Summary

When experimenting with --resolution=lowest for astropy's complete dependency graph, I hit a diabolical edge case, where astropy has an optional dependency on asdf-astropy>=0.3, which itself requires astropy>=5.0.4 (astropy's current version number is in the 8.0.0dev+...). Apparently, uv fails to recognize that astropy is the package being resolved for, and it attempts to build v5.0.4 from source. This would already be a waste of time even if it worked, but it doesn't, making it harder to ignore.

example logs
relevant excerpt :

Building astropy==5.0.4
  × Failed to download and build `astropy==5.0.4`
  ├─▶ Failed to resolve requirements from `build-system.requires`
  ├─▶ No solution found when resolving: `setuptools`, `setuptools-scm>=6.2`,
  │   `wheel`, `cython==0.29.22`, `markupsafe==2.0.1`, `jinja2==3.0.3`,
  │   `oldest-supported-numpy`, `extension-helpers`
  ╰─▶ Because markupsafe==2.0.1 has no usable wheels and you require
      markupsafe==2.0.1, we can conclude that your requirements are
      unsatisfiable.

      hint: Wheels are required for `markupsafe` because building from
      source is disabled for `markupsafe` (i.e., with `--no-build-package
      markupsafe`)
  help: `astropy` (v5.0.4) was included because `asdf-astropy` (v0.3.0)
        depends on `astropy`

To add insult to injury, astropy's version number is dynamic...

I suppose at this point, the resolver cannot really be expected to do better than taking a bet and just assume that the version of astropy being built will satisfy the requirements. I think this would be fine as long as the assumption is checked after we're done building astropy.

I do note that there's a known workaround we can use by making astropy requiring a more recent version of asdf-astropy, but I think that's ultimately a hack, and only works because we end up downloading older versions of astropy that have matching wheels, so I'd be interested to see if there's a chance to resolve the root issue in uv instead.

Unfortunately I couldn't reproduce this locally on macOS (amr64), so I don't have the ability to reduce my reproducer yet.
Possibly related, but I don't think that's quite a duplicate: #16372

Platform

Seen on ubuntu ubuntu-24.04

Version

uv==0.9.11

Python version

3.11