the position of the error was not reported correctly, placing the error with the inherit itself or at the start of the bindings block instead of the offending attribute name.
+
+- `inherit (x) ...` evaluates `x` only once [#9847](https://github.com/NixOS/nix/pull/9847)
+
+  `inherit (x) a b ...` now evaluates the expression `x` only once for all inherited attributes rather than once for each inherited attribute.
+  This does not usually have a measurable impact, but side-effects (such as `builtins.trace`) would be duplicated and expensive expressions (such as derivations) could cause a measurable slowdown.
+
+- Store paths are allowed to start with `.` [#912](https://github.com/NixOS/nix/issues/912) [#9091](https://github.com/NixOS/nix/pull/9091) [#9095](https://github.com/NixOS/nix/pull/9095) [#9120](https://github.com/NixOS/nix/pull/9120) [#9121](https://github.com/NixOS/nix/pull/9121) [#9122](https://github.com/NixOS/nix/pull/9122) [#9130](https://github.com/NixOS/nix/pull/9130) [#9219](https://github.com/NixOS/nix/pull/9219) [#9224](https://github.com/NixOS/nix/pull/9224) [#9867](https://github.com/NixOS/nix/pull/9867)
+
+  Leading periods were allowed by accident in Nix 2.4. The Nix team has considered this to be a bug, but this behavior has since been relied on by users, leading to unnecessary difficulties.
+  From now on, leading periods are supported. The names `.` and `..` are disallowed, as well as those starting with `.-` or `..-`.
+
+  Nix versions that denied leading periods are documented [in the issue](https://github.com/NixOS/nix/issues/912#issuecomment-1919583286).
+
+- `nix repl` pretty-prints values [#9931](https://github.com/NixOS/nix/pull/9931)
+
+  `nix repl` will now pretty-print values:
+
+  ```
+  {
+    attrs = {
+      a = {
+        b = {
+          c = { };
+        };
+      };
+    };
+    list = [ 1 ];
+    list' = [
+      1
+      2
+      3
+    ];
+  }
+  ```
+
+- Introduction of `--regex` and `--all` in `nix profile remove` and `nix profile upgrade` [#10166](https://github.com/NixOS/nix/pull/10166)
+
+  Previously the command-line arguments for `nix profile remove` and `nix profile upgrade` matched the package entries using regular expression.
+  For instance:
+
+  ```
+  nix profile remove '.*vim.*'
+  ```
+
+  This would remove all packages that contain `vim` in their name.
+
+  In most cases, only singular package names were used to remove and upgrade packages. Mixing this with regular expressions sometimes lead to unintended behavior. For instance, `python3.1` could match `python311`.
+
+  To avoid unintended behavior, the arguments are now only matching exact names.
+
+  Matching using regular expressions is still possible by using the new `--regex` flag:
+
+  ```
+  nix profile remove --regex '.*vim.*'
+  ```
+
+  One of the most useful cases for using regular expressions was to upgrade all packages. This was previously accomplished by:
+
+  ```
+  nix profile upgrade '.*'
+  ```
+
+  With the introduction of the `--all` flag, this now becomes more straightforward:
+
+  ```
+  nix profile upgrade --all
+  ```
+
+- Visual clutter in `--debugger` is reduced [#9919](https://github.com/NixOS/nix/pull/9919)
+
+  Before:
+  ```
+  info: breakpoint reached
+
+
+  Starting REPL to allow you to inspect the current state of the evaluator.
+
+  Welcome to Nix 2.20.0pre20231222_dirty. Type :? for help.
+
+  nix-repl> :continue
+  error: uh oh
+
+
+  Starting REPL to allow you to inspect the current state of the evaluator.
+
+  Welcome to Nix 2.20.0pre20231222_dirty. Type :? for help.
+
+  nix-repl>
+  ```
+
+  After:
+
+  ```
+  info: breakpoint reached
+
+  Nix 2.20.0pre20231222_dirty debugger
+  Type :? for help.
+  nix-repl> :continue
+  error: uh oh
+
+  nix-repl>
+  ```
+
+- Cycle detection in `nix repl` is simpler and more reliable [#8672](https://github.com/NixOS/nix/issues/8672) [#9926](https://github.com/NixOS/nix/pull/9926)
+
+  The cycle detection in `nix repl`, `nix eval`, `builtins.trace`, and everywhere
+  else values are printed is now simpler and matches the cycle detection in
+  `nix-instantiate --eval` output.
+
+  Before:
+
+  ```
+  nix eval --expr 'let self = { inherit self; }; in self'
+  { self = { self = «repeated»; }; }
+  ```
+
+  After:
+
+  ```
+  { self = «repeated»; }
+  ```
+
+- In the debugger, `while evaluating the attribute` errors now include position information [#9915](https://github.com/NixOS/nix/pull/9915)
+
+  Before:
+
+  ```
+  0: while evaluating the attribute 'python311.pythonForBuild.pkgs'
+  0x600001522598
+  ```
+
+  After:
+
+  ```
+  0: while evaluating the attribute 'python311.pythonForBuild.pkgs'
+  /nix/store/hg65h51xnp74ikahns9hyf3py5mlbbqq-source/overrides/default.nix:132:27
+
+     131|
+     132|       bootstrappingBase = pkgs.${self.python.pythonAttr}.pythonForBuild.pkgs;
+        |                           ^
+     133|     in
+  ```
+
+- Stack size is increased on macOS [#9860](https://github.com/NixOS/nix/pull/9860)
+
+  Previously, Nix would set the stack size to 64MiB on Linux, but would leave the
+  stack size set to the default (approximately 8KiB) on macOS. Now, the stack
+  size is correctly set to 64MiB on macOS as well, which should reduce stack
+  overflow segfaults in deeply-recursive Nix expressions.
+

flake.nix

@@ -31,7 +31,6 @@
       crossSystems = [
         "armv6l-unknown-linux-gnueabihf"
         "armv7l-unknown-linux-gnueabihf"
-        "x86_64-unknown-freebsd13"
         "x86_64-unknown-netbsd"
       ];
 
@@ -299,8 +298,11 @@
               ''
                 type -p nix-env
                 # Note: we're filtering out nixos-install-tools because https://github.com/NixOS/nixpkgs/pull/153594#issuecomment-1020530593.
-                time nix-env --store dummy:// -f ${nixpkgs-regression} -qaP --drv-path | sort | grep -v nixos-install-tools > packages
+                (
-                [[ $(sha1sum < packages | cut -c1-40) = ff451c521e61e4fe72bdbe2d0ca5d1809affa733 ]]
+                  set -x
+                  time nix-env --store dummy:// -f ${nixpkgs-regression} -qaP --drv-path | sort | grep -v nixos-install-tools > packages
+                  [[ $(sha1sum < packages | cut -c1-40) = e01b031fc9785a572a38be6bc473957e3b6faad7 ]]
+                )
                 mkdir $out
               '';
 
@@ -341,7 +343,6 @@
 
       checks = forAllSystems (system: {
         binaryTarball = self.hydraJobs.binaryTarball.${system};
-        perlBindings = self.hydraJobs.perlBindings.${system};
         installTests = self.hydraJobs.installTests.${system};
         nixpkgsLibTests = self.hydraJobs.tests.nixpkgsLibTests.${system};
         rl-next =
@@ -351,6 +352,11 @@
         '';
       } // (lib.optionalAttrs (builtins.elem system linux64BitSystems)) {
         dockerImage = self.hydraJobs.dockerImage.${system};
+      } // (lib.optionalAttrs (!(builtins.elem system linux32BitSystems))) {
+        # Some perl dependencies are broken on i686-linux.
+        # Since the support is only best-effort there, disable the perl
+        # bindings
+        perlBindings = self.hydraJobs.perlBindings.${system};
       });
 
       packages = forAllSystems (system: rec {

maintainers/upload-release.pl

@@ -11,6 +11,8 @@ use JSON::PP;
 use LWP::UserAgent;
 use Net::Amazon::S3;
 
+delete $ENV{'shell'}; # shut up a LWP::UserAgent.pm warning
+
 my $evalId = $ARGV[0] or die "Usage: $0 EVAL-ID\n";
 
 my $releasesBucketName = "nix-releases";
@@ -36,9 +38,9 @@ sub fetch {
 my $evalUrl = "https://hydra.nixos.org/eval/$evalId";
 my $evalInfo = decode_json(fetch($evalUrl, 'application/json'));
 #print Dumper($evalInfo);
-my $flakeUrl = $evalInfo->{flake} or die;
+my $flakeUrl = $evalInfo->{flake};
-my $flakeInfo = decode_json(`nix flake metadata --json "$flakeUrl"` or die);
+my $flakeInfo = decode_json(`nix flake metadata --json "$flakeUrl"` or die) if $flakeUrl;
-my $nixRev = $flakeInfo->{revision} or die;
+my $nixRev = ($flakeInfo ? $flakeInfo->{revision} : $evalInfo->{jobsetevalinputs}->{nix}->{revision}) or die;
 
 my $buildInfo = decode_json(fetch("$evalUrl/job/build.x86_64-linux", 'application/json'));
 #print Dumper($buildInfo);
@@ -83,12 +85,19 @@ my $channelsBucket = $s3_us->bucket($channelsBucketName) or die;
 sub getStorePath {
     my ($jobName, $output) = @_;
     my $buildInfo = decode_json(fetch("$evalUrl/job/$jobName", 'application/json'));
-    return $buildInfo->{buildoutputs}->{$output or "out"}->{path} or die "cannot get store path for '$jobName'";
+    return $buildInfo->{buildoutputs}->{$output or "out"}->{path} // die "cannot get store path for '$jobName'";
 }
 
 sub copyManual {
-    my $manual = getStorePath("build.x86_64-linux", "doc");
+    my $manual;
-    print "$manual\n";
+    eval {
+        $manual = getStorePath("build.x86_64-linux", "doc");
+    };
+    if ($@) {
+        warn "$@";
+        return;
+    }
+    print "Manual: $manual\n";
 
     my $manualNar = "$tmpDir/$releaseName-manual.nar.xz";
     print "$manualNar\n";
@@ -154,19 +163,33 @@ downloadFile("binaryTarball.x86_64-linux", "1");
 downloadFile("binaryTarball.aarch64-linux", "1");
 downloadFile("binaryTarball.x86_64-darwin", "1");
 downloadFile("binaryTarball.aarch64-darwin", "1");
-downloadFile("binaryTarballCross.x86_64-linux.armv6l-unknown-linux-gnueabihf", "1");
+eval {
-downloadFile("binaryTarballCross.x86_64-linux.armv7l-unknown-linux-gnueabihf", "1");
+    downloadFile("binaryTarballCross.x86_64-linux.armv6l-unknown-linux-gnueabihf", "1");
+};
+warn "$@" if $@;
+eval {
+    downloadFile("binaryTarballCross.x86_64-linux.armv7l-unknown-linux-gnueabihf", "1");
+};
+warn "$@" if $@;
 downloadFile("installerScript", "1");
 
 # Upload docker images to dockerhub.
 my $dockerManifest = "";
 my $dockerManifestLatest = "";
+my $haveDocker = 0;
 
 for my $platforms (["x86_64-linux", "amd64"], ["aarch64-linux", "arm64"]) {
     my $system = $platforms->[0];
     my $dockerPlatform = $platforms->[1];
     my $fn = "nix-$version-docker-image-$dockerPlatform.tar.gz";
-    downloadFile("dockerImage.$system", "1", $fn);
+    eval {
+        downloadFile("dockerImage.$system", "1", $fn);
+    };
+    if ($@) {
+        warn "$@" if $@;
+        next;
+    }
+    $haveDocker = 1;
 
     print STDERR "loading docker image for $dockerPlatform...\n";
     system("docker load -i $tmpDir/$fn") == 0 or die;
@@ -194,21 +217,23 @@ for my $platforms (["x86_64-linux", "amd64"], ["aarch64-linux", "arm64"]) {
     $dockerManifestLatest .= " --amend $latestTag"
 }
 
-print STDERR "creating multi-platform docker manifest...\n";
+if ($haveDocker) {
-system("docker manifest rm nixos/nix:$version");
+    print STDERR "creating multi-platform docker manifest...\n";
-system("docker manifest create nixos/nix:$version $dockerManifest") == 0 or die;
+    system("docker manifest rm nixos/nix:$version");
-if ($isLatest) {
+    system("docker manifest create nixos/nix:$version $dockerManifest") == 0 or die;
-    print STDERR "creating latest multi-platform docker manifest...\n";
+    if ($isLatest) {
-    system("docker manifest rm nixos/nix:latest");
+        print STDERR "creating latest multi-platform docker manifest...\n";
-    system("docker manifest create nixos/nix:latest $dockerManifestLatest") == 0 or die;
+        system("docker manifest rm nixos/nix:latest");
-}
+        system("docker manifest create nixos/nix:latest $dockerManifestLatest") == 0 or die;
+    }
 
-print STDERR "pushing multi-platform docker manifest...\n";
+    print STDERR "pushing multi-platform docker manifest...\n";
-system("docker manifest push nixos/nix:$version") == 0 or die;
+    system("docker manifest push nixos/nix:$version") == 0 or die;
 
-if ($isLatest) {
+    if ($isLatest) {
-    print STDERR "pushing latest multi-platform docker manifest...\n";
+        print STDERR "pushing latest multi-platform docker manifest...\n";
-    system("docker manifest push nixos/nix:latest") == 0 or die;
+        system("docker manifest push nixos/nix:latest") == 0 or die;
+    }
 }
 
 # Upload nix-fallback-paths.nix.

mk/cxx-big-literal.mk

@@ -1,5 +1,5 @@
 %.gen.hh: %
-	@echo 'R"foo(' >> $@.tmp
+	@echo 'R"__NIX_STR(' >> $@.tmp
 	$(trace-gen) cat $< >> $@.tmp
-	@echo ')foo"' >> $@.tmp
+	@echo ')__NIX_STR"' >> $@.tmp
 	@mv $@.tmp $@

package.nix

@@ -24,6 +24,7 @@
 , libgit2
 , libseccomp
 , libsodium
+, man
 , lowdown
 , mdbook
 , mdbook-linkcheck
@@ -213,6 +214,7 @@ in {
     git
     mercurial
     openssh
+    man # for testing `nix-* --help`
   ] ++ lib.optionals (doInstallCheck || enableManual) [
     jq # Also for custom mdBook preprocessor.
   ] ++ lib.optional stdenv.hostPlatform.isLinux util-linux
@@ -341,15 +343,22 @@ in {
 
   # Work around weird bug where it doesn't think there is a Makefile.
   installCheckPhase = if (!doBuild && doInstallCheck) then ''
+    runHook preInstallCheck
     mkdir -p src/nix-channel
     make installcheck -j$NIX_BUILD_CORES -l$NIX_BUILD_CORES
   '' else null;
 
