refactor: nix flake for build and dev

[karlskewes]

Across the Cosmic repo's the flakes are all a little different and there are various PR's (e.g: #1993 #1374) .
If the maintainers are happy to have the files, then I think it would be great to align them.

I think basic criteria should be something like:

• no unnecessary dependencies where standard nix will do (e.g: crane, flake-utils for systems)
• no optional developer tools, e.g: bacon or similar
• nix build support
• nix develop support
• if possible: a canonical source for nixpkgs - is this practical?

Open to suggestions and alternatives.

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[MasterofNull]

Hi @karlskewes! I've been working on similar improvements and have some suggestions for this flake based on the nixpkgs cosmic-comp package:

Improvements I'd suggest:

1. Add inputs.nixpkgs.follows to rust-overlay to avoid duplicate nixpkgs evaluations
2. Add udev to buildInputs - required for device access (missing from current version)
3. Fix xrdb path - should be xorg.xrdb instead of bare xrdb
4. Use pname/version instead of just name (follows nixpkgs conventions)
5. Add separateDebugInfo = true for better debugging
6. Add makeFlags and dontCargoInstall = true to match how nixpkgs builds it
7. Add meta attribute with license, homepage, platforms, mainProgram
8. Add formatter output for nix fmt support
9. Add overlays.default for easy integration with other flakes
10. Enhance devShell with rust-analyzer and cargo-watch

I've implemented these changes in my fork: https://github.com/MasterofNull/cosmic-comp/tree/nix-flake

Feel free to cherry-pick any of these improvements, or I can submit them as suggestions/PR to your branch if that would help!

[karlskewes]

Hi @karlskewes! I've been working on similar improvements and have some suggestions for this flake based on the nixpkgs cosmic-comp package:

Improvements I'd suggest:

1. **Add `inputs.nixpkgs.follows`** to rust-overlay to avoid duplicate nixpkgs evaluations

2. **Add `udev` to buildInputs** - required for device access (missing from current version)

3. **Fix `xrdb` path** - should be `xorg.xrdb` instead of bare `xrdb`

4. **Use `pname`/`version`** instead of just `name` (follows nixpkgs conventions)

5. **Add `separateDebugInfo = true`** for better debugging

6. **Add `makeFlags` and `dontCargoInstall = true`** to match how nixpkgs builds it

7. **Add `meta` attribute** with license, homepage, platforms, mainProgram

8. **Add `formatter` output** for `nix fmt` support

9. **Add `overlays.default`** for easy integration with other flakes

10. **Enhance devShell** with rust-analyzer and cargo-watch

I've implemented these changes in my fork: https://github.com/MasterofNull/cosmic-comp/tree/nix-flake

Feel free to cherry-pick any of these improvements, or I can submit them as suggestions/PR to your branch if that would help!

Looks great, thank you. I cherry-picked the commit.
We're also still blocked on some dependency pinning:

• https://github.com/pop-os//cosmic-protocols double slash
• patch for cosmic-client-toolkit ... points to the same source`

Across the Cosmic repo's the flakes are all a little different and there are various PR's.
If the maintainers are happy to have the files, then I think it would be great to align them.

I think basic criteria would be something like:

• no unnecessary dependencies where standard nix will do (e.g: crane, flake-utils for systems)
• EDIT: no optional developer tools, e.g: bacon or similar
• nix build support
• nix develop support
• if possible: a canonical source for nixpkgs - is this practical?

[MasterofNull]

@karlskewes Thanks for cherry-picking the changes! I've pushed a follow-up fix for the double-slash issue you mentioned:

Fix: 85587d2e - Remove double slashes from cosmic-protocols patch URLs

The Cargo.toml patch section had typos:

- cosmic-protocols = { git = "https://github.com/pop-os//cosmic-protocols", branch = "main" }
+ cosmic-protocols = { git = "https://github.com/pop-os/cosmic-protocols", branch = "main" }

Feel free to cherry-pick this as well. The cosmic-client-toolkit pointing to cosmic-protocols repo appears intentional since it's part of that workspace.

[Elias-Graf]

Is there any particular reason we're not using crane anymore? Otherwise we could have also included checks:

checks = {
	formatting = craneLib.cargoFmt { inherit src; };
	linting = craneLib.cargoClippy {
		inherit src cargoArtifacts;
		cargoClippyExtraArgs = "--all-targets -- -D warnings";
	};
	testing = craneLib.cargoTest {
		inherit src cargoArtifacts;
	};
};

Anyway, it would be cool if this got merged, since the current flake is broken :). I was just about to make a PR updating it, but seeing this makes that redundant :D.

[karlskewes]

Is there any particular reason we're not using crane anymore? Otherwise we could have also included checks:

@Elias-Graf, I've updated the PR description based on another comment.
After seeing various flakes across the Cosmic repo's with various dependencies I thought to simplify it back to straight nix first.
I'm not a maintainer either and an alternative PR may be better :)

[karlskewes]

I've rebased this branch on 1.2.0 rather than an arbitrary master commit as I'm using it for development and it simplifies dependencies.

I'll rebase on master if/when there's appetite to merge.

Additionally have removed the redundant patch for cargo-protocols as it's already pinned in Cargo.toml.
This could/should be raised as a separate PR to master but per the current pinned protocols commit SHA.

[jacobgkau]

@karlskewes We can take a look at reviewing this to merge and closing the obsolete #1374 if you want to rebase this on master and remove any extraneous changes.

@nuwawa @faukah Feel free to provide any input. We'll assume you don't object to these changes if we don't hear back.

[karlskewes]

The patch seems unnecessary and breaks nix build due to // or duplicate source if remove //.
Set branch = "main" in further up on L24 and update Cargo.lock as well.

This commit could be a separate PR if preferred.

[karlskewes]

@karlskewes We can take a look at reviewing this to merge and closing the obsolete #1374 if you want to rebase this on master and remove any extraneous changes.

@nuwawa @faukah Feel free to provide any input. We'll assume you don't object to these changes if we don't hear back.

Thanks @jacobgkau, rebased on master and ready for review.
One change that's not Nix specific but I think is reasonable: #2219 (comment)

[jacobgkau]

Before, nix build, nix shell, and nix develop all failed with an error. On this branch, they all complete without error. So the Nix flake update seems like an improvement to me.

I also tested this through our normal build process and am not seeing any side effects from dropping the cosmic-protocols patch (but the engineering team can chime in if there's a reason that needs to still be in place).