pre-commit-uv does not work with python 3.14

[ssbarnea]

If you happen to try to run pre-commit-uv with python 3.14, you might see a confusing error like below:

E               AssertionError: BUG: expected environment for python to be healthy immediately after install, please open an issue describing your environment
E               
E               more info:
E               
E               virtualenv python version did not match created version:
E               - actual version: 3.14.0
E               - expected version: 3.14.0rc3

[gaborbernat]

This might be an upstream bug 🤔

[ssbarnea]

Yeah, i was wondering about this. The funny bit is that it does not always happens. I got it in some places but not on others and I was not able to identify the source yet. I also use mise a lot and this might also have a role in it.

It looks very similar with pre-commit/pre-commit#2409

Yes, it is an upstream bug coming from pre-commit own health_check, here are the details:

• python returns version string as 3.14.0.candidate.2 makes their _version_info return virtualenv_version = '3.14.0'.
• the uv created venv produces version_info = 3.14.0rc2
• i also have a python 3.14 installed by mise instead of uv and that one returns version as:

# uv python3.14
> uv run --python=3.14 python --version
`Python 3.14.0rc3+`
> uv run --python=3.14 python -S -c 'import sys;print(".".join(str(p) for p in sys.version_info))'
3.14.0.candidate.3
# puts `3.14.0rc3` into pyenv.cfg

# mise python3.14
> python --version
Python 3.14.0rc2
> python -S -c 'import sys;print(".".join(str(p) for p in sys.version_info))'
3.14.0.candidate.2
# puts 3.14.0rc2 inside pyenv.cfg

> python3.13 --version
Python 3.13.7
❯ python3.13 -S -c 'import sys;print(".".join(str(p) for p in sys.version_info))'
3.13.7.final.0
# puts 3.13.7 inside pyvenv.cfg

This makes me believe that pre-commit does not support pre-releases of python interpreters in general, not related to uv in particular. As its own healthcheck function will fail because it fails to translated the rc2. With final it works as it just drops it.

This would be fixed by replace current implementation with sys.version.split()[0] which is the version that is saved inside pyenv.cfg file, but it gets more nuanced:

• uv venv records version_info = 3.14.0rc3
• python -m venv records version_info = 3.14.0
• python -m virtualenv records version_info = 3.14.0.candidate.2

As you can see each of them records a different version format inside pyenv.cfg. pre-commit healthcheck happens to work with last two just because it drops.

The tricky bit is that due to my very low success rate on proposing pull-requests to pre-commit project, I will not be able to propose a patch for improving its behavior as it will be refused for sure. Also just mentioning uv would likely have it closed anyway.