Support specifying layered requirements in a single file

[jab]

I recently noticed #2679 -- awesome to see all the interest in that!

As long as we're thinking about enabling combining different requirements files for different platforms into a single, platform-independent lockfile, is there any interest in enabling you to specify additional requirements layers (e.g. for running tests, building docs, etc., which should be constrained by the base layer, in a single file as well?

Many projects end up with requirements file explosion due to layering even more often than due to platform differences. Enabling users to define their requirement layers in a single file would be a wonderful simplification.

[zanieb]

Hi! Have you seen PEP 735? I think that addresses what you're talking about. Right now we're only exposing a single group for development dependencies but we're watching that PEP as a possible standard we could use for specifying multiple groups. We're working on a lock file format (#3314) that is a single file. I'm not sure we'd extend locking of multiple groups to requirements.txt style files.

[jab]

Thanks for the heads up about PEP 735, and great you're already thinking along these lines!

Any solution enabling projects to maintain a single pair of files -- one for all the dependency group inputs, and one with the result of resolving those inputs -- would be a win. Using a standardized and more structured format than requirements.txt to accomplish that would be icing on the cake.

[zanieb]

Great to hear! Yeah we're planning on using the pyproject.toml for the declaration (with a tool.uv.sources extension for things like custom indexes per package that are not supported by the standard project.dependencies section) and a uv.lock with cross-platform resolutions of all of your extras and development dependencies. You can try some of it right now if you want, we'll be announcing more and writing new documentation soon though!

[zanieb]

I think #3347 can be used to track this request.