   # Needed for tests if we are not doing a build, but testing existing
   # built Nix.
-  preInstallCheck = lib.optionalString (! doBuild) ''
+  preInstallCheck =
-    mkdir -p src/nix-channel
+    lib.optionalString (! doBuild) ''
-  '';
+      mkdir -p src/nix-channel
+    ''
+    # See https://github.com/NixOS/nix/issues/2523
+    # Occurs often in tests since https://github.com/NixOS/nix/pull/9900
+    + lib.optionalString stdenv.hostPlatform.isDarwin ''
+      export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
+    '';
 
   separateDebugInfo = !stdenv.hostPlatform.isStatic;
 

scripts/install-multi-user.sh

@@ -58,31 +58,6 @@ readonly EXTRACTED_NIX_PATH="$(dirname "$0")"
 
 readonly ROOT_HOME=~root
 
-readonly PROXY_ENVIRONMENT_VARIABLES=(
-    http_proxy
-    https_proxy
-    ftp_proxy
-    no_proxy
-    HTTP_PROXY
-    HTTPS_PROXY
-    FTP_PROXY
-    NO_PROXY
-)
-
-SUDO_EXTRA_ENVIRONMENT_VARIABLES=()
-
-setup_sudo_extra_environment_variables() {
-    local i=${#SUDO_EXTRA_ENVIRONMENT_VARIABLES[@]}
-    for variable in "${PROXY_ENVIRONMENT_VARIABLES[@]}"; do
-        if [ "x${!variable:-}" != "x" ]; then
-            SUDO_EXTRA_ENVIRONMENT_VARIABLES[i]="$variable=${!variable}"
-            i=$((i + 1))
-        fi
-    done
-}
-
-setup_sudo_extra_environment_variables
-
 if [ -t 0 ] && [ -z "${NIX_INSTALLER_YES:-}" ]; then
     readonly IS_HEADLESS='no'
 else
@@ -386,7 +361,7 @@ _sudo() {
     if is_root; then
         env "$@"
     else
-        sudo "${SUDO_EXTRA_ENVIRONMENT_VARIABLES[@]}" "$@"
+        sudo "$@"
     fi
 }
 

src/libcmd/common-eval-args.cc

@@ -20,7 +20,7 @@ MixEvalArgs::MixEvalArgs()
         .description = "Pass the value *expr* as the argument *name* to Nix functions.",
         .category = category,
         .labels = {"name", "expr"},
-        .handler = {[&](std::string name, std::string expr) { autoArgs[name] = 'E' + expr; }}
+        .handler = {[&](std::string name, std::string expr) { autoArgs.insert_or_assign(name, AutoArg{AutoArgExpr(expr)}); }}
     });
 
     addFlag({
@@ -28,7 +28,24 @@ MixEvalArgs::MixEvalArgs()
         .description = "Pass the string *string* as the argument *name* to Nix functions.",
         .category = category,
         .labels = {"name", "string"},
-        .handler = {[&](std::string name, std::string s) { autoArgs[name] = 'S' + s; }},
+        .handler = {[&](std::string name, std::string s) { autoArgs.insert_or_assign(name, AutoArg{AutoArgString(s)}); }},
+    });
+
+    addFlag({
+        .longName = "arg-from-file",
+        .description = "Pass the contents of file *path* as the argument *name* to Nix functions.",
+        .category = category,
+        .labels = {"name", "path"},
+        .handler = {[&](std::string name, std::string path) { autoArgs.insert_or_assign(name, AutoArg{AutoArgFile(path)}); }},
+        .completer = completePath
+    });
+
+    addFlag({
+        .longName = "arg-from-stdin",
+        .description = "Pass the contents of stdin as the argument *name* to Nix functions.",
+        .category = category,
+        .labels = {"name"},
+        .handler = {[&](std::string name) { autoArgs.insert_or_assign(name, AutoArg{AutoArgStdin{}}); }},
     });
 
     addFlag({
@@ -154,13 +171,23 @@ MixEvalArgs::MixEvalArgs()
 Bindings * MixEvalArgs::getAutoArgs(EvalState & state)
 {
     auto res = state.buildBindings(autoArgs.size());
-    for (auto & i : autoArgs) {
+    for (auto & [name, arg] : autoArgs) {
         auto v = state.allocValue();
-        if (i.second[0] == 'E')
+        std::visit(overloaded {
-            state.mkThunk_(*v, state.parseExprFromString(i.second.substr(1), state.rootPath(".")));
+            [&](const AutoArgExpr & arg) {
-        else
+                state.mkThunk_(*v, state.parseExprFromString(arg.expr, state.rootPath(".")));
-            v->mkString(((std::string_view) i.second).substr(1));
+            },
-        res.insert(state.symbols.create(i.first), v);
+            [&](const AutoArgString & arg) {
+                v->mkString(arg.s);
+            },
+            [&](const AutoArgFile & arg) {
+                v->mkString(readFile(arg.path));
+            },
+            [&](const AutoArgStdin & arg) {
+                v->mkString(readFile(STDIN_FILENO));
+            }
+        }, arg);
+        res.insert(state.symbols.create(name), v);
     }
     return res.finish();
 }

src/libcmd/common-eval-args.hh

@@ -6,6 +6,8 @@
 #include "common-args.hh"
 #include "search-path.hh"
 
+#include <filesystem>
+
 namespace nix {
 
 class Store;
@@ -26,7 +28,14 @@ struct MixEvalArgs : virtual Args, virtual MixRepair
     std::optional<std::string> evalStoreUrl;
 
 private:
-    std::map<std::string, std::string> autoArgs;
+    struct AutoArgExpr { std::string expr; };
+    struct AutoArgString { std::string s; };
+    struct AutoArgFile { std::filesystem::path path; };
+    struct AutoArgStdin { };
+
+    using AutoArg = std::variant<AutoArgExpr, AutoArgString, AutoArgFile, AutoArgStdin>;
+
+    std::map<std::string, AutoArg> autoArgs;
 };
 
 SourcePath lookupFileArg(EvalState & state, std::string_view s, const Path * baseDir = nullptr);

src/libcmd/installables.cc

@@ -21,6 +21,7 @@
 #include "url.hh"
 #include "registry.hh"
 #include "build-result.hh"
+#include "fs-input-accessor.hh"
 
 #include <regex>
 #include <queue>
@@ -146,7 +147,7 @@ MixFlakeOptions::MixFlakeOptions()
         .category = category,
         .labels = {"flake-lock-path"},
         .handler = {[&](std::string lockFilePath) {
-            lockFlags.referenceLockFilePath = lockFilePath;
+            lockFlags.referenceLockFilePath = getUnfilteredRootPath(CanonPath(absPath(lockFilePath)));
         }},
         .completer = completePath
     });
@@ -442,10 +443,10 @@ ref<eval_cache::EvalCache> openEvalCache(
     EvalState & state,
     std::shared_ptr<flake::LockedFlake> lockedFlake)
 {
-    auto fingerprint = lockedFlake->getFingerprint();
+    auto fingerprint = lockedFlake->getFingerprint(state.store);
     return make_ref<nix::eval_cache::EvalCache>(
         evalSettings.useEvalCache && evalSettings.pureEval
-            ? std::optional { std::cref(fingerprint) }
+            ? fingerprint
             : std::nullopt,
         state,
         [&state, lockedFlake]()

src/libcmd/repl.cc

@@ -123,7 +123,8 @@ struct NixRepl
             .force = true,
             .derivationPaths = true,
             .maxDepth = maxDepth,
-            .prettyIndent = 2
+            .prettyIndent = 2,
+            .errors = ErrorPrintBehavior::ThrowTopLevel,
         });
     }
 };
@@ -336,13 +337,7 @@ ReplExitStatus NixRepl::mainLoop()
               printMsg(lvlError, e.msg());
             }
         } catch (EvalError & e) {
-            // in debugger mode, an EvalError should trigger another repl session.
+            printMsg(lvlError, e.msg());
-            // when that session returns the exception will land here.  No need to show it again;
-            // show the error for this repl session instead.
-            if (state->debugRepl && !state->debugTraces.empty())
-                showDebugTrace(std::cout, state->positions, state->debugTraces.front());
-            else
-                printMsg(lvlError, e.msg());
         } catch (Error & e) {
             printMsg(lvlError, e.msg());
         } catch (Interrupted & e) {
@@ -548,6 +543,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
              << "  :l, :load <path>             Load Nix expression and add it to scope\n"
              << "  :lf, :load-flake <ref>       Load Nix flake and add it to scope\n"
              << "  :p, :print <expr>            Evaluate and print expression recursively\n"
+             << "                               Strings are printed directly, without escaping.\n"
              << "  :q, :quit                    Exit nix-repl\n"
              << "  :r, :reload                  Reload all files\n"
              << "  :sh <expr>                   Build dependencies of derivation, then start\n"
@@ -755,7 +751,11 @@ ProcessLineResult NixRepl::processLine(std::string line)
     else if (command == ":p" || command == ":print") {
         Value v;
         evalString(arg, v);
-        printValue(std::cout, v);
+        if (v.type() == nString) {
+            std::cout << v.string_view();
+        } else {
+            printValue(std::cout, v);
+        }
         std::cout << std::endl;
     }
 

src/libexpr/eval-settings.hh

@@ -21,11 +21,24 @@ struct EvalSettings : Config
     Setting<Strings> nixPath{
         this, getDefaultNixPath(), "nix-path",
         R"(
-          List of directories to be searched for `<...>` file references
+          List of search paths to use for [lookup path](@docroot@/language/constructs/lookup-path.md) resolution.
+          This setting determines the value of
+          [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath) and can be used with [`builtins.findFile`](@docroot@/language/builtin-constants.md#builtins-findFile).
 
-          In particular, outside of [pure evaluation mode](#conf-pure-eval), this determines the value of
+          The default value is
-          [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath).
+
-        )"};
+          ```
+          $HOME/.nix-defexpr/channels
+          nixpkgs=$NIX_STATE_DIR/profiles/per-user/root/channels/nixpkgs
+          $NIX_STATE_DIR/profiles/per-user/root/channels
+          ```
+
+          It can be overridden with the [`NIX_PATH` environment variable](@docroot@/command-ref/env-common.md#env-NIX_PATH) or the [`-I` command line option](@docroot@/command-ref/opt-common.md#opt-I).
+
+          > **Note**
+          >
+          > If [pure evaluation](#conf-pure-eval) is enabled, `nixPath` evaluates to the empty list `[ ]`.
+        )", {}, false};
 
     Setting<std::string> currentSystem{
         this, "", "eval-system",
@@ -55,8 +68,6 @@ struct EvalSettings : Config
           [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath),
           or to URIs outside of
           [`allowed-uris`](@docroot@/command-ref/conf-file.md#conf-allowed-uris).
-
-          Also the default value for [`nix-path`](#conf-nix-path) is ignored, such that only explicitly set search path entries are taken into account.
         )"};
 
     Setting<bool> pureEval{this, false, "pure-eval",

src/libexpr/eval.cc

@@ -762,10 +762,24 @@ std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const Stati
     return vm;
 }
 
+/**
+ * Sets `inDebugger` to true on construction and false on destruction.
+ */
+class DebuggerGuard {
+    bool & inDebugger;
+public:
+    DebuggerGuard(bool & inDebugger) : inDebugger(inDebugger) {
+        inDebugger = true;
+    }
+    ~DebuggerGuard() {
+        inDebugger = false;
+    }
+};
+
 void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr & expr)
 {
-    // double check we've got the debugRepl function pointer.
+    // Make sure we have a debugger to run and we're not already in a debugger.
-    if (!debugRepl)
+    if (!debugRepl || inDebugger)
         return;
 
     auto dts =
@@ -792,6 +806,7 @@ void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr &
     auto se = getStaticEnv(expr);
     if (se) {
         auto vm = mapStaticEnvBindings(symbols, *se.get(), env);
+        DebuggerGuard _guard(inDebugger);
         auto exitStatus = (debugRepl)(ref<EvalState>(shared_from_this()), *vm);
         switch (exitStatus) {
             case ReplExitStatus::QuitAll:
@@ -934,12 +949,11 @@ void EvalState::mkThunk_(Value & v, Expr * expr)
 
 void EvalState::mkPos(Value & v, PosIdx p)
 {
-    auto pos = positions[p];
+    auto origin = positions.originOf(p);
-    if (auto path = std::get_if<SourcePath>(&pos.origin)) {
+    if (auto path = std::get_if<SourcePath>(&origin)) {
         auto attrs = buildBindings(3);
         attrs.alloc(sFile).mkString(path->path.abs());
-        attrs.alloc(sLine).mkInt(pos.line);
+        makePositionThunks(*this, p, attrs.alloc(sLine), attrs.alloc(sColumn));
-        attrs.alloc(sColumn).mkInt(pos.column);
         v.mkAttrs(attrs);
     } else
         v.mkNull();
@@ -2762,9 +2776,12 @@ Expr * EvalState::parseExprFromFile(const SourcePath & path, std::shared_ptr<Sta
 
 Expr * EvalState::parseExprFromString(std::string s_, const SourcePath & basePath, std::shared_ptr<StaticEnv> & staticEnv)
 {
-    auto s = make_ref<std::string>(std::move(s_));
+    // NOTE this method (and parseStdin) must take care to *fully copy* their input
-    s->append("\0\0", 2);
+    // into their respective Pos::Origin until the parser stops overwriting its input
-    return parse(s->data(), s->size(), Pos::String{.source = s}, basePath, staticEnv);
+    // data.
+    auto s = make_ref<std::string>(s_);
+    s_.append("\0\0", 2);
+    return parse(s_.data(), s_.size(), Pos::String{.source = s}, basePath, staticEnv);
 }
 
 
@@ -2776,12 +2793,15 @@ Expr * EvalState::parseExprFromString(std::string s, const SourcePath & basePath
 
 Expr * EvalState::parseStdin()
 {
+    // NOTE this method (and parseExprFromString) must take care to *fully copy* their
+    // input into their respective Pos::Origin until the parser stops overwriting its
+    // input data.
     //Activity act(*logger, lvlTalkative, "parsing standard input");
     auto buffer = drainFD(0);
     // drainFD should have left some extra space for terminators
     buffer.append("\0\0", 2);
-    auto s = make_ref<std::string>(std::move(buffer));
+    auto s = make_ref<std::string>(buffer);
-    return parse(s->data(), s->size(), Pos::Stdin{.source = s}, rootPath("."), staticBaseEnv);
+    return parse(buffer.data(), buffer.size(), Pos::Stdin{.source = s}, rootPath("."), staticBaseEnv);
 }
 
 

src/libexpr/eval.hh

@@ -153,6 +153,7 @@ struct DebugTrace {
     bool isError;
 };
 
+
 class EvalState : public std::enable_shared_from_this<EvalState>
 {
 public:
@@ -222,6 +223,7 @@ public:
      */
     ReplExitStatus (* debugRepl)(ref<EvalState> es, const ValMap & extraEnv);
     bool debugStop;
+    bool inDebugger = false;
     int trylevel;
     std::list<DebugTrace> debugTraces;
     std::map<const Expr*, const std::shared_ptr<const StaticEnv>> exprEnvs;

src/libexpr/flake/flake.cc

@@ -139,7 +139,7 @@ static FlakeInput parseFlakeInput(EvalState & state,
                         attrs.emplace(state.symbols[attr.name], Explicit<bool> { attr.value->boolean });
                         break;
                     case nInt:
-                        attrs.emplace(state.symbols[attr.name], (long unsigned int)attr.value->integer);
+                        attrs.emplace(state.symbols[attr.name], (long unsigned int) attr.value->integer);
                         break;
                     default:
                         if (attr.name == state.symbols.create("publicKeys")) {
@@ -202,43 +202,27 @@ static std::map<FlakeId, FlakeInput> parseFlakeInputs(
     return inputs;
 }
 
-static Flake getFlake(
+static Flake readFlake(
     EvalState & state,
     const FlakeRef & originalRef,
-    bool allowLookup,
+    const FlakeRef & resolvedRef,
-    FlakeCache & flakeCache,
+    const FlakeRef & lockedRef,
-    InputPath lockRootPath)
+    const SourcePath & rootDir,
+    const InputPath & lockRootPath)
 {
-    auto [storePath, resolvedRef, lockedRef] = fetchOrSubstituteTree(
+    auto flakePath = rootDir / CanonPath(resolvedRef.subdir) / "flake.nix";
-        state, originalRef, allowLookup, flakeCache);
 
-    // We need to guard against symlink attacks, but before we start doing
+    // NOTE evalFile forces vInfo to be an attrset because mustBeTrivial is true.
-    // filesystem operations we should make sure there's a flake.nix in the
+    Value vInfo;
-    // first place.
+    state.evalFile(flakePath, vInfo, true);
-    auto unsafeFlakeDir = state.store->toRealPath(storePath) + "/" + lockedRef.subdir;
-    auto unsafeFlakeFile = unsafeFlakeDir + "/flake.nix";
-    if (!pathExists(unsafeFlakeFile))
-        throw Error("source tree referenced by '%s' does not contain a '%s/flake.nix' file", lockedRef, lockedRef.subdir);
-
-    // Guard against symlink attacks.
-    auto flakeDir = canonPath(unsafeFlakeDir, true);
-    auto flakeFile = canonPath(flakeDir + "/flake.nix", true);
-    if (!isInDir(flakeFile, state.store->toRealPath(storePath)))
-        throw Error("'flake.nix' file of flake '%s' escapes from '%s'",
-            lockedRef, state.store->printStorePath(storePath));
 
     Flake flake {
         .originalRef = originalRef,
         .resolvedRef = resolvedRef,
         .lockedRef = lockedRef,
-        .storePath = storePath,
+        .path = flakePath,
     };
 
