Without the change the eval fails as:

$ nix build --no-link -f. discourse.discourseAllPlugins.tests
error:
   … from call site
     at pkgs/servers/web-apps/discourse/default.nix:436:15:
      435|       ruby = rubyEnv.wrappedRuby;
      436|       tests = import ../../../../nixos/tests/discourse.nix {
         |               ^
      437|         inherit (stdenv) system;

   error: function 'anonymous lambda' called without required argument 'lib'
   at nixos/tests/discourse.nix:6:1:
        5|
        6| {
         | ^
        7|   package,

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/)
• Nixpkgs 25.11 Release Notes (or backporting 24.11 and 25.05 Nixpkgs Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
• NixOS 25.11 Release Notes (or backporting 24.11 and 25.05 NixOS Release notes)
  • (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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