pet: add bash and fish shell completions

[s3igo]

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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[acid-bong]

Nixpkgs manual has an example of using cross env when it's possible: https://nixos.org/manual/nixpkgs/unstable/#installshellfiles-installshellcompletion-exampleusage-guarded. Maybe use that?

[drupol]

Hello!

Welcome to the Nix project and thanks for the PR.

I added a minor comment.

Regarding the rest, I will check later if a more up to date way is available for the completions.

[drupol]

Remove this and use writableTmpDirAsHomeHook

[s3igo]

Nixpkgs manual has an example of using cross env when it's possible: https://nixos.org/manual/nixpkgs/unstable/#installshellfiles-installshellcompletion-exampleusage-guarded. Maybe use that?

Is it suggesting that using lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) as a guard is not idiomatic? I implemented it this way because similar approaches were taken in packages like Starship and Zellij.

[s3igo]

Nixpkgs manual has an example of using cross env when it's possible: https://nixos.org/manual/nixpkgs/unstable/#installshellfiles-installshellcompletion-exampleusage-guarded. Maybe use that?

Yes, this is precisely what I was looking for. When using this, there's no need to have a condition (lib.optionalString). If you could implement that preferred solution, it would be great.

As I'm still learning Nix, I'm confused about why this approach eliminates the need for lib.optionalString.
Could you please provide guidance on the implementation approach?

[drupol]

Nixpkgs manual has an example of using cross env when it's possible: https://nixos.org/manual/nixpkgs/unstable/#installshellfiles-installshellcompletion-exampleusage-guarded. Maybe use that?

Yes, this is precisely what I was looking for. When using this, there's no need to have a condition (lib.optionalString). If you could implement that preferred solution, it would be great.

As I'm still learning Nix, I'm confused about why this approach eliminates the need for lib.optionalString. Could you please provide guidance on the implementation approach?

Please ignore my last comment, I have been too quick reviewing this and my comment is wrong. What you did is fine and I'm going to merge it after my local nixpkgs-review is done.

[drupol]

nixpkgs-review result

Generated using nixpkgs-review.

Command: nixpkgs-review pr 399954

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x86_64-linux

✅ 1 package built:

• pet

[drupol]

Thank you ! Keep PRs coming :)