-    Value vInfo;
-    state.evalFile(state.rootPath(CanonPath(flakeFile)), vInfo, true); // FIXME: symlink attack
-
-    expectType(state, nAttrs, vInfo, state.positions.add({state.rootPath(CanonPath(flakeFile))}, 1, 1));
-
     if (auto description = vInfo.attrs->get(state.sDescription)) {
         expectType(state, nString, *description->value, description->pos);
         flake.description = description->value->c_str();
@@ -247,7 +231,7 @@ static Flake getFlake(
     auto sInputs = state.symbols.create("inputs");
 
     if (auto inputs = vInfo.attrs->get(sInputs))
-        flake.inputs = parseFlakeInputs(state, inputs->value, inputs->pos, flakeDir, lockRootPath);
+        flake.inputs = parseFlakeInputs(state, inputs->value, inputs->pos, flakePath.parent().path.abs(), lockRootPath); // FIXME
 
     auto sOutputs = state.symbols.create("outputs");
 
@@ -264,7 +248,7 @@ static Flake getFlake(
         }
 
     } else
-        throw Error("flake '%s' lacks attribute 'outputs'", lockedRef);
+        throw Error("flake '%s' lacks attribute 'outputs'", resolvedRef);
 
     auto sNixConfig = state.symbols.create("nixConfig");
 
@@ -281,7 +265,7 @@ static Flake getFlake(
                 NixStringContext emptyContext = {};
                 flake.config.settings.emplace(
                     state.symbols[setting.name],
-                    state.coerceToString(setting.pos, *setting.value, emptyContext, "", false, true, true) .toOwned());
+                    state.coerceToString(setting.pos, *setting.value, emptyContext, "", false, true, true).toOwned());
             }
             else if (setting.value->type() == nInt)
                 flake.config.settings.emplace(
@@ -313,12 +297,25 @@ static Flake getFlake(
             attr.name != sOutputs &&
             attr.name != sNixConfig)
             throw Error("flake '%s' has an unsupported attribute '%s', at %s",
-                lockedRef, state.symbols[attr.name], state.positions[attr.pos]);
+                resolvedRef, state.symbols[attr.name], state.positions[attr.pos]);
     }
 
     return flake;
 }
 
+static Flake getFlake(
+    EvalState & state,
+    const FlakeRef & originalRef,
+    bool allowLookup,
+    FlakeCache & flakeCache,
+    InputPath lockRootPath)
+{
+    auto [storePath, resolvedRef, lockedRef] = fetchOrSubstituteTree(
+        state, originalRef, allowLookup, flakeCache);
+
+    return readFlake(state, originalRef, resolvedRef, lockedRef, state.rootPath(state.store->toRealPath(storePath)), lockRootPath);
+}
+
 Flake getFlake(EvalState & state, const FlakeRef & originalRef, bool allowLookup, FlakeCache & flakeCache)
 {
     return getFlake(state, originalRef, allowLookup, flakeCache, {});
@@ -330,6 +327,13 @@ Flake getFlake(EvalState & state, const FlakeRef & originalRef, bool allowLookup
     return getFlake(state, originalRef, allowLookup, flakeCache);
 }
 
+static LockFile readLockFile(const SourcePath & lockFilePath)
+{
+    return lockFilePath.pathExists()
+        ? LockFile(lockFilePath.readFile(), fmt("%s", lockFilePath))
+        : LockFile();
+}
+
 /* Compute an in-memory lock file for the specified top-level flake,
    and optionally write it to file, if the flake is writable. */
 LockedFlake lockFlake(
@@ -355,17 +359,16 @@ LockedFlake lockFlake(
             throw Error("reference lock file was provided, but the `allow-dirty` setting is set to false");
         }
 
-        // FIXME: symlink attack
+        auto oldLockFile = readLockFile(
-        auto oldLockFile = LockFile::read(
             lockFlags.referenceLockFilePath.value_or(
-                state.store->toRealPath(flake.storePath) + "/" + flake.lockedRef.subdir + "/flake.lock"));
+                flake.lockFilePath()));
 
         debug("old lock file: %s", oldLockFile);
 
         std::map<InputPath, FlakeInput> overrides;
         std::set<InputPath> explicitCliOverrides;
         std::set<InputPath> overridesUsed, updatesUsed;
-        std::map<ref<Node>, StorePath> nodePaths;
+        std::map<ref<Node>, SourcePath> nodePaths;
 
         for (auto & i : lockFlags.inputOverrides) {
             overrides.insert_or_assign(i.first, FlakeInput { .ref = i.second });
@@ -538,7 +541,7 @@ LockedFlake lockFlake(
 
                         if (mustRefetch) {
                             auto inputFlake = getFlake(state, oldLock->lockedRef, false, flakeCache, inputPath);
-                            nodePaths.emplace(childNode, inputFlake.storePath);
+                            nodePaths.emplace(childNode, inputFlake.path.parent());
                             computeLocks(inputFlake.inputs, childNode, inputPath, oldLock, lockRootPath, parentPath, false);
                         } else {
                             computeLocks(fakeInputs, childNode, inputPath, oldLock, lockRootPath, parentPath, true);
@@ -587,13 +590,12 @@ LockedFlake lockFlake(
                                flake. Also, unless we already have this flake
                                in the top-level lock file, use this flake's
                                own lock file. */
-                            nodePaths.emplace(childNode, inputFlake.storePath);
+                            nodePaths.emplace(childNode, inputFlake.path.parent());
                             computeLocks(
                                 inputFlake.inputs, childNode, inputPath,
                                 oldLock
                                 ? std::dynamic_pointer_cast<const Node>(oldLock)
-                                : LockFile::read(
+                                : readLockFile(inputFlake.lockFilePath()).root.get_ptr(),
-                                    state.store->toRealPath(inputFlake.storePath) + "/" + inputFlake.lockedRef.subdir + "/flake.lock").root.get_ptr(),
                                 oldLock ? lockRootPath : inputPath,
                                 localPath,
                                 false);
@@ -605,7 +607,7 @@ LockedFlake lockFlake(
 
                             auto childNode = make_ref<LockedNode>(lockedRef, ref, false);
 
-                            nodePaths.emplace(childNode, storePath);
+                            nodePaths.emplace(childNode, state.rootPath(state.store->toRealPath(storePath)));
 
                             node->inputs.insert_or_assign(id, childNode);
                         }
@@ -619,9 +621,9 @@ LockedFlake lockFlake(
         };
 
         // Bring in the current ref for relative path resolution if we have it
-        auto parentPath = canonPath(state.store->toRealPath(flake.storePath) + "/" + flake.lockedRef.subdir, true);
+        auto parentPath = flake.path.parent().path.abs();
 
-        nodePaths.emplace(newLockFile.root, flake.storePath);
+        nodePaths.emplace(newLockFile.root, flake.path.parent());
 
         computeLocks(
             flake.inputs,
@@ -746,13 +748,15 @@ void callFlake(EvalState & state,
 
     auto overrides = state.buildBindings(lockedFlake.nodePaths.size());
 
-    for (auto & [node, storePath] : lockedFlake.nodePaths) {
+    for (auto & [node, sourcePath] : lockedFlake.nodePaths) {
         auto override = state.buildBindings(2);
 
         auto & vSourceInfo = override.alloc(state.symbols.create("sourceInfo"));
 
         auto lockedNode = node.dynamic_pointer_cast<const LockedNode>();
 
+        auto [storePath, subdir] = state.store->toStorePath(sourcePath.path.abs());
+
         emitTreeAttrs(
             state,
             storePath,
@@ -766,7 +770,7 @@ void callFlake(EvalState & state,
 
         override
             .alloc(state.symbols.create("dir"))
-            .mkString(lockedNode ? lockedNode->lockedRef.subdir : lockedFlake.flake.lockedRef.subdir);
+            .mkString(CanonPath(subdir).rel());
 
         overrides.alloc(state.symbols.create(key->second)).mkAttrs(override);
     }
@@ -921,18 +925,17 @@ static RegisterPrimOp r4({
 
 }
 
-Fingerprint LockedFlake::getFingerprint() const
+std::optional<Fingerprint> LockedFlake::getFingerprint(ref<Store> store) const
 {
+    if (lockFile.isUnlocked()) return std::nullopt;
+
+    auto fingerprint = flake.lockedRef.input.getFingerprint(store);
+    if (!fingerprint) return std::nullopt;
+
     // FIXME: as an optimization, if the flake contains a lock file
     // and we haven't changed it, then it's sufficient to use
     // flake.sourceInfo.storePath for the fingerprint.
-    return hashString(HashAlgorithm::SHA256,
+    return hashString(HashAlgorithm::SHA256, fmt("%s;%s;%s", *fingerprint, flake.lockedRef.subdir, lockFile));
-        fmt("%s;%s;%d;%d;%s",
-            flake.storePath.to_string(),
-            flake.lockedRef.subdir,
-            flake.lockedRef.input.getRevCount().value_or(0),
-            flake.lockedRef.input.getLastModified().value_or(0),
-            lockFile));
 }
 
 Flake::~Flake() { }

src/libexpr/flake/flake.hh

@@ -77,18 +77,27 @@ struct Flake
      * the specific local store result of invoking the fetcher
      */
     FlakeRef lockedRef;
+    /**
+     * The path of `flake.nix`.
+     */
+    SourcePath path;
     /**
      * pretend that 'lockedRef' is dirty
      */
     bool forceDirty = false;
     std::optional<std::string> description;
-    StorePath storePath;
     FlakeInputs inputs;
     /**
      * 'nixConfig' attribute
      */
     ConfigFile config;
+
     ~Flake();
+
+    SourcePath lockFilePath()
+    {
+        return path.parent() / "flake.lock";
+    }
 };
 
 Flake getFlake(EvalState & state, const FlakeRef & flakeRef, bool allowLookup);
@@ -104,13 +113,13 @@ struct LockedFlake
     LockFile lockFile;
 
     /**
-     * Store paths of nodes that have been fetched in
+     * Source tree accessors for nodes that have been fetched in
      * lockFlake(); in particular, the root node and the overriden
      * inputs.
      */
-    std::map<ref<Node>, StorePath> nodePaths;
+    std::map<ref<Node>, SourcePath> nodePaths;
 
-    Fingerprint getFingerprint() const;
+    std::optional<Fingerprint> getFingerprint(ref<Store> store) const;
 };
 
 struct LockFlags
@@ -165,7 +174,7 @@ struct LockFlags
     /**
      * The path to a lock file to read instead of the `flake.lock` file in the top-level flake
      */
-    std::optional<std::string> referenceLockFilePath;
+    std::optional<SourcePath> referenceLockFilePath;
 
     /**
      * The path to a lock file to write to instead of the `flake.lock` file in the top-level flake

src/libexpr/flake/flakeref.cc

@@ -102,6 +102,19 @@ std::pair<FlakeRef, std::string> parsePathFlakeRefWithFragment(
 
         if (isFlake) {
 
+            if (!S_ISDIR(lstat(path).st_mode)) {
+                if (baseNameOf(path) == "flake.nix") {
+                    // Be gentle with people who accidentally write `/foo/bar/flake.nix` instead of `/foo/bar`
+                    warn(
+                        "Path '%s' should point at the directory containing the 'flake.nix' file, not the file itself. "
+                        "Pretending that you meant '%s'"
+                        , path, dirOf(path));
+                    path = dirOf(path);
+                } else {
+                    throw BadURL("path '%s' is not a flake (because it's not a directory)", path);
+                }
+            }
+
             if (!allowMissing && !pathExists(path + "/flake.nix")){
                 notice("path '%s' does not contain a 'flake.nix', searching up",path);
 
@@ -124,9 +137,6 @@ std::pair<FlakeRef, std::string> parsePathFlakeRefWithFragment(
                     throw BadURL("could not find a flake.nix file");
             }
 
-            if (!S_ISDIR(lstat(path).st_mode))
-                throw BadURL("path '%s' is not a flake (because it's not a directory)", path);
-
             if (!allowMissing && !pathExists(path + "/flake.nix"))
                 throw BadURL("path '%s' is not a flake (because it doesn't contain a 'flake.nix' file)", path);
 
@@ -274,7 +284,7 @@ FlakeRef FlakeRef::fromAttrs(const fetchers::Attrs & attrs)
 
 std::pair<StorePath, FlakeRef> FlakeRef::fetchTree(ref<Store> store) const
 {
-    auto [storePath, lockedInput] = input.fetch(store);
+    auto [storePath, lockedInput] = input.fetchToStore(store);
     return {std::move(storePath), FlakeRef(std::move(lockedInput), subdir)};
 }
 

src/libexpr/flake/lockfile.cc

@@ -84,8 +84,10 @@ std::shared_ptr<Node> LockFile::findInput(const InputPath & path)
     return doFind(root, path, visited);
 }
 
-LockFile::LockFile(const nlohmann::json & json, const Path & path)
+LockFile::LockFile(std::string_view contents, std::string_view path)
 {
+    auto json = nlohmann::json::parse(contents);
+
     auto version = json.value("version", 0);
     if (version < 5 || version > 7)
         throw Error("lock file '%s' has unsupported version %d", path, version);
@@ -203,12 +205,6 @@ std::pair<std::string, LockFile::KeyMap> LockFile::to_string() const
     return {json.dump(2), std::move(nodeKeys)};
 }
 
-LockFile LockFile::read(const Path & path)
-{
-    if (!pathExists(path)) return LockFile();
-    return LockFile(nlohmann::json::parse(readFile(path)), path);
-}
-
 std::ostream & operator <<(std::ostream & stream, const LockFile & lockFile)
 {
     stream << lockFile.toJSON().first.dump(2);

src/libexpr/flake/lockfile.hh

@@ -55,7 +55,7 @@ struct LockFile
     ref<Node> root = make_ref<Node>();
 
     LockFile() {};
-    LockFile(const nlohmann::json & json, const Path & path);
+    LockFile(std::string_view contents, std::string_view path);
 
     typedef std::map<ref<const Node>, std::string> KeyMap;
 
@@ -63,8 +63,6 @@ struct LockFile
 
     std::pair<std::string, KeyMap> to_string() const;
 
-    static LockFile read(const Path & path);
-
     /**
      * Check whether this lock file has any unlocked inputs. If so,
      * return one.

src/libexpr/lexer.l

@@ -33,33 +33,16 @@ namespace nix {
 
 static void initLoc(YYLTYPE * loc)
 {
-    loc->first_line = loc->last_line = 1;
+    loc->first_line = loc->last_line = 0;
-    loc->first_column = loc->last_column = 1;
+    loc->first_column = loc->last_column = 0;
 }
 
 static void adjustLoc(YYLTYPE * loc, const char * s, size_t len)
 {
     loc->stash();
 
-    loc->first_line = loc->last_line;
     loc->first_column = loc->last_column;
-
+    loc->last_column += len;
-    for (size_t i = 0; i < len; i++) {
-       switch (*s++) {
-       case '\r':
-           if (*s == '\n') { /* cr/lf */
-               i++;
-               s++;
-           }
-           /* fall through */
-       case '\n':
-           ++loc->last_line;
-           loc->last_column = 1;
-           break;
-       default:
-           ++loc->last_column;
-       }
-    }
 }
 
 

src/libexpr/nixexpr.cc

@@ -149,7 +149,10 @@ void ExprLambda::show(const SymbolTable & symbols, std::ostream & str) const
     if (hasFormals()) {
         str << "{ ";
         bool first = true;
-        for (auto & i : formals->formals) {
+        // the natural Symbol ordering is by creation time, which can lead to the
+        // same expression being printed in two different ways depending on its
+        // context. always use lexicographic ordering to avoid this.
+        for (auto & i : formals->lexicographicOrder(symbols)) {
             if (first) first = false; else str << ", ";
             str << symbols[i.name];
             if (i.def) {
@@ -580,6 +583,39 @@ std::string ExprLambda::showNamePos(const EvalState & state) const
 
 
 
+/* Position table. */
+
+Pos PosTable::operator[](PosIdx p) const
+{
+    auto origin = resolve(p);
+    if (!origin)
+        return {};
+
+    const auto offset = origin->offsetOf(p);
+
+    Pos result{0, 0, origin->origin};
+    auto lines = this->lines.lock();
+    auto linesForInput = (*lines)[origin->offset];
+
+    if (linesForInput.empty()) {
+        auto source = result.getSource().value_or("");
+        const char * begin = source.data();
+        for (Pos::LinesIterator it(source), end; it != end; it++)
+            linesForInput.push_back(it->data() - begin);
+        if (linesForInput.empty())
+            linesForInput.push_back(0);
+    }
+    // as above: the first line starts at byte 0 and is always present
+    auto lineStartOffset = std::prev(
+        std::upper_bound(linesForInput.begin(), linesForInput.end(), offset));
+
+    result.line = 1 + (lineStartOffset - linesForInput.begin());
+    result.column = 1 + (offset - *lineStartOffset);
+    return result;
+}
+
+
+
 /* Symbol table. */
 
 size_t SymbolTable::totalSize() const

src/libexpr/nixexpr.hh

@@ -7,7 +7,6 @@
 #include "value.hh"
 #include "symbol-table.hh"
 #include "error.hh"
-#include "chunked-vector.hh"
 #include "position.hh"
 #include "eval-error.hh"
 #include "pos-idx.hh"

src/libexpr/parser-state.hh

@@ -24,20 +24,15 @@ struct ParserLocation
     int last_line, last_column;
 
