update-python-libraries: migrate git revs to tag

[mweinelt]

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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[Atemu]

Not very familiar with this part of Nixpkgs but it looks sane to me at a glance.

[philiptaron]

I read the Python. 🐍

[mweinelt]

Hey, can we please give codeowners time to review and merge? Thank you.

[philiptaron]

Hey, can we please give codeowners time to review and merge? Thank you.

My apologies for jumping the metaphorical gun.

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/statistics-on-nixpkgs-prs-over-time/55916/14

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/statistics-on-nixpkgs-prs-over-time/55916/17

[natsukium]

Thanks for working on and reviewing this change!
I just found the context for this PR. I think it's fine.

[mweinelt]

Seeing this now, we should unquote and then not interpolate the version, when the prefix is empty.

[zowoq]

@mweinelt Seems this is blocking a lot of nixpkgs-update python packages updates, migrating the src to tag works but it then fails trying to eval src.rev in meta.changelog.

[Atemu]

That's a good time to stop doing that; you shouldn't assume anything about src other than that it's a path.

You might need to switch between rev and tag on updates or users may override src with anything they like.

Depending on src's internals feels like a layer violation to me.

[zowoq]

That's a good time to stop doing that; you shouldn't assume anything about src other than that it's a path.

The assumption is that meta evaluates, using the same method that is enforced by nixpkgs CI.

[Atemu]

Sorry, I what I wrote was ambiguous: To stop depending on src.tag in meta; specifically depending on any internal state of src at all.

You'd necessarily need to pass the tag to the "constructor" of src anyways, so simply re-use that same declaration for changelog instead.

[zowoq]

Perhaps what I wrote was also ambiguous or maybe we're just talking past each other: nixpkgs-update doesn't depend on src for meta. The issue is that sometimes the migration of a python package from rev to tag is incomplete.

[Atemu]

Yes and the cause of that is the layer violation I talked about; depending on an internal property of src. If that property changes, breakage occurs. Therefore, you should not depend on the internal property.

[zowoq]

Yeah, I think we're just talking past each other.

[mweinelt]

@mweinelt Seems this is blocking a lot of nixpkgs-update python packages updates, migrating the src to tag works but it then fails trying to eval src.rev in meta.changelog.

Thanks, I'll have a look in the next few days.

[mweinelt]

Not forgotten, but not so straightforward.