qt6: remove stdenv fully

[rhelmot]

Let's see what breaks. See #370781

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

---

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[emilazy]

Nothing will break in‐tree (anything that causes warnings can’t be part of the release jobset anyway), but it might break external users. We could probably get away with just making it a throw.

[rhelmot]

I think the thing I was seeing earlier was that the warnings were being triggered in-tree simply by accessing pkgsCross.x86_64-freebsd.qt6Packages.accounts-qt, so a throw would probably trip there too.

[K900]

That sounds wrong.

[rhelmot]

[+] ~/proj/nix/nixpkgs% nix-instantiate . -A pkgsCross.x86_64-freebsd.qt6Packages.accounts-qt                                                                                                                                                                                                        audrey@daisy [02:06:58 PM]
error:
       … while calling a functor (an attribute set with a '__functor' attribute)
         at /home/audrey/proj/nix/nixpkgs/lib/customisation.nix:306:7:
          305|     if missingArgs == { } then
          306|       makeOverridable f allArgs
             |       ^
          307|     # This needs to be an abort so it can't be caught with `builtins.tryEval`,

       … while evaluating a branch condition
         at /home/audrey/proj/nix/nixpkgs/lib/customisation.nix:173:7:
          172|       in
          173|       if isAttrs result then
             |       ^
          174|         result

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: Accessing the invalid property
[+] ~/proj/nix/nixpkgs% git diff                                                                                                                                                                                                                                                                     audrey@daisy [02:07:01 PM]
diff --git a/pkgs/top-level/qt6-packages.nix b/pkgs/top-level/qt6-packages.nix
index fd3606df0d75..f9a04d3d4e71 100644
--- a/pkgs/top-level/qt6-packages.nix
+++ b/pkgs/top-level/qt6-packages.nix
@@ -136,5 +136,5 @@ makeScopeWithSplicing' {
   });
 } // lib.optionalAttrs config.allowAliases {
   # when removing, don't forget to remove a workaround in `pkgs/kde/default.nix`
-  stdenv = lib.warn "qt6Packages.stdenv is deprecated. Use stdenv instead." stdenv; # Added for 25.05
+  stdenv = throw "Accessing the invalid property";
 }
[+] ~/proj/nix/nixpkgs% git status                                                                                                                                                                                                                                                                   audrey@daisy [02:07:08 PM]
On branch master
Your branch is up to date with 'upstream/master'.

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   pkgs/top-level/qt6-packages.nix

no changes added to commit (use "git add" and/or "git commit -a")
[+] ~/proj/nix/nixpkgs% git rev-parse HEAD                                                                                                                                                                                                                                                           audrey@daisy [02:07:13 PM]
7fdcf460054eb871ff8cc12aa1b7e7c561911d2e
[+] ~/proj/nix/nixpkgs%                                                                                                                                                                                                                                                                              audrey@daisy [02:07:13 PM]

Did you mean something else?

[K900]

I'm not saying it can't happen, I'm saying it shouldn't be. Something is clearly accessing it, but what? And why?

[rhelmot]

Full trace. It really looks like the stdenv is being pulled into the scope, but only for spliced package sets.

error:
       … from call site
         at /home/audrey/proj/nix/nixpkgs/pkgs/top-level/qt6-packages.nix:33:17:
           32|   # LIBRARIES
           33|   accounts-qt = callPackage ../development/libraries/accounts-qt { };
             |                 ^
           34|   appstream-qt = callPackage ../development/libraries/appstream/qt.nix { };
   … while calling 'callPackageWith'
     at /home/audrey/proj/nix/nixpkgs/lib/customisation.nix:240:19:
      239|   callPackageWith =
      240|     autoArgs: fn: args:
         |                   ^
      241|     let

   … while calling a functor (an attribute set with a '__functor' attribute)
     at /home/audrey/proj/nix/nixpkgs/lib/customisation.nix:306:7:
      305|     if missingArgs == { } then
      306|       makeOverridable f allArgs
         |       ^
      307|     # This needs to be an abort so it can't be caught with `builtins.tryEval`,