     // backup to recover from yyless(0)
-    int stashed_first_line, stashed_first_column;
+    int stashed_first_column, stashed_last_column;
-    int stashed_last_line, stashed_last_column;
 
     void stash() {
-        stashed_first_line = first_line;
         stashed_first_column = first_column;
-        stashed_last_line = last_line;
         stashed_last_column = last_column;
     }
 
     void unstash() {
-        first_line = stashed_first_line;
         first_column = stashed_first_column;
-        last_line = stashed_last_line;
         last_column = stashed_last_column;
     }
 };
@@ -276,7 +271,7 @@ inline Expr * ParserState::stripIndentation(const PosIdx pos,
 
 inline PosIdx ParserState::at(const ParserLocation & loc)
 {
-    return positions.add(origin, loc.first_line, loc.first_column);
+    return positions.add(origin, loc.first_column);
 }
 
 }

src/libexpr/parser.y

@@ -64,6 +64,10 @@ using namespace nix;
 
 void yyerror(YYLTYPE * loc, yyscan_t scanner, ParserState * state, const char * error)
 {
+    if (std::string_view(error).starts_with("syntax error, unexpected end of file")) {
+        loc->first_column = loc->last_column;
+        loc->first_line = loc->last_line;
+    }
     throw ParseError({
         .msg = HintFmt(error),
         .pos = state->positions[state->at(*loc)]
@@ -87,6 +91,7 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParserState * state, const char *
   nix::StringToken uri;
   nix::StringToken str;
   std::vector<nix::AttrName> * attrNames;
+  std::vector<std::pair<nix::AttrName, nix::PosIdx>> * inheritAttrs;
   std::vector<std::pair<nix::PosIdx, nix::Expr *>> * string_parts;
   std::vector<std::pair<nix::PosIdx, std::variant<nix::Expr *, nix::StringToken>>> * ind_string_parts;
 }
@@ -97,7 +102,8 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParserState * state, const char *
 %type <attrs> binds
 %type <formals> formals
 %type <formal> formal
-%type <attrNames> attrs attrpath
+%type <attrNames> attrpath
+%type <inheritAttrs> attrs
 %type <string_parts> string_parts_interpolated
 %type <ind_string_parts> ind_string_parts
 %type <e> path_start string_parts string_attr
@@ -309,13 +315,12 @@ binds
   : binds attrpath '=' expr ';' { $$ = $1; state->addAttr($$, std::move(*$2), $4, state->at(@2)); delete $2; }
   | binds INHERIT attrs ';'
     { $$ = $1;
-      for (auto & i : *$3) {
+      for (auto & [i, iPos] : *$3) {
           if ($$->attrs.find(i.symbol) != $$->attrs.end())
-              state->dupAttr(i.symbol, state->at(@3), $$->attrs[i.symbol].pos);
+              state->dupAttr(i.symbol, iPos, $$->attrs[i.symbol].pos);
-          auto pos = state->at(@3);
           $$->attrs.emplace(
               i.symbol,
-              ExprAttrs::AttrDef(new ExprVar(CUR_POS, i.symbol), pos, ExprAttrs::AttrDef::Kind::Inherited));
+              ExprAttrs::AttrDef(new ExprVar(iPos, i.symbol), iPos, ExprAttrs::AttrDef::Kind::Inherited));
       }
       delete $3;
     }
@@ -325,14 +330,14 @@ binds
           $$->inheritFromExprs = std::make_unique<std::vector<Expr *>>();
       $$->inheritFromExprs->push_back($4);
       auto from = new nix::ExprInheritFrom(state->at(@4), $$->inheritFromExprs->size() - 1);
-      for (auto & i : *$6) {
+      for (auto & [i, iPos] : *$6) {
           if ($$->attrs.find(i.symbol) != $$->attrs.end())
-              state->dupAttr(i.symbol, state->at(@6), $$->attrs[i.symbol].pos);
+              state->dupAttr(i.symbol, iPos, $$->attrs[i.symbol].pos);
           $$->attrs.emplace(
               i.symbol,
               ExprAttrs::AttrDef(
-                  new ExprSelect(CUR_POS, from, i.symbol),
+                  new ExprSelect(iPos, from, i.symbol),
-                  state->at(@6),
+                  iPos,
                   ExprAttrs::AttrDef::Kind::InheritedFrom));
       }
       delete $6;
@@ -341,12 +346,12 @@ binds
   ;
 
 attrs
-  : attrs attr { $$ = $1; $1->push_back(AttrName(state->symbols.create($2))); }
+  : attrs attr { $$ = $1; $1->emplace_back(AttrName(state->symbols.create($2)), state->at(@2)); }
   | attrs string_attr
     { $$ = $1;
       ExprString * str = dynamic_cast<ExprString *>($2);
       if (str) {
-          $$->push_back(AttrName(state->symbols.create(str->s)));
+          $$->emplace_back(AttrName(state->symbols.create(str->s)), state->at(@2));
           delete str;
       } else
           throw ParseError({
@@ -354,7 +359,7 @@ attrs
               .pos = state->positions[state->at(@2)]
           });
     }
-  | { $$ = new AttrPath; }
+  | { $$ = new std::vector<std::pair<AttrName, PosIdx>>; }
   ;
 
 attrpath
@@ -433,7 +438,7 @@ Expr * parseExprFromBuf(
         .symbols = symbols,
         .positions = positions,
         .basePath = basePath,
-        .origin = {origin},
+        .origin = positions.addOrigin(origin, length),
         .rootFS = rootFS,
         .s = astSymbols,
     };

src/libexpr/pos-idx.hh

@@ -6,6 +6,7 @@ namespace nix {
 
 class PosIdx
 {
+    friend struct LazyPosAcessors;
     friend class PosTable;
 
 private:

src/libexpr/pos-table.hh

@@ -7,6 +7,7 @@
 #include "chunked-vector.hh"
 #include "pos-idx.hh"
 #include "position.hh"
+#include "sync.hh"
 
 namespace nix {
 
@@ -17,66 +18,69 @@ public:
     {
         friend PosTable;
     private:
-        // must always be invalid by default, add() replaces this with the actual value.
+        uint32_t offset;
-        // subsequent add() calls use this index as a token to quickly check whether the
-        // current origins.back() can be reused or not.
-        mutable uint32_t idx = std::numeric_limits<uint32_t>::max();
 
-        // Used for searching in PosTable::[].
+        Origin(Pos::Origin origin, uint32_t offset, size_t size):
-        explicit Origin(uint32_t idx)
+            offset(offset), origin(origin), size(size)
-            : idx(idx)
+        {}
-            , origin{std::monostate()}
-        {
-        }
 
     public:
         const Pos::Origin origin;
+        const size_t size;
 
-        Origin(Pos::Origin origin)
+        uint32_t offsetOf(PosIdx p) const
-            : origin(origin)
         {
+            return p.id - 1 - offset;
         }
     };
 
-    struct Offset
-    {
-        uint32_t line, column;
-    };
-
 private:
-    std::vector<Origin> origins;
+    using Lines = std::vector<uint32_t>;
-    ChunkedVector<Offset, 8192> offsets;
 
-public:
+    std::map<uint32_t, Origin> origins;
-    PosTable()
+    mutable Sync<std::map<uint32_t, Lines>> lines;
-        : offsets(1024)
-    {
-        origins.reserve(1024);
-    }
 
-    PosIdx add(const Origin & origin, uint32_t line, uint32_t column)
+    const Origin * resolve(PosIdx p) const
     {
-        const auto idx = offsets.add({line, column}).second;
+        if (p.id == 0)
-        if (origins.empty() || origins.back().idx != origin.idx) {
+            return nullptr;
-            origin.idx = idx;
-            origins.push_back(origin);
-        }
-        return PosIdx(idx + 1);
-    }
 
-    Pos operator[](PosIdx p) const
-    {
-        if (p.id == 0 || p.id > offsets.size())
-            return {};
         const auto idx = p.id - 1;
         /* we want the last key <= idx, so we'll take prev(first key > idx).
-           this is guaranteed to never rewind origin.begin because the first
+            this is guaranteed to never rewind origin.begin because the first
-           key is always 0. */
+            key is always 0. */
-        const auto pastOrigin = std::upper_bound(
+        const auto pastOrigin = origins.upper_bound(idx);
-            origins.begin(), origins.end(), Origin(idx), [](const auto & a, const auto & b) { return a.idx < b.idx; });
+        return &std::prev(pastOrigin)->second;
-        const auto origin = *std::prev(pastOrigin);
+    }
-        const auto offset = offsets[idx];
+
-        return {offset.line, offset.column, origin.origin};
+public:
+    Origin addOrigin(Pos::Origin origin, size_t size)
+    {
+        uint32_t offset = 0;
+        if (auto it = origins.rbegin(); it != origins.rend())
+            offset = it->first + it->second.size;
+        // +1 because all PosIdx are offset by 1 to begin with, and
+        // another +1 to ensure that all origins can point to EOF, eg
+        // on (invalid) empty inputs.
+        if (2 + offset + size < offset)
+            return Origin{origin, offset, 0};
+        return origins.emplace(offset, Origin{origin, offset, size}).first->second;
+    }
+
+    PosIdx add(const Origin & origin, size_t offset)
+    {
+        if (offset > origin.size)
+            return PosIdx();
+        return PosIdx(1 + origin.offset + offset);
+    }
+
+    Pos operator[](PosIdx p) const;
+
+    Pos::Origin originOf(PosIdx p) const
+    {
+        if (auto o = resolve(p))
+            return o->origin;
+        return std::monostate{};
     }
 };
 

src/libexpr/primops.cc

@@ -1736,7 +1736,7 @@ static RegisterPrimOp primop_findFile(PrimOp {
       - If the suffix is found inside that directory, then the entry is a match.
         The combined absolute path of the directory (now downloaded if need be) and the suffix is returned.
 
-      [Lookup path](@docroot@/language/constructs/lookup-path.md) expressions can be [desugared](https://en.wikipedia.org/wiki/Syntactic_sugar) using this and [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath):
+      [Lookup path](@docroot@/language/constructs/lookup-path.md) expressions are [desugared](https://en.wikipedia.org/wiki/Syntactic_sugar) using this and [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath):
 
       ```nix
       <nixpkgs>
@@ -2524,6 +2524,54 @@ static RegisterPrimOp primop_unsafeGetAttrPos(PrimOp {
     .fun = prim_unsafeGetAttrPos,
 });
 
+// access to exact position information (ie, line and colum numbers) is deferred
+// due to the cost associated with calculating that information and how rarely
+// it is used in practice. this is achieved by creating thunks to otherwise
+// inaccessible primops that are not exposed as __op or under builtins to turn
+// the internal PosIdx back into a line and column number, respectively. exposing
+// these primops in any way would at best be not useful and at worst create wildly
+// indeterministic eval results depending on parse order of files.
+//
+// in a simpler world this would instead be implemented as another kind of thunk,
+// but each type of thunk has an associated runtime cost in the current evaluator.
+// as with black holes this cost is too high to justify another thunk type to check
+// for in the very hot path that is forceValue.
+static struct LazyPosAcessors {
+    PrimOp primop_lineOfPos{
+        .arity = 1,
+        .fun = [] (EvalState & state, PosIdx pos, Value * * args, Value & v) {
+            v.mkInt(state.positions[PosIdx(args[0]->integer)].line);
+        }
+    };
+    PrimOp primop_columnOfPos{
+        .arity = 1,
+        .fun = [] (EvalState & state, PosIdx pos, Value * * args, Value & v) {
+            v.mkInt(state.positions[PosIdx(args[0]->integer)].column);
+        }
+    };
+
+    Value lineOfPos, columnOfPos;
+
+    LazyPosAcessors()
+    {
+        lineOfPos.mkPrimOp(&primop_lineOfPos);
+        columnOfPos.mkPrimOp(&primop_columnOfPos);
+    }
+
+    void operator()(EvalState & state, const PosIdx pos, Value & line, Value & column)
+    {
+        Value * posV = state.allocValue();
+        posV->mkInt(pos.id);
+        line.mkApp(&lineOfPos, posV);
+        column.mkApp(&columnOfPos, posV);
+    }
+} makeLazyPosAccessors;
+
+void makePositionThunks(EvalState & state, const PosIdx pos, Value & line, Value & column)
+{
+    makeLazyPosAccessors(state, pos, line, column);
+}
+
 /* Dynamic version of the `?' operator. */
 static void prim_hasAttr(EvalState & state, const PosIdx pos, Value * * args, Value & v)
 {
@@ -4522,11 +4570,9 @@ void EvalState::createBaseEnv()
     addConstant("__nixPath", v, {
         .type = nList,
         .doc = R"(
-          List of search path entries used to resolve [lookup paths](@docroot@/language/constructs/lookup-path.md).
+          The value of the [`nix-path` configuration setting](@docroot@/command-ref/conf-file.md#conf-nix-path): a list of search path entries used to resolve [lookup paths](@docroot@/language/constructs/lookup-path.md).
 
-          Lookup path expressions can be
+          Lookup path expressions are [desugared](https://en.wikipedia.org/wiki/Syntactic_sugar) using this and
-          [desugared](https://en.wikipedia.org/wiki/Syntactic_sugar)
-          using this and
           [`builtins.findFile`](./builtins.html#builtins-findFile):
 
           ```nix

src/libexpr/primops.hh

@@ -51,4 +51,6 @@ void prim_importNative(EvalState & state, const PosIdx pos, Value * * args, Valu
  */
 void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v);
 
+void makePositionThunks(EvalState & state, const PosIdx pos, Value & line, Value & column);
+
 }

src/libexpr/primops/context.cc

@@ -137,14 +137,14 @@ static RegisterPrimOp primop_addDrvOutputDependencies({
     .name = "__addDrvOutputDependencies",
     .args = {"s"},
     .doc = R"(
-      Create a copy of the given string where a single consant string context element is turned into a "derivation deep" string context element.
+      Create a copy of the given string where a single constant string context element is turned into a "derivation deep" string context element.
 
       The store path that is the constant string context element should point to a valid derivation, and end in `.drv`.
 
       The original string context element must not be empty or have multiple elements, and it must not have any other type of element other than a constant or derivation deep element.
       The latter is supported so this function is idempotent.
 
-      This is the opposite of [`builtins.unsafeDiscardOutputDependency`](#builtins-addDrvOutputDependencies).
+      This is the opposite of [`builtins.unsafeDiscardOutputDependency`](#builtins-unsafeDiscardOutputDependency).
     )",
     .fun = prim_addDrvOutputDependencies
 });
@@ -246,7 +246,7 @@ static RegisterPrimOp primop_getContext({
 
 /* Append the given context to a given string.
 
