lib.options.mkPackageOption: use lib.showAttrPath

[MattSturgeon]

Make use of lib.showAttrPath instead of manually doing concatStringsSep ".".

This means edge-cases like . being included in an attr-name will be handled better.

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
    • nix-build lib/tests/release.nix
  • 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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[roberth]

The new behavior looks good to me. Could you add a test case for this new requirement?

[MattSturgeon]

Could you add a test case for this new requirement?

Sure, I can do that later. OTTOYH do you know where tests for mkPackageOption live?

[roberth]

Probably lib/tests/modules.sh, but we have one or two docs tests in lib/tests/misc.nix also.

[MattSturgeon]

Thanks.

I've amended the commit to add tests for the defaultText and example being attr-paths that contain non-identifier names.

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I also noticed several test cases were declared in declare-mkPackageOption.nix but not tested in modules.sh, so I've added a secondary commit to remedy that.

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One other theoretical edge-case I noticed is when name' (used in description) is derived from the last element in the name attr-path, this could potentially contain markdown syntax which ought to be escaped.

I don't necessarily want to address that in this PR, and we don't seem to have a lib.strings.escapeMD yet either.

In such cases, users can manually specify name and default separately, so this isn't a big deal.

[MattSturgeon]

@roberth are you able to review now that tests have been added?

[hsjobeki]

Looking lgtm to me. Since only the tests where missing @roberth, im merging this one.