   … from call site
     at /home/audrey/proj/nix/nixpkgs/lib/trivial.nix:1000:7:
      999|     { # TODO: Should we add call-time "type" checking like built in?
     1000|       __functor = self: f;
         |       ^
     1001|       __functionArgs = args;

   … while calling anonymous lambda
     at /home/audrey/proj/nix/nixpkgs/lib/customisation.nix:161:7:
      160|     mirrorArgs (
      161|       origArgs:
         |       ^
      162|       let

   … while evaluating a branch condition
     at /home/audrey/proj/nix/nixpkgs/lib/customisation.nix:173:7:
      172|       in
      173|       if isAttrs result then
         |       ^
      174|         result

   … while calling the 'isAttrs' builtin
     at /home/audrey/proj/nix/nixpkgs/lib/customisation.nix:173:10:
      172|       in
      173|       if isAttrs result then
         |          ^
      174|         result

   … from call site
     at /home/audrey/proj/nix/nixpkgs/lib/customisation.nix:163:18:
      162|       let
      163|         result = f origArgs;
         |                  ^
      164|

   … while calling anonymous lambda
     at /home/audrey/proj/nix/nixpkgs/pkgs/development/libraries/accounts-qt/default.nix:1:1:
        1| {
         | ^
        2|   stdenv,

   … while evaluating a branch condition
     at /home/audrey/proj/nix/nixpkgs/pkgs/top-level/splice.nix:73:11:
       72|             # on to splice them together.
       73|           if lib.isDerivation defaultValue then augmentedValue // spliceReal {
         |           ^
       74|             pkgsBuildBuild = tryGetOutputs valueBuildBuild;

   … from call site
     at /home/audrey/proj/nix/nixpkgs/pkgs/top-level/splice.nix:73:14:
       72|             # on to splice them together.
       73|           if lib.isDerivation defaultValue then augmentedValue // spliceReal {
         |              ^
       74|             pkgsBuildBuild = tryGetOutputs valueBuildBuild;

   … while calling 'isDerivation'
     at /home/audrey/proj/nix/nixpkgs/lib/attrsets.nix:1282:5:
     1281|   isDerivation =
     1282|     value: value.type or null == "derivation";
         |     ^
     1283|

   … while evaluating the attribute 'stdenv'
     at /home/audrey/proj/nix/nixpkgs/pkgs/top-level/qt6-packages.nix:139:3:
      138|   # when removing, don't forget to remove a workaround in `pkgs/kde/default.nix`
      139|   stdenv = throw "Accessing the invalid property";
         |   ^
      140| }

   … while calling the 'throw' builtin
     at /home/audrey/proj/nix/nixpkgs/pkgs/top-level/qt6-packages.nix:139:12:
      138|   # when removing, don't forget to remove a workaround in `pkgs/kde/default.nix`
      139|   stdenv = throw "Accessing the invalid property";
         |            ^
      140| }

   error: Accessing the invalid property

[K900]

This really feels like something we should try and root cause.

[rhelmot]

Tagging @Ericson2314 as the only one I've ever seen be able to wrangle splicing bullshit of this magnitude 🙏

[rhelmot]

Actually, this looks extremely straightforward. Splicing seems to be implemented such that it just re-crawls the package tree from the root in order to generate the spliced set, completely without regard for any sort of subscoping, so the fact that pkgs.qt6Packages.stdenv is accessible means that it ends up accessible as pkgsCross.x86_64-freebsd.qt6Packages.stdenv. Then, generateSplicesForMkScope works by simply crawling the spliced root package sets, so when you say generateSplicesForMkScope "qt6Packages" it grabs you something that has the stdenv attribute, even though it was not part of the call to mkScopeWithSplicing'.

So... the fix is somewhat nontrivial. We can either do something radical in generateSplicesForMkScope which attempts to filter out things that aren't in the original, somehow, or we can do that filter on the result of it.

[K900]

Oof. I guess we can just do this then.