-   See the commentary above unsafeGetContext for details of the
+   See the commentary above getContext for details of the
    context representation.
 */
 static void prim_appendContext(EvalState & state, const PosIdx pos, Value * * args, Value & v)

src/libexpr/primops/fetchMercurial.cc

@@ -64,8 +64,7 @@ static void prim_fetchMercurial(EvalState & state, const PosIdx pos, Value * * a
     if (rev) attrs.insert_or_assign("rev", rev->gitRev());
     auto input = fetchers::Input::fromAttrs(std::move(attrs));
 
-    // FIXME: use name
+    auto [storePath, input2] = input.fetchToStore(state.store);
-    auto [storePath, input2] = input.fetch(state.store);
 
     auto attrs2 = state.buildBindings(8);
     state.mkStorePathString(storePath, attrs2.alloc(state.sOutPath));

src/libexpr/primops/fetchTree.cc

@@ -182,7 +182,7 @@ static void fetchTree(
 
     state.checkURI(input.toURLString());
 
-    auto [storePath, input2] = input.fetch(state.store);
+    auto [storePath, input2] = input.fetchToStore(state.store);
 
     state.allowPath(storePath);
 

src/libexpr/print-options.hh

@@ -8,6 +8,29 @@
 
 namespace nix {
 
+/**
+ * How errors should be handled when printing values.
+ */
+enum class ErrorPrintBehavior {
+    /**
+     * Print the first line of the error in brackets: `«error: oh no!»`
+     */
+    Print,
+    /**
+     * Throw the error to the code that attempted to print the value, instead
+     * of suppressing it it.
+     */
+    Throw,
+    /**
+     * Only throw the error if encountered at the top level of the expression.
+     *
+     * This will cause expressions like `builtins.throw "uh oh!"` to throw
+     * errors, but will print attribute sets and other nested structures
+     * containing values that error (like `nixpkgs`) normally.
+     */
+    ThrowTopLevel,
+};
+
 /**
  * Options for printing Nix values.
  */
@@ -68,6 +91,11 @@ struct PrintOptions
      */
     size_t prettyIndent = 0;
 
+    /**
+     * How to handle errors encountered while printing values.
+     */
+    ErrorPrintBehavior errors = ErrorPrintBehavior::Print;
+
     /**
      * True if pretty-printing is enabled.
      */
@@ -86,7 +114,7 @@ static PrintOptions errorPrintOptions = PrintOptions {
     .maxDepth = 10,
     .maxAttrs = 10,
     .maxListItems = 10,
-    .maxStringLength = 1024
+    .maxStringLength = 1024,
 };
 
 }

src/libexpr/print.cc

@@ -271,25 +271,21 @@ private:
 
     void printDerivation(Value & v)
     {
-        try {
+        Bindings::iterator i = v.attrs->find(state.sDrvPath);
-            Bindings::iterator i = v.attrs->find(state.sDrvPath);
+        NixStringContext context;
-            NixStringContext context;
+        std::string storePath;
-            std::string storePath;
+        if (i != v.attrs->end())
-            if (i != v.attrs->end())
+            storePath = state.store->printStorePath(state.coerceToStorePath(i->pos, *i->value, context, "while evaluating the drvPath of a derivation"));
-                storePath = state.store->printStorePath(state.coerceToStorePath(i->pos, *i->value, context, "while evaluating the drvPath of a derivation"));
 
-            if (options.ansiColors)
+        if (options.ansiColors)
-                output << ANSI_GREEN;
+            output << ANSI_GREEN;
-            output << "«derivation";
+        output << "«derivation";
-            if (!storePath.empty()) {
+        if (!storePath.empty()) {
-                output << " " << storePath;
+            output << " " << storePath;
-            }
-            output << "»";
-            if (options.ansiColors)
-                output << ANSI_NORMAL;
-        } catch (Error & e) {
-            printError_(e);
         }
+        output << "»";
+        if (options.ansiColors)
+            output << ANSI_NORMAL;
     }
 
     bool shouldPrettyPrintAttrs(AttrVec & v)
@@ -510,64 +506,68 @@ private:
         output.flush();
         checkInterrupt();
 
-        if (options.force) {
+        try {
-            try {
+            if (options.force) {
                 state.forceValue(v, v.determinePos(noPos));
-            } catch (Error & e) {
-                printError_(e);
-                return;
             }
-        }
 
-        switch (v.type()) {
+            switch (v.type()) {
 
-        case nInt:
+            case nInt:
-            printInt(v);
+                printInt(v);
-            break;
+                break;
 
-        case nFloat:
+            case nFloat:
-            printFloat(v);
+                printFloat(v);
-            break;
+                break;
 
-        case nBool:
+            case nBool:
-            printBool(v);
+                printBool(v);
-            break;
+                break;
 
-        case nString:
+            case nString:
-            printString(v);
+                printString(v);
-            break;
+                break;
 
-        case nPath:
+            case nPath:
-            printPath(v);
+                printPath(v);
-            break;
+                break;
 
-        case nNull:
+            case nNull:
-            printNull();
+                printNull();
-            break;
+                break;
 
-        case nAttrs:
+            case nAttrs:
-            printAttrs(v, depth);
+                printAttrs(v, depth);
-            break;
+                break;
 
-        case nList:
+            case nList:
-            printList(v, depth);
+                printList(v, depth);
-            break;
+                break;
 
-        case nFunction:
+            case nFunction:
-            printFunction(v);
+                printFunction(v);
-            break;
+                break;
 
-        case nThunk:
+            case nThunk:
-            printThunk(v);
+                printThunk(v);
-            break;
+                break;
 
-        case nExternal:
+            case nExternal:
-            printExternal(v);
+                printExternal(v);
-            break;
+                break;
 
-        default:
+            default:
-            printUnknown();
+                printUnknown();
-            break;
+                break;
+            }
+        } catch (Error & e) {
+            if (options.errors == ErrorPrintBehavior::Throw
+                || (options.errors == ErrorPrintBehavior::ThrowTopLevel
+                    && depth == 0)) {
+                throw;
+            }
+            printError_(e);
         }
     }
 

src/libfetchers/fetchers.cc

@@ -161,7 +161,7 @@ bool Input::contains(const Input & other) const
     return false;
 }
 
-std::pair<StorePath, Input> Input::fetch(ref<Store> store) const
+std::pair<StorePath, Input> Input::fetchToStore(ref<Store> store) const
 {
     if (!scheme)
         throw Error("cannot fetch unsupported input '%s'", attrsToJSON(toAttrs()));
@@ -186,56 +186,85 @@ std::pair<StorePath, Input> Input::fetch(ref<Store> store) const
 
     auto [storePath, input] = [&]() -> std::pair<StorePath, Input> {
         try {
-            return scheme->fetch(store, *this);
+            auto [accessor, final] = getAccessorUnchecked(store);
+
+            auto storePath = nix::fetchToStore(*store, SourcePath(accessor), FetchMode::Copy, final.getName());
+
+            auto narHash = store->queryPathInfo(storePath)->narHash;
+            final.attrs.insert_or_assign("narHash", narHash.to_string(HashFormat::SRI, true));
+
+            scheme->checkLocks(*this, final);
+
+            return {storePath, final};
         } catch (Error & e) {
             e.addTrace({}, "while fetching the input '%s'", to_string());
             throw;
         }
     }();
 
-    auto narHash = store->queryPathInfo(storePath)->narHash;
-    input.attrs.insert_or_assign("narHash", narHash.to_string(HashFormat::SRI, true));
-
-    if (auto prevNarHash = getNarHash()) {
-        if (narHash != *prevNarHash)
-            throw Error((unsigned int) 102, "NAR hash mismatch in input '%s' (%s), expected '%s', got '%s'",
-                to_string(),
-                store->printStorePath(storePath),
-                prevNarHash->to_string(HashFormat::SRI, true),
-                narHash.to_string(HashFormat::SRI, true));
-    }
-
-    if (auto prevLastModified = getLastModified()) {
-        if (input.getLastModified() != prevLastModified)
-            throw Error("'lastModified' attribute mismatch in input '%s', expected %d",
-                input.to_string(), *prevLastModified);
-    }
-
-    if (auto prevRev = getRev()) {
-        if (input.getRev() != prevRev)
-            throw Error("'rev' attribute mismatch in input '%s', expected %s",
-                input.to_string(), prevRev->gitRev());
-    }
-
-    if (auto prevRevCount = getRevCount()) {
-        if (input.getRevCount() != prevRevCount)
-            throw Error("'revCount' attribute mismatch in input '%s', expected %d",
-                input.to_string(), *prevRevCount);
-    }
-
     return {std::move(storePath), input};
 }
 
+void InputScheme::checkLocks(const Input & specified, const Input & final) const
+{
+    if (auto prevNarHash = specified.getNarHash()) {
+        if (final.getNarHash() != prevNarHash) {
+            if (final.getNarHash())
+                throw Error((unsigned int) 102, "NAR hash mismatch in input '%s', expected '%s' but got '%s'",
+                    specified.to_string(), prevNarHash->to_string(HashFormat::SRI, true), final.getNarHash()->to_string(HashFormat::SRI, true));
+            else
+                throw Error((unsigned int) 102, "NAR hash mismatch in input '%s', expected '%s' but got none",
+                    specified.to_string(), prevNarHash->to_string(HashFormat::SRI, true));
+        }
+    }
+
+    if (auto prevLastModified = specified.getLastModified()) {
+        if (final.getLastModified() != prevLastModified)
+            throw Error("'lastModified' attribute mismatch in input '%s', expected %d",
+                final.to_string(), *prevLastModified);
+    }
+
+    if (auto prevRev = specified.getRev()) {
+        if (final.getRev() != prevRev)
+            throw Error("'rev' attribute mismatch in input '%s', expected %s",
+                final.to_string(), prevRev->gitRev());
+    }
+
+    if (auto prevRevCount = specified.getRevCount()) {
+        if (final.getRevCount() != prevRevCount)
+            throw Error("'revCount' attribute mismatch in input '%s', expected %d",
+                final.to_string(), *prevRevCount);
+    }
+}
+
 std::pair<ref<InputAccessor>, Input> Input::getAccessor(ref<Store> store) const
 {
     try {
-        return scheme->getAccessor(store, *this);
+        auto [accessor, final] = getAccessorUnchecked(store);
+
+        scheme->checkLocks(*this, final);
+
+        return {accessor, std::move(final)};
     } catch (Error & e) {
         e.addTrace({}, "while fetching the input '%s'", to_string());
         throw;
     }
 }
 
+std::pair<ref<InputAccessor>, Input> Input::getAccessorUnchecked(ref<Store> store) const
+{
+    // FIXME: cache the accessor
+
+    if (!scheme)
+        throw Error("cannot fetch unsupported input '%s'", attrsToJSON(toAttrs()));
+
+    auto [accessor, final] = scheme->getAccessor(store, *this);
+
+    accessor->fingerprint = scheme->getFingerprint(store, final);
+
+    return {accessor, std::move(final)};
+}
+
 Input Input::applyOverrides(
     std::optional<std::string> ref,
     std::optional<Hash> rev) const
@@ -372,18 +401,6 @@ void InputScheme::clone(const Input & input, const Path & destDir) const
     throw Error("do not know how to clone input '%s'", input.to_string());
 }
 
-std::pair<StorePath, Input> InputScheme::fetch(ref<Store> store, const Input & input)
-{
-    auto [accessor, input2] = getAccessor(store, input);
-    auto storePath = fetchToStore(*store, SourcePath(accessor), FetchMode::Copy, input2.getName());
-    return {storePath, input2};
-}
-
-std::pair<ref<InputAccessor>, Input> InputScheme::getAccessor(ref<Store> store, const Input & input) const
-{
-    throw UnimplementedError("InputScheme must implement fetch() or getAccessor()");
-}
-
 std::optional<ExperimentalFeature> InputScheme::experimentalFeature() const
 {
     return {};

src/libfetchers/fetchers.hh

@@ -80,10 +80,21 @@ public:
      * Fetch the entire input into the Nix store, returning the
      * location in the Nix store and the locked input.
      */
-    std::pair<StorePath, Input> fetch(ref<Store> store) const;
+    std::pair<StorePath, Input> fetchToStore(ref<Store> store) const;
 
+    /**
+     * Return an InputAccessor that allows access to files in the
+     * input without copying it to the store. Also return a possibly
+     * unlocked input.
+     */
     std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store) const;
 
+private:
+
+    std::pair<ref<InputAccessor>, Input> getAccessorUnchecked(ref<Store> store) const;
+
+public:
+
     Input applyOverrides(
         std::optional<std::string> ref,
         std::optional<Hash> rev) const;
@@ -173,9 +184,7 @@ struct InputScheme
         std::string_view contents,
         std::optional<std::string> commitMsg) const;
 
-    virtual std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input);
+    virtual std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const = 0;
-
-    virtual std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const;
 
     /**
      * Is this `InputScheme` part of an experimental feature?
@@ -202,6 +211,14 @@ struct InputScheme
      */
     virtual bool isLocked(const Input & input) const
     { return false; }
+
+    /**
+     * Check the locking attributes in `final` against
+     * `specified`. E.g. if `specified` has a `rev` attribute, then
+     * `final` must have the same `rev` attribute. Throw an exception
+     * if there is a mismatch.
+     */
+    virtual void checkLocks(const Input & specified, const Input & final) const;
 };
 
 void registerInputScheme(std::shared_ptr<InputScheme> && fetcher);

src/libfetchers/git.cc

@@ -761,8 +761,6 @@ struct GitInputScheme : InputScheme
             ? getAccessorFromCommit(store, repoInfo, std::move(input))
             : getAccessorFromWorkdir(store, repoInfo, std::move(input));
 
-        accessor->fingerprint = final.getFingerprint(store);
-
         return {accessor, std::move(final)};
     }
 

src/libfetchers/github.cc

@@ -98,6 +98,10 @@ struct GitArchiveInputScheme : InputScheme
         if (ref) input.attrs.insert_or_assign("ref", *ref);
         if (host_url) input.attrs.insert_or_assign("host", *host_url);
 
+        auto narHash = url.query.find("narHash");
+        if (narHash != url.query.end())
+            input.attrs.insert_or_assign("narHash", narHash->second);
+
         return input;
     }
 
@@ -111,6 +115,7 @@ struct GitArchiveInputScheme : InputScheme
             "narHash",
             "lastModified",
             "host",
+            "treeHash",
         };
     }
 
@@ -134,10 +139,13 @@ struct GitArchiveInputScheme : InputScheme
         assert(!(ref && rev));
         if (ref) path += "/" + *ref;
         if (rev) path += "/" + rev->to_string(HashFormat::Base16, false);
-        return ParsedURL {
+        auto url = ParsedURL {
             .scheme = std::string { schemeName() },
             .path = path,
         };
+        if (auto narHash = input.getNarHash())
+            url.query.insert_or_assign("narHash", narHash->to_string(HashFormat::SRI, true));
+        return url;
     }
 
     Input applyOverrides(
@@ -268,15 +276,15 @@ struct GitArchiveInputScheme : InputScheme
     {
         auto [input, tarballInfo] = downloadArchive(store, _input);
 
+        #if 0
         input.attrs.insert_or_assign("treeHash", tarballInfo.treeHash.gitRev());
+        #endif
         input.attrs.insert_or_assign("lastModified", uint64_t(tarballInfo.lastModified));
 
         auto accessor = getTarballCache()->getAccessor(tarballInfo.treeHash, false);
 
         accessor->setPathDisplay("«" + input.to_string() + "»");
 
-        accessor->fingerprint = input.getFingerprint(store);
-
         return {accessor, input};
     }
 

src/libfetchers/indirect.cc

@@ -97,7 +97,7 @@ struct IndirectInputScheme : InputScheme
         return input;
     }
 
-    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input) override
+    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const override
     {
         throw Error("indirect input '%s' cannot be fetched directly", input.to_string());
     }

src/libfetchers/mercurial.cc

@@ -6,8 +6,8 @@
 #include "tarfile.hh"
 #include "store-api.hh"
 #include "url-parts.hh"
+#include "fs-input-accessor.hh"
 #include "posix-source-accessor.hh"
-
 #include "fetch-settings.hh"
 
 #include <sys/time.h>
@@ -161,9 +161,9 @@ struct MercurialInputScheme : InputScheme
         return {isLocal, isLocal ? url.path : url.base};
     }
 
-    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & _input) override
+    StorePath fetchToStore(ref<Store> store, Input & input) const
     {
-        Input input(_input);
+        auto origRev = input.getRev();
 
         auto name = input.getName();
 
@@ -218,7 +218,7 @@ struct MercurialInputScheme : InputScheme
                     FileIngestionMethod::Recursive, HashAlgorithm::SHA256, {},
                     filter);
 
-                return {std::move(storePath), input};
+                return storePath;
             }
         }
 
@@ -242,13 +242,12 @@ struct MercurialInputScheme : InputScheme
             });
         };
 
-        auto makeResult = [&](const Attrs & infoAttrs, StorePath && storePath)
+        auto makeResult = [&](const Attrs & infoAttrs, const StorePath & storePath) -> StorePath
-            -> std::pair<StorePath, Input>
         {
             assert(input.getRev());
-            assert(!_input.getRev() || _input.getRev() == input.getRev());
+            assert(!origRev || origRev == input.getRev());
             input.attrs.insert_or_assign("revCount", getIntAttr(infoAttrs, "revCount"));
-            return {std::move(storePath), input};
+            return storePath;
         };
 
         if (input.getRev()) {
@@ -329,7 +328,7 @@ struct MercurialInputScheme : InputScheme
             {"revCount", (uint64_t) revCount},
         });
 
