Using uv to simplify and speedup the CI

[Avasam]

uv is a fast and modern (mostly) drop-in replacement for setup-python, pip, build, venv, twine¹, made by the same folks as Ruff.
I've been using uv for over a year and it's a game-changer for packaging and environment management. pywin32 is pretty simple, being Windows-only and having no runtime dependencies, but we can still benefit from a pretty significant speedup.

In the times below, I omitted the slowest and fastest times in a job matrix as outliers. The exact time save is hard to say, but the trend is clear:

• The CI step of installing Python (all jobs except native builds) goes from (sometimes²) 50-60s down to 6-14.
• The CI step of installing build for cross-compilations goes from 3-14s down to 0 (no need to install extra dep)
• The CI step of installing checkers dependencies from ~9s down to ~2s
• The CI step of installing type-checkers dependencies from 37-44s down to ~3s

Footnotes

1. Whilst uv publish can be used to replace twine for publishing, there are no changes needed to your current workflow and you can keep using twine as you were. ↩

2. Most of the time, the actions/setup-python step takes 6-18s, which would be equivalent, but it also sometimes randomly take around a minute for unknown reasons. ↩

[Avasam]

There already was nothing to cache here.

I also kept setup-python to keep testing in a global user install (this can still be done with uv if you pre-install Python, but at this point having actions/setup-python + astral-sh/setup-uv wouldn't bring any benefit for this step if there's no dependency to quickly install.

[mhammond]

uv looks great - I guess I don't really see a downside here and a few upsides - thanks!

[Avasam]

Glad you think so!
And yeah I wouldn't wanna force a contributor to use uv if I can avoid it. (Especially since being a drop-in replacement for pip is a selling point)