-        if (!_input.getRev())
+        if (!origRev)
             getCache()->add(
                 *store,
                 unlockedAttrs,
@@ -347,6 +346,15 @@ struct MercurialInputScheme : InputScheme
         return makeResult(infoAttrs, std::move(storePath));
     }
 
+    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    {
+        Input input(_input);
+
+        auto storePath = fetchToStore(store, input);
+
+        return {makeStorePathAccessor(store, storePath), input};
+    }
+
     bool isLocked(const Input & input) const override
     {
         return (bool) input.getRev();

src/libfetchers/path.cc

@@ -1,6 +1,8 @@
 #include "fetchers.hh"
 #include "store-api.hh"
 #include "archive.hh"
+#include "fs-input-accessor.hh"
+#include "posix-source-accessor.hh"
 
 namespace nix::fetchers {
 
@@ -87,6 +89,15 @@ struct PathInputScheme : InputScheme
         writeFile((CanonPath(getAbsPath(input)) / path).abs(), contents);
     }
 
+    std::optional<std::string> isRelative(const Input & input) const
+    {
+        auto path = getStrAttr(input.attrs, "path");
+        if (hasPrefix(path, "/"))
+            return std::nullopt;
+        else
+            return path;
+    }
+
     bool isLocked(const Input & input) const override
     {
         return (bool) input.getNarHash();
@@ -102,7 +113,7 @@ struct PathInputScheme : InputScheme
         throw Error("cannot fetch input '%s' because it uses a relative path", input.to_string());
     }
 
-    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & _input) override
+    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
     {
         Input input(_input);
         std::string absPath;
@@ -144,7 +155,24 @@ struct PathInputScheme : InputScheme
         }
         input.attrs.insert_or_assign("lastModified", uint64_t(mtime));
 
-        return {std::move(*storePath), input};
+        return {makeStorePathAccessor(store, *storePath), std::move(input)};
+    }
+
+    std::optional<std::string> getFingerprint(ref<Store> store, const Input & input) const override
+    {
+        if (isRelative(input))
+            return std::nullopt;
+
+        /* If this path is in the Nix store, use the hash of the
+           store object and the subpath. */
+        auto path = getAbsPath(input);
+        try {
+            auto [storePath, subPath] = store->toStorePath(path.abs());
+            auto info = store->queryPathInfo(storePath);
+            return fmt("path:%s:%s", info->narHash.to_string(HashFormat::Base16, false), subPath);
+        } catch (Error &) {
+            return std::nullopt;
+        }
     }
 
     std::optional<ExperimentalFeature> experimentalFeature() const override

src/libstore/build-result.hh

@@ -123,6 +123,11 @@ struct KeyedBuildResult : BuildResult
      * The derivation we built or the store path we substituted.
      */
     DerivedPath path;
+
+    // Hack to work around a gcc "may be used uninitialized" warning.
+    KeyedBuildResult(BuildResult res, DerivedPath path)
+        : BuildResult(std::move(res)), path(std::move(path))
+    { }
 };
 
 }

src/libstore/build/local-derivation-goal.cc

@@ -2480,6 +2480,7 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
                         CanonPath { tmpDir + "/tmp" }).hash;
                 }
                 }
+                assert(false);
             }();
 
             ValidPathInfo newInfo0 {
@@ -2543,6 +2544,12 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
             [&](const DerivationOutput::CAFixed & dof) {
                 auto & wanted = dof.ca.hash;
 
+                // Replace the output by a fresh copy of itself to make sure
+                // that there's no stale file descriptor pointing to it
+                Path tmpOutput = actualPath + ".tmp";
+                copyFile(actualPath, tmpOutput, true);
+                renameFile(tmpOutput, actualPath);
+
                 auto newInfo0 = newInfoFromCA(DerivationOutput::CAFloating {
                     .method = dof.ca.method,
                     .hashAlgo = wanted.algo,

src/libstore/build/sandbox-defaults.sb

@@ -45,7 +45,7 @@ R""(
 ; allow it if the package explicitly asks for it.
 (if (param "_ALLOW_LOCAL_NETWORKING")
     (begin
-      (allow network* (local ip) (local tcp) (local udp))
+      (allow network* (remote ip "localhost:*"))
 
       ; Allow access to /etc/resolv.conf (which is a symlink to
       ; /private/var/run/resolv.conf).

src/libstore/daemon.cc

@@ -415,6 +415,8 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
                     // Use NAR; Git is not a serialization method
                     dumpMethod = FileSerialisationMethod::Recursive;
                     break;
+                default:
+                    assert(false);
                 }
                 // TODO these two steps are essentially RemoteStore::addCAToStore. Move it up to Store.
                 auto path = store->addToStoreFromDump(source, name, dumpMethod, contentAddressMethod, hashAlgo, refs, repair);

src/libstore/remote-store.cc

@@ -527,6 +527,8 @@ StorePath RemoteStore::addToStoreFromDump(
         // Use NAR; Git is not a serialization method
         fsm = FileSerialisationMethod::Recursive;
         break;
+    default:
+        assert(false);
     }
     if (fsm != dumpMethod)
         unsupported("RemoteStore::addToStoreFromDump doesn't support this `dumpMethod` `hashMethod` combination");

src/libutil/current-process.cc

@@ -38,6 +38,11 @@ unsigned int getMaxCPU()
 
         auto cpuMax = readFile(cpuFile);
         auto cpuMaxParts = tokenizeString<std::vector<std::string>>(cpuMax, " \n");
+
+        if (cpuMaxParts.size() != 2) {
+            return 0;
+        }
+
         auto quota = cpuMaxParts[0];
         auto period = cpuMaxParts[1];
         if (quota != "max")

src/libutil/experimental-features.cc

@@ -1,4 +1,5 @@
 #include "experimental-features.hh"
+#include "fmt.hh"
 #include "util.hh"
 
 #include "nlohmann/json.hpp"
@@ -10,6 +11,7 @@ struct ExperimentalFeatureDetails
     ExperimentalFeature tag;
     std::string_view name;
     std::string_view description;
+    std::string_view trackingUrl;
 };
 
 /**
@@ -35,6 +37,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             [__contentAddressed](@docroot@/language/advanced-attributes.md#adv-attr-__contentAddressed)
             for details.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/35",
     },
     {
         .tag = Xp::ImpureDerivations,
@@ -65,6 +68,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
 
             This is a more explicit alternative to using [`builtins.currentTime`](@docroot@/language/builtin-constants.md#builtins-currentTime).
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/42",
     },
     {
         .tag = Xp::Flakes,
@@ -73,6 +77,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             Enable flakes. See the manual entry for [`nix
             flake`](@docroot@/command-ref/new-cli/nix3-flake.md) for details.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/27",
     },
     {
         .tag = Xp::FetchTree,
@@ -86,6 +91,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
 
             Enabling just this feature serves as a "release candidate", allowing users to try it out in isolation.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/31",
     },
     {
         .tag = Xp::NixCommand,
@@ -94,6 +100,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             Enable the new `nix` subcommands. See the manual on
             [`nix`](@docroot@/command-ref/new-cli/nix.md) for details.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/28",
     },
     {
         .tag = Xp::GitHashing,
@@ -102,6 +109,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             Allow creating (content-addressed) store objects which are hashed via Git's hashing algorithm.
             These store objects will not be understandable by older versions of Nix.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/41",
     },
     {
         .tag = Xp::RecursiveNix,
@@ -143,6 +151,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             already in the build inputs or built by a previous recursive Nix
             call.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/47",
     },
     {
         .tag = Xp::NoUrlLiterals,
@@ -184,6 +193,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             containing parameters have to be quoted anyway, and unquoted URLs
             may confuse external tooling.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/44",
     },
     {
         .tag = Xp::FetchClosure,
@@ -191,6 +201,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
         .description = R"(
             Enable the use of the [`fetchClosure`](@docroot@/language/builtins.md#builtins-fetchClosure) built-in function in the Nix language.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/40",
     },
     {
         .tag = Xp::ReplFlake,
@@ -200,6 +211,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
 
             Allow passing [installables](@docroot@/command-ref/new-cli/nix.md#installables) to `nix repl`, making its interface consistent with the other experimental commands.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/32",
     },
     {
         .tag = Xp::AutoAllocateUids,
@@ -208,6 +220,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             Allows Nix to automatically pick UIDs for builds, rather than creating
             `nixbld*` user accounts. See the [`auto-allocate-uids`](@docroot@/command-ref/conf-file.md#conf-auto-allocate-uids) setting for details.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/34",
     },
     {
         .tag = Xp::Cgroups,
@@ -216,6 +229,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             Allows Nix to execute builds inside cgroups. See
             the [`use-cgroups`](@docroot@/command-ref/conf-file.md#conf-use-cgroups) setting for details.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/36",
     },
     {
         .tag = Xp::DaemonTrustOverride,
@@ -226,6 +240,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             useful for various experiments with `nix-daemon --stdio`
             networking.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/38",
     },
     {
         .tag = Xp::DynamicDerivations,
@@ -239,6 +254,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
               - dependencies in derivations on the outputs of
                 derivations that are themselves derivations outputs.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/39",
     },
     {
         .tag = Xp::ParseTomlTimestamps,
@@ -246,6 +262,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
         .description = R"(
             Allow parsing of timestamps in builtins.fromTOML.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/45",
     },
     {
         .tag = Xp::ReadOnlyLocalStore,
@@ -253,6 +270,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
         .description = R"(
             Allow the use of the `read-only` parameter in [local store](@docroot@/store/types/local-store.md) URIs.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/46",
     },
     {
         .tag = Xp::LocalOverlayStore,
@@ -260,7 +278,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
         .description = R"(
             Allow the use of [local overlay store](@docroot@/command-ref/new-cli/nix3-help-stores.md#local-overlay-store).
         )",
-        .trackingUrl = ""https://github.com/NixOS/nix/milestone/50",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/50",
     },
     {
         .tag = Xp::ConfigurableImpureEnv,
@@ -268,6 +286,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
         .description = R"(
             Allow the use of the [impure-env](@docroot@/command-ref/conf-file.md#conf-impure-env) setting.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/37",
     },
     {
         .tag = Xp::MountedSSHStore,
@@ -275,6 +294,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
         .description = R"(
             Allow the use of the [`mounted SSH store`](@docroot@/command-ref/new-cli/nix3-help-stores.html#experimental-ssh-store-with-filesytem-mounted).
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/43",
     },
     {
         .tag = Xp::VerifiedFetches,
@@ -282,6 +302,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
         .description = R"(
             Enables verification of git commit signatures through the [`fetchGit`](@docroot@/language/builtins.md#builtins-fetchGit) built-in.
         )",
+        .trackingUrl = "https://github.com/NixOS/nix/milestone/48",
     },
 }};
 
@@ -320,9 +341,12 @@ std::string_view showExperimentalFeature(const ExperimentalFeature tag)
 nlohmann::json documentExperimentalFeatures()
 {
     StringMap res;
-    for (auto & xpFeature : xpFeatureDetails)
+    for (auto & xpFeature : xpFeatureDetails) {
-        res[std::string { xpFeature.name }] =
+        std::stringstream docOss;
-            trim(stripIndentation(xpFeature.description));
+        docOss << stripIndentation(xpFeature.description);
+        docOss << fmt("\nRefer to [%1% tracking issue](%2%) for feature tracking.", xpFeature.name, xpFeature.trackingUrl);
+        res[std::string{xpFeature.name}] = trim(docOss.str());
+    }
     return (nlohmann::json) res;
 }
 

src/libutil/file-content-address.cc

@@ -123,7 +123,7 @@ Hash hashPath(
     case FileIngestionMethod::Git:
         return git::dumpHash(ht, accessor, path, filter).hash;
     }
-
+    assert(false);
 }
 
 }

src/libutil/file-system.cc

@@ -617,6 +617,11 @@ void copy(const fs::directory_entry & from, const fs::path & to, bool andDelete)
     }
 }
 
+void copyFile(const Path & oldPath, const Path & newPath, bool andDelete)
+{
+    return copy(fs::directory_entry(fs::path(oldPath)), fs::path(newPath), andDelete);
+}
+
 void renameFile(const Path & oldName, const Path & newName)
 {
     fs::rename(oldName, newName);

src/libutil/file-system.hh

@@ -186,6 +186,13 @@ void renameFile(const Path & src, const Path & dst);
  */
 void moveFile(const Path & src, const Path & dst);
 
+/**
+ * Recursively copy the content of `oldPath` to `newPath`. If `andDelete` is
+ * `true`, then also remove `oldPath` (making this equivalent to `moveFile`, but
+ * with the guaranty that the destination will be “fresh”, with no stale inode
+ * or file descriptor pointing to it).
+ */
+void copyFile(const Path & oldPath, const Path & newPath, bool andDelete);
 
 /**
  * Automatic cleanup of resources.

src/libutil/fmt.hh

@@ -8,7 +8,6 @@
 
 namespace nix {
 
-namespace {
 /**
  * A helper for writing `boost::format` expressions.
  *
@@ -35,14 +34,13 @@ inline void formatHelper(F & f, const T & x, const Args & ... args)
 /**
  * Set the correct exceptions for `fmt`.
  */
-void setExceptions(boost::format & fmt)
+inline void setExceptions(boost::format & fmt)
 {
     fmt.exceptions(
         boost::io::all_error_bits ^
         boost::io::too_many_args_bit ^
         boost::io::too_few_args_bit);
 }
-}
 
 /**
  * A helper for writing a `boost::format` expression to a string.

src/libutil/git.cc

@@ -56,31 +56,63 @@ void parseBlob(
     FileSystemObjectSink & sink,
     const Path & sinkPath,
     Source & source,
-    bool executable,
+    BlobMode blobMode,
     const ExperimentalFeatureSettings & xpSettings)
 {
     xpSettings.require(Xp::GitHashing);
 
-    sink.createRegularFile(sinkPath, [&](auto & crf) {
+    unsigned long long size = std::stoi(getStringUntil(source, 0));
-        if (executable)
-            crf.isExecutable();
 
-        unsigned long long size = std::stoi(getStringUntil(source, 0));
+    auto doRegularFile = [&](bool executable) {
+        sink.createRegularFile(sinkPath, [&](auto & crf) {
+            if (executable)
+                crf.isExecutable();
 
-        crf.preallocateContents(size);
+            crf.preallocateContents(size);
 
-        unsigned long long left = size;
+            unsigned long long left = size;
-        std::string buf;
+            std::string buf;
-        buf.reserve(65536);
+            buf.reserve(65536);
 
-        while (left) {
+            while (left) {
+                checkInterrupt();
+                buf.resize(std::min((unsigned long long)buf.capacity(), left));
+                source(buf);
+                crf(buf);
+                left -= buf.size();
+            }
+        });
+    };
+
+    switch (blobMode) {
+
+    case BlobMode::Regular:
+        doRegularFile(false);
+        break;
+
+    case BlobMode::Executable:
+        doRegularFile(true);
+        break;
+
+    case BlobMode::Symlink:
+    {
+        std::string target;
+        target.resize(size, '0');
+        target.reserve(size);
+        for (size_t n = 0; n < target.size();) {
             checkInterrupt();
-            buf.resize(std::min((unsigned long long)buf.capacity(), left));
+            n += source.read(
-            source(buf);
+                const_cast<char *>(target.c_str()) + n,
-            crf(buf);
+                target.size() - n);
-            left -= buf.size();
         }
-    });
+
+        sink.createSymlink(sinkPath, target);
+        break;
+    }
+
+    default:
+        assert(false);
+    }
 }
 
 void parseTree(
@@ -142,7 +174,7 @@ void parse(
     FileSystemObjectSink & sink,
     const Path & sinkPath,
     Source & source,
-    bool executable,
+    BlobMode rootModeIfBlob,
     std::function<SinkHook> hook,
     const ExperimentalFeatureSettings & xpSettings)
 {
@@ -152,7 +184,7 @@ void parse(
 
     switch (type) {
     case ObjectType::Blob:
-        parseBlob(sink, sinkPath, source, executable, xpSettings);
+        parseBlob(sink, sinkPath, source, rootModeIfBlob, xpSettings);
         break;
     case ObjectType::Tree:
         parseTree(sink, sinkPath, source, hook, xpSettings);
@@ -177,7 +209,7 @@ std::optional<Mode> convertMode(SourceAccessor::Type type)
 
 void restore(FileSystemObjectSink & sink, Source & source, std::function<RestoreHook> hook)
 {
-    parse(sink, "", source, false, [&](Path name, TreeEntry entry) {
+    parse(sink, "", source, BlobMode::Regular, [&](Path name, TreeEntry entry) {
         auto [accessor, from] = hook(entry.hash);
         auto stat = accessor->lstat(from);
         auto gotOpt = convertMode(stat.type);
@@ -275,6 +307,13 @@ Mode dump(
     }
 
     case SourceAccessor::tSymlink:
+    {
+        auto target = accessor.readLink(path);
+        dumpBlobPrefix(target.size(), sink, xpSettings);
+        sink(target);
+        return Mode::Symlink;
+    }
+
     case SourceAccessor::tMisc:
     default:
         throw Error("file '%1%' has an unsupported type", path);

src/libutil/git.hh

@@ -75,10 +75,23 @@ ObjectType parseObjectType(
     Source & source,
     const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
 
+/**
+ * These 3 modes are represented by blob objects.
+ *
+ * Sometimes we need this information to disambiguate how a blob is
+ * being used to better match our own "file system object" data model.
+ */
+enum struct BlobMode : RawMode
+{
+    Regular = static_cast<RawMode>(Mode::Regular),
+    Executable = static_cast<RawMode>(Mode::Executable),
+    Symlink = static_cast<RawMode>(Mode::Symlink),
+};
+
 void parseBlob(
     FileSystemObjectSink & sink, const Path & sinkPath,
     Source & source,
-    bool executable,
+    BlobMode blobMode,
     const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
 
 void parseTree(
@@ -89,11 +102,15 @@ void parseTree(
 
 /**
  * Helper putting the previous three `parse*` functions together.
+ *
+ * @rootModeIfBlob How to interpret a root blob, for which there is no
+ * disambiguating dir entry to answer that questino. If the root it not
+ * a blob, this is ignored.
  */
 void parse(
     FileSystemObjectSink & sink, const Path & sinkPath,
     Source & source,
-    bool executable,
+    BlobMode rootModeIfBlob,
     std::function<SinkHook> hook,
     const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
 

src/libutil/position.cc

@@ -29,32 +29,17 @@ std::optional<LinesOfCode> Pos::getCodeLines() const
         return std::nullopt;
 
     if (auto source = getSource()) {
-
+        LinesIterator lines(*source), end;
-        std::istringstream iss(*source);
-        // count the newlines.
-        int count = 0;
-        std::string curLine;
-        int pl = line - 1;
-
         LinesOfCode loc;
 
-        do {
+        if (line > 1)
-            std::getline(iss, curLine);
+            std::advance(lines, line - 2);
-            ++count;
+        if (lines != end && line > 1)
-            if (count < pl)
+            loc.prevLineOfCode = *lines++;
-                ;
+        if (lines != end)
-            else if (count == pl) {
+            loc.errLineOfCode = *lines++;
-                loc.prevLineOfCode = curLine;
+        if (lines != end)
-            } else if (count == pl + 1) {
+            loc.nextLineOfCode = *lines++;
-                loc.errLineOfCode = curLine;
-            } else if (count == pl + 2) {
-                loc.nextLineOfCode = curLine;
-                break;
-            }
-
-            if (!iss.good())
-                break;
-        } while (true);
 
         return loc;
     }
@@ -109,4 +94,26 @@ std::ostream & operator<<(std::ostream & str, const Pos & pos)
     return str;
 }
 
+void Pos::LinesIterator::bump(bool atFirst)
+{
+    if (!atFirst) {
+        pastEnd = input.empty();
+        if (!input.empty() && input[0] == '\r')
+            input.remove_prefix(1);
+        if (!input.empty() && input[0] == '\n')
+            input.remove_prefix(1);
+    }
+
+    // nix line endings are not only \n as eg std::getline assumes, but also
+    // \r\n **and \r alone**. not treating them all the same causes error
+    // reports to not match with line numbers as the parser expects them.
+    auto eol = input.find_first_of("\r\n");
+
+    if (eol > input.size())
+        eol = input.size();
+
+    curLine = input.substr(0, eol);
+    input.remove_prefix(eol);
+}
+
 }

src/libutil/position.hh

@@ -67,6 +67,48 @@ struct Pos
     bool operator==(const Pos & rhs) const = default;
     bool operator!=(const Pos & rhs) const = default;
     bool operator<(const Pos & rhs) const;
+
+    struct LinesIterator {
+        using difference_type = size_t;
+        using value_type = std::string_view;
+        using reference = const std::string_view &;
+        using pointer = const std::string_view *;
+        using iterator_category = std::input_iterator_tag;
+
+        LinesIterator(): pastEnd(true) {}
+        explicit LinesIterator(std::string_view input): input(input), pastEnd(input.empty()) {
+            if (!pastEnd)
+                bump(true);
+        }
+
+        LinesIterator & operator++() {
+            bump(false);
+            return *this;
+        }
+        LinesIterator operator++(int) {
+            auto result = *this;
+            ++*this;
+            return result;
+        }
+
+        reference operator*() const { return curLine; }
+        pointer operator->() const { return &curLine; }
+
+        bool operator!=(const LinesIterator & other) const {
+            return !(*this == other);
+        }
+        bool operator==(const LinesIterator & other) const {
+            return (pastEnd && other.pastEnd)
+                || (std::forward_as_tuple(input.size(), input.data())
+                    == std::forward_as_tuple(other.input.size(), other.input.data()));
+        }
+
+    private:
+        std::string_view input, curLine;
+        bool pastEnd = false;
+
+        void bump(bool atFirst);
+    };
 };
 
 std::ostream & operator<<(std::ostream & str, const Pos & pos);

src/libutil/posix-source-accessor.cc

@@ -85,16 +85,20 @@ bool PosixSourceAccessor::pathExists(const CanonPath & path)
 
 std::optional<struct stat> PosixSourceAccessor::cachedLstat(const CanonPath & path)
 {
-    static Sync<std::unordered_map<CanonPath, std::optional<struct stat>>> _cache;
+    static Sync<std::unordered_map<Path, std::optional<struct stat>>> _cache;
+
+    // Note: we convert std::filesystem::path to Path because the
+    // former is not hashable on libc++.
+    Path absPath = makeAbsPath(path);
 
     {
         auto cache(_cache.lock());
-        auto i = cache->find(path);
+        auto i = cache->find(absPath);
         if (i != cache->end()) return i->second;
     }
 
     std::optional<struct stat> st{std::in_place};
-    if (::lstat(makeAbsPath(path).c_str(), &*st)) {
+    if (::lstat(absPath.c_str(), &*st)) {
         if (errno == ENOENT || errno == ENOTDIR)
             st.reset();
         else
@@ -103,7 +107,7 @@ std::optional<struct stat> PosixSourceAccessor::cachedLstat(const CanonPath & pa
 
     auto cache(_cache.lock());
     if (cache->size() >= 16384) cache->clear();
-    cache->emplace(path, st);
+    cache->emplace(absPath, st);
 
     return st;
 }

src/libutil/util.cc

@@ -9,6 +9,10 @@
 
 #include <sodium.h>
 
+#ifdef NDEBUG
+#error "Nix may not be built with assertions disabled (i.e. with -DNDEBUG)."
+#endif
+
 namespace nix {
 
 void initLibUtil() {

src/nix/copy.md

@@ -11,6 +11,12 @@ R""(
   Note the `file://` - without this, the destination is a chroot
   store, not a binary cache.
 
+* Copy all store paths from a local binary cache in `/tmp/cache` to the local store:
+
+  ```console
+  # nix copy --all --from file:///tmp/cache
+  ```
+
 * Copy the entire current NixOS system closure to another machine via
   SSH:
 

src/nix/eval.cc

@@ -120,8 +120,17 @@ struct CmdEval : MixJSON, InstallableValueCommand, MixReadOnlyOption
         }
 
         else {
-            state->forceValueDeep(*v);
+            logger->cout(
-            logger->cout("%s", ValuePrinter(*state, *v, PrintOptions { .force = true }));
+                "%s",
+                ValuePrinter(
+                    *state,
+                    *v,
+                    PrintOptions {
+                        .force = true,
+                        .derivationPaths = true
+                    }
+                )
+            );
         }
     }
 };

src/nix/flake.cc

@@ -88,17 +88,19 @@ public:
         expectArgs({
             .label="inputs",
             .optional=true,
-            .handler={[&](std::string inputToUpdate){
+            .handler={[&](std::vector<std::string> inputsToUpdate){
-                InputPath inputPath;
+                for (auto inputToUpdate : inputsToUpdate) {
-                try {
+                    InputPath inputPath;
-                    inputPath = flake::parseInputPath(inputToUpdate);
+                    try {
-                } catch (Error & e) {
+                        inputPath = flake::parseInputPath(inputToUpdate);
-                    warn("Invalid flake input '%s'. To update a specific flake, use 'nix flake update --flake %s' instead.", inputToUpdate, inputToUpdate);
+                    } catch (Error & e) {
-                    throw e;
+                        warn("Invalid flake input '%s'. To update a specific flake, use 'nix flake update --flake %s' instead.", inputToUpdate, inputToUpdate);
+                        throw e;
+                    }
+                    if (lockFlags.inputUpdates.contains(inputPath))
+                        warn("Input '%s' was specified multiple times. You may have done this by accident.");
+                    lockFlags.inputUpdates.insert(inputPath);
                 }
-                if (lockFlags.inputUpdates.contains(inputPath))
-                    warn("Input '%s' was specified multiple times. You may have done this by accident.");
-                lockFlags.inputUpdates.insert(inputPath);
             }},
             .completer = {[&](AddCompletions & completions, size_t, std::string_view prefix) {
                 completeFlakeInputPath(completions, getEvalState(), getFlakeRefsForCompletion(), prefix);
@@ -205,6 +207,9 @@ struct CmdFlakeMetadata : FlakeCommand, MixJSON
         auto lockedFlake = lockFlake();
         auto & flake = lockedFlake.flake;
 
+        // Currently, all flakes are in the Nix store via the rootFS accessor.
+        auto storePath = store->printStorePath(store->toStorePath(flake.path.path.abs()).first);
+
         if (json) {
             nlohmann::json j;
             if (flake.description)
@@ -214,6 +219,8 @@ struct CmdFlakeMetadata : FlakeCommand, MixJSON
             j["resolvedUrl"] = flake.resolvedRef.to_string();
             j["resolved"] = fetchers::attrsToJSON(flake.resolvedRef.toAttrs());
             j["url"] = flake.lockedRef.to_string(); // FIXME: rename to lockedUrl
+            // "locked" is a misnomer - this is the result of the
+            // attempt to lock.
             j["locked"] = fetchers::attrsToJSON(flake.lockedRef.toAttrs());
             if (auto rev = flake.lockedRef.input.getRev())
                 j["revision"] = rev->to_string(HashFormat::Base16, false);
@@ -223,23 +230,24 @@ struct CmdFlakeMetadata : FlakeCommand, MixJSON
                 j["revCount"] = *revCount;
             if (auto lastModified = flake.lockedRef.input.getLastModified())
                 j["lastModified"] = *lastModified;
-            j["path"] = store->printStorePath(flake.storePath);
+            j["path"] = storePath;
             j["locks"] = lockedFlake.lockFile.toJSON().first;
             logger->cout("%s", j.dump());
         } else {
             logger->cout(
                 ANSI_BOLD "Resolved URL:" ANSI_NORMAL "  %s",
                 flake.resolvedRef.to_string());
-            logger->cout(
+            if (flake.lockedRef.input.isLocked())
-                ANSI_BOLD "Locked URL:" ANSI_NORMAL "    %s",
+                logger->cout(
-                flake.lockedRef.to_string());
+                    ANSI_BOLD "Locked URL:" ANSI_NORMAL "    %s",
+                    flake.lockedRef.to_string());
             if (flake.description)
                 logger->cout(
                     ANSI_BOLD "Description:" ANSI_NORMAL "   %s",
                     *flake.description);
             logger->cout(
                 ANSI_BOLD "Path:" ANSI_NORMAL "          %s",
-                store->printStorePath(flake.storePath));
+                storePath);
             if (auto rev = flake.lockedRef.input.getRev())
                 logger->cout(
                     ANSI_BOLD "Revision:" ANSI_NORMAL "      %s",
@@ -474,6 +482,8 @@ struct CmdFlakeCheck : FlakeCommand
 
         checkHydraJobs = [&](const std::string & attrPath, Value & v, const PosIdx pos) {
             try {
+                Activity act(*logger, lvlInfo, actUnknown,
+                    fmt("checking Hydra job '%s'", attrPath));
                 state->forceAttrs(v, pos, "");
 
                 if (state->isDerivation(v))
@@ -1031,7 +1041,9 @@ struct CmdFlakeArchive : FlakeCommand, MixJSON, MixDryRun
 
         StorePathSet sources;
 
-        sources.insert(flake.flake.storePath);
+        auto storePath = store->toStorePath(flake.flake.path.path.abs()).first;
+
+        sources.insert(storePath);
 
         // FIXME: use graph output, handle cycles.
         std::function<nlohmann::json(const Node & node)> traverse;
@@ -1043,7 +1055,7 @@ struct CmdFlakeArchive : FlakeCommand, MixJSON, MixDryRun
                     auto storePath =
                         dryRun
                         ? (*inputNode)->lockedRef.input.computeStorePath(*store)
-                        : (*inputNode)->lockedRef.input.fetch(store).first;
+                        : (*inputNode)->lockedRef.input.fetchToStore(store).first;
                     if (json) {
                         auto& jsonObj3 = jsonObj2[inputName];
                         jsonObj3["path"] = store->printStorePath(storePath);
@@ -1060,7 +1072,7 @@ struct CmdFlakeArchive : FlakeCommand, MixJSON, MixDryRun
 
         if (json) {
             nlohmann::json jsonRoot = {
-                {"path", store->printStorePath(flake.flake.storePath)},
+                {"path", store->printStorePath(storePath)},
                 {"inputs", traverse(*flake.lockFile.root)},
             };
             logger->cout("%s", jsonRoot);

src/nix/profile-remove.md

@@ -11,9 +11,16 @@ R""(
 * Remove all packages:
 
   ```console
-  # nix profile remove '.*'
+  # nix profile remove --all
   ```
 
+* Remove packages by regular expression:
+
+  ```console
+  # nix profile remove --regex '.*vim.*'
+  ```
+
+
 * Remove a package by store path:
 
   ```console

src/nix/profile-upgrade.md

@@ -6,7 +6,7 @@ R""(
   reference:
 
   ```console
-  # nix profile upgrade '.*'
+  # nix profile upgrade --all
   ```
 
 * Upgrade a specific package by name:
@@ -15,6 +15,12 @@ R""(
   # nix profile upgrade hello
   ```
 
+* Upgrade all packages that include 'vim' in their name:
+
+  ```console
+  # nix profile upgrade --regex '.*vim.*'
+  ```
+
 # Description
 
 This command upgrades a previously installed package in a Nix profile,

src/nix/profile.cc

@@ -222,6 +222,8 @@ struct ProfileManifest
             es[name] = obj;
         }
         nlohmann::json json;
+        // Only upgrade with great care as changing it can break fresh installs
+        // like in https://github.com/NixOS/nix/issues/10109
         json["version"] = 3;
         json["elements"] = es;
         return json;
@@ -477,55 +479,151 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
     }
 };
 
-class MixProfileElementMatchers : virtual Args
+struct Matcher
 {
-    std::vector<std::string> _matchers;
+    virtual ~Matcher() { }
+    virtual std::string getTitle() = 0;
+    virtual bool matches(const std::string & name, const ProfileElement & element) = 0;
+};
+
+struct RegexMatcher final : public Matcher
+{
+    std::regex regex;
+    std::string pattern;
+
+    RegexMatcher(const std::string & pattern) : regex(pattern, std::regex::extended | std::regex::icase), pattern(pattern)
+    { }
+
+    std::string getTitle() override
+    {
+        return fmt("Regex '%s'", pattern);
+    }
+
+    bool matches(const std::string & name, const ProfileElement & element) override
+    {
+        return std::regex_match(element.identifier(), regex);
+    }
+};
+
+struct StorePathMatcher final : public Matcher
+{
+    nix::StorePath storePath;
+
+    StorePathMatcher(const nix::StorePath & storePath) : storePath(storePath)
+    { }
+
+    std::string getTitle() override
+    {
+        return fmt("Store path '%s'", storePath.to_string());
+    }
+
+    bool matches(const std::string & name, const ProfileElement & element) override
+    {
+        return element.storePaths.count(storePath);
+    }
+};
+
+struct NameMatcher final : public Matcher
+{
+    std::string name;
+
+    NameMatcher(const std::string & name) : name(name)
+    { }
+
+    std::string getTitle() override
+    {
+        return fmt("Package name '%s'", name);
+    }
+
+    bool matches(const std::string & name, const ProfileElement & element) override
+    {
+        return name == this->name;
+    }
+};
+
+struct AllMatcher final : public Matcher
+{
+    std::string getTitle() override
+    {
+        return "--all";
+    }
+
+    bool matches(const std::string & name, const ProfileElement & element) override
+    {
+        return true;
+    }
+};
+
+AllMatcher all;
+
+class MixProfileElementMatchers : virtual Args, virtual StoreCommand
+{
+    std::vector<ref<Matcher>> _matchers;
 
 public:
 
     MixProfileElementMatchers()
     {
-        expectArgs("elements", &_matchers);
+        addFlag({
+            .longName = "all",
+            .description = "Match all packages in the profile.",
+            .handler = {[this]() {
+                _matchers.push_back(ref<AllMatcher>(std::shared_ptr<AllMatcher>(&all, [](AllMatcher*) {})));
+            }},
+        });
+        addFlag({
+            .longName = "regex",
+            .description = "A regular expression to match one or more packages in the profile.",
+            .labels = {"pattern"},
+            .handler = {[this](std::string arg) {
+                _matchers.push_back(make_ref<RegexMatcher>(arg));
+            }},
+        });
+        expectArgs({
+            .label = "elements",
+            .optional = true,
+            .handler = {[this](std::vector<std::string> args) {
+                for (auto & arg : args) {
+                    if (auto n = string2Int<size_t>(arg)) {
+                        throw Error("'nix profile' no longer supports indices ('%d')", *n);
+                    } else if (getStore()->isStorePath(arg)) {
+                        _matchers.push_back(make_ref<StorePathMatcher>(getStore()->parseStorePath(arg)));
+                    } else {
+                        _matchers.push_back(make_ref<NameMatcher>(arg));
+                    }
+                }
+            }}
+        });
     }
 
-    struct RegexPattern {
+    std::set<std::string> getMatchingElementNames(ProfileManifest & manifest) {
-        std::string pattern;
+        if (_matchers.empty()) {
-        std::regex  reg;
+            throw UsageError("No packages specified.");
-    };
-    typedef std::variant<Path, RegexPattern> Matcher;
-
-    std::vector<Matcher> getMatchers(ref<Store> store)
-    {
-        std::vector<Matcher> res;
-
-        for (auto & s : _matchers) {
-            if (auto n = string2Int<size_t>(s))
-                throw Error("'nix profile' no longer supports indices ('%d')", *n);
-            else if (store->isStorePath(s))
-                res.push_back(s);
-            else
-                res.push_back(RegexPattern{s,std::regex(s, std::regex::extended | std::regex::icase)});
         }
 
-        return res;
+        if (std::find_if(_matchers.begin(), _matchers.end(), [](const ref<Matcher> & m) { return m.dynamic_pointer_cast<AllMatcher>(); }) != _matchers.end() && _matchers.size() > 1) {
-    }
+            throw UsageError("--all cannot be used with package names or regular expressions.");
+        }
 
-    bool matches(
+        if (manifest.elements.empty()) {
-        const Store & store,
+            warn("There are no packages in the profile.");
-        const std::string & name,
+            return {};
-        const ProfileElement & element,
+        }
-        const std::vector<Matcher> & matchers)
+
-    {
+        std::set<std::string> result;
-        for (auto & matcher : matchers) {
+        for (auto & matcher : _matchers) {
-            if (auto path = std::get_if<Path>(&matcher)) {
+            bool foundMatch = false;
-                if (element.storePaths.count(store.parseStorePath(*path))) return true;
+            for (auto & [name, element] : manifest.elements) {
-            } else if (auto regex = std::get_if<RegexPattern>(&matcher)) {
+                if (matcher->matches(name, element)) {
-                if (std::regex_match(name, regex->reg))
+                    result.insert(name);
-                    return true;
+                    foundMatch = true;
+                }
+            }
+            if (!foundMatch) {
+                warn("%s does not match any packages in the profile.", matcher->getTitle());
             }
         }
-
+        return result;
-        return false;
     }
 };
 
@@ -547,16 +645,19 @@ struct CmdProfileRemove : virtual EvalCommand, MixDefaultProfile, MixProfileElem
     {
         ProfileManifest oldManifest(*getEvalState(), *profile);
 
-        auto matchers = getMatchers(store);
+        ProfileManifest newManifest = oldManifest;
 
-        ProfileManifest newManifest;
+        auto matchingElementNames = getMatchingElementNames(oldManifest);
 
-        for (auto & [name, element] : oldManifest.elements) {
+        if (matchingElementNames.empty()) {
-            if (!matches(*store, name, element, matchers)) {
+            warn ("No packages to remove. Use 'nix profile list' to see the current profile.");
-                newManifest.elements.insert_or_assign(name, std::move(element));
+            return;
-            } else {
+        }
-                notice("removing '%s'", element.identifier());
+
-            }
+        for (auto & name : matchingElementNames) {
+            auto & element = oldManifest.elements[name];
+            notice("removing '%s'", element.identifier());
+            newManifest.elements.erase(name);
         }
 
         auto removedCount = oldManifest.elements.size() - newManifest.elements.size();
@@ -564,16 +665,6 @@ struct CmdProfileRemove : virtual EvalCommand, MixDefaultProfile, MixProfileElem
             removedCount,
             newManifest.elements.size());
 
-        if (removedCount == 0) {
-            for (auto matcher: matchers) {
-                if (const Path * path = std::get_if<Path>(&matcher)) {
-                    warn("'%s' does not match any paths", *path);
-                } else if (const RegexPattern * regex = std::get_if<RegexPattern>(&matcher)) {
-                    warn("'%s' does not match any packages", regex->pattern);
-                }
-            }
-            warn ("Use 'nix profile list' to see the current profile.");
-        }
         updateProfile(newManifest.build(store));
     }
 };
@@ -596,20 +687,20 @@ struct CmdProfileUpgrade : virtual SourceExprCommand, MixDefaultProfile, MixProf
     {
         ProfileManifest manifest(*getEvalState(), *profile);
 
-        auto matchers = getMatchers(store);
-
         Installables installables;
         std::vector<ProfileElement *> elems;
 
-        auto matchedCount = 0;
         auto upgradedCount = 0;
 
-        for (auto & [name, element] : manifest.elements) {
+        auto matchingElementNames = getMatchingElementNames(manifest);
-            if (!matches(*store, name, element, matchers)) {
-                continue;
-            }
 
-            matchedCount++;
+        if (matchingElementNames.empty()) {
+            warn("No packages to upgrade. Use 'nix profile list' to see the current profile.");
+            return;
+        }
+
+        for (auto & name : matchingElementNames) {
+            auto & element = manifest.elements[name];
 
             if (!element.source) {
                 warn(
@@ -648,7 +739,9 @@ struct CmdProfileUpgrade : virtual SourceExprCommand, MixDefaultProfile, MixProf
             assert(infop);
             auto & info = *infop;
 
-            if (element.source->lockedRef == info.flake.lockedRef) continue;
+            if (info.flake.lockedRef.input.isLocked()
+                && element.source->lockedRef == info.flake.lockedRef)
+                continue;
 
             printInfo("upgrading '%s' from flake '%s' to '%s'",
                 element.source->attrPath, element.source->lockedRef, info.flake.lockedRef);
@@ -665,18 +758,8 @@ struct CmdProfileUpgrade : virtual SourceExprCommand, MixDefaultProfile, MixProf
         }
 
         if (upgradedCount == 0) {
-            if (matchedCount == 0) {
+            warn("Found some packages but none of them could be upgraded.");
-                for (auto & matcher : matchers) {
+            return;
-                    if (const Path * path = std::get_if<Path>(&matcher)) {
-                        warn("'%s' does not match any paths", *path);
-                    } else if (const RegexPattern * regex = std::get_if<RegexPattern>(&matcher)) {
-                        warn("'%s' does not match any packages", regex->pattern);
-                    }
-                }
-            } else {
-                warn("Found some packages but none of them could be upgraded.");
-            }
-            warn ("Use 'nix profile list' to see the current profile.");
         }
 
         auto builtPaths = builtPathsPerInstallable(

src/nix/registry-pin.md

@@ -15,10 +15,10 @@ R""(
   user   flake:nixpkgs github:NixOS/nixpkgs/925b70cd964ceaedee26fde9b19cc4c4f081196a
   ```
 
-  and `nix flake info` will say:
+  and `nix flake metadata` will say:
 
   ```console
-  # nix flake info nixpkgs
+  # nix flake metadata nixpkgs
   Resolved URL:  github:NixOS/nixpkgs/925b70cd964ceaedee26fde9b19cc4c4f081196a
   Locked URL:    github:NixOS/nixpkgs/925b70cd964ceaedee26fde9b19cc4c4f081196a
   …

src/nix/registry.cc

@@ -188,7 +188,9 @@ struct CmdRegistryPin : RegistryCommand, EvalCommand
         auto ref = parseFlakeRef(url);
         auto lockedRef = parseFlakeRef(locked);
         registry->remove(ref.input);
-        auto [tree, resolved] = lockedRef.resolve(store).input.fetch(store);
+        auto resolved = lockedRef.resolve(store).input.getAccessor(store).second;
+        if (!resolved.isLocked())
+            warn("flake '%s' is not locked", resolved.to_string());
         fetchers::Attrs extraAttrs;
         if (ref.subdir != "") extraAttrs["dir"] = ref.subdir;
         registry->add(ref.input, resolved, extraAttrs);

tests/functional/common/vars-and-functions.sh.in

@@ -216,6 +216,17 @@ expectStderr() {
     return 0
 }
 
+# Run a command and check whether the stderr matches stdin.
+# Show a diff when output does not match.
+# Usage:
+#
+#   assertStderr nix profile remove nothing << EOF
+#   error: This error is expected
+#   EOF
+assertStderr() {
+    diff -u /dev/stdin <($@ 2>/dev/null 2>&1)
+}
+
 needLocalStore() {
   if [[ "$NIX_REMOTE" == "daemon" ]]; then
     skipTest "Can’t run through the daemon ($1)"

tests/functional/eval.sh

@@ -41,3 +41,14 @@ mkdir -p $TEST_ROOT/xyzzy $TEST_ROOT/foo
 ln -sfn ../xyzzy $TEST_ROOT/foo/bar
 printf 123 > $TEST_ROOT/xyzzy/default.nix
 [[ $(nix eval --impure --expr "import $TEST_ROOT/foo/bar") = 123 ]]
+
+# Test --arg-from-file.
+[[ "$(nix eval --raw --arg-from-file foo config.nix --expr '{ foo }: { inherit foo; }' foo)" = "$(cat config.nix)" ]]
+
+# Check that special(-ish) files are drained.
+if [[ -e /proc/version ]]; then
+    [[ "$(nix eval --raw --arg-from-file foo /proc/version --expr '{ foo }: { inherit foo; }' foo)" = "$(cat /proc/version)" ]]
+fi
+
+# Test --arg-from-stdin.
+[[ "$(echo bla | nix eval --raw --arg-from-stdin foo --expr '{ foo }: { inherit foo; }' foo)" = bla ]]

tests/functional/flakes/flakes.sh

@@ -564,6 +564,16 @@ nix flake lock "$flake3Dir"
 nix flake update flake2/flake1 --flake "$flake3Dir"
 [[ $(jq -r .nodes.flake1_2.locked.rev "$flake3Dir/flake.lock") =~ $hash2 ]]
 
+# Test updating multiple inputs.
+nix flake lock "$flake3Dir" --override-input flake1 flake1/master/$hash1
+nix flake lock "$flake3Dir" --override-input flake2/flake1 flake1/master/$hash1
+[[ $(jq -r .nodes.flake1.locked.rev "$flake3Dir/flake.lock") =~ $hash1 ]]
+[[ $(jq -r .nodes.flake1_2.locked.rev "$flake3Dir/flake.lock") =~ $hash1 ]]
+
+nix flake update flake1 flake2/flake1 --flake "$flake3Dir"
+[[ $(jq -r .nodes.flake1.locked.rev "$flake3Dir/flake.lock") =~ $hash2 ]]
+[[ $(jq -r .nodes.flake1_2.locked.rev "$flake3Dir/flake.lock") =~ $hash2 ]]
+
 # Test 'nix flake metadata --json'.
 nix flake metadata "$flake3Dir" --json | jq .
 

tests/functional/flakes/search-root.sh

@@ -22,7 +22,7 @@ mkdir subdir
 pushd subdir
 
 success=("" . .# .#test ../subdir ../subdir#test "$PWD")
-failure=("path:$PWD")
+failure=("path:$PWD" "../simple.nix")
 
 for i in "${success[@]}"; do
     nix build $i || fail "flake should be found by searching up directories"

tests/functional/git-hashing/simple.sh

@@ -56,3 +56,12 @@ echo Run Hello World! > $TEST_ROOT/dummy3/dir/executable
 path3=$(nix store add --mode git --hash-algo sha1 $TEST_ROOT/dummy3)
 hash3=$(nix-store -q --hash $path3)
 test "$hash3" = "sha256:08y3nm3mvn9qvskqnf13lfgax5lh73krxz4fcjd5cp202ggpw9nv"
+
+rm -rf $TEST_ROOT/dummy3
+mkdir -p $TEST_ROOT/dummy3
+mkdir -p $TEST_ROOT/dummy3/dir
+touch $TEST_ROOT/dummy3/dir/file
+ln -s './hello/world.txt' $TEST_ROOT/dummy3/dir/symlink
+path3=$(nix store add --mode git --hash-algo sha1 $TEST_ROOT/dummy3)
+hash3=$(nix-store -q --hash $path3)
+test "$hash3" = "sha256:1dwazas8irzpar89s8k2bnp72imfw7kgg4aflhhsfnicg8h428f3"

tests/functional/help.sh

@@ -0,0 +1,69 @@
+source common.sh
+
+clearStore
+
+# test help output
+
+nix-build --help
+nix-shell --help
+
+nix-env --help
+nix-env --install --help
+nix-env --upgrade --help
+nix-env --uninstall --help
+nix-env --set --help
+nix-env --set-flag --help
+nix-env --query --help
+nix-env --switch-profile --help
+nix-env --list-generations --help
+nix-env --delete-generations --help
+nix-env --switch-generation --help
+nix-env --rollback --help
+
+nix-store --help
+nix-store --realise --help
+nix-store --serve --help
+nix-store --gc --help
+nix-store --delete --help
+nix-store --query --help
+nix-store --add --help
+nix-store --add-fixed --help
+nix-store --verify --help
+nix-store --verify-path --help
+nix-store --repair-path --help
+nix-store --dump --help
+nix-store --restore --help
+nix-store --export --help
+nix-store --import --help
+nix-store --optimise --help
+nix-store --read-log --help
+nix-store --dump-db --help
+nix-store --load-db --help
+nix-store --print-env --help
+nix-store --generate-binary-cache-key --help
+
+nix-channel --help
+nix-collect-garbage --help
+nix-copy-closure --help
+nix-daemon --help
+nix-hash --help
+nix-instantiate --help
+nix-prefetch-url --help
+
+function subcommands() {
+  jq -r '
+def recurse($prefix):
+    to_entries[] |
+    ($prefix + [.key]) as $newPrefix |
+    (if .value | has("commands") then
+      ($newPrefix, (.value.commands | recurse($newPrefix)))
+    else
+      $newPrefix
+    end);
+.args.commands | recurse([]) | join(" ")
+'
+}
+
+nix __dump-cli | subcommands | while IFS= read -r cmd; do
+    nix $cmd --help
+done

tests/functional/lang/eval-fail-eol-1.err.exp

@@ -0,0 +1,6 @@
+error: undefined variable 'invalid'
+       at /pwd/lang/eval-fail-eol-1.nix:2:1:
+            1| # foo
+            2| invalid
+             | ^
+            3| # bar

tests/functional/lang/eval-fail-eol-1.nix

@@ -0,0 +1,3 @@
+# foo
+invalid
+# bar