Switch to official setup-python's 3.13t

[ddelange]

unofficial one had a bug (?) ref #52 (comment)
official one was released ref actions/setup-python#973 (comment)

[ddelange]

Hi @davidhewitt 👋

despite free-threaded python now being GA on actions/setup-python side, the above-mentioned bug still persists for windows. can you please double check that this is not maturin-action?

if it is not, would you be so kind to open a bug report with your context of maturin's path discovery?

[ngoldbaum]

despite free-threaded python now being GA on actions/setup-python side, the above-mentioned bug still persists for windows. can you please double check that this is not maturin-action?

What you're running into is just how the python.org installer is documented to work on Windows for the free-threaded build. See https://docs.python.org/3.13/using/windows.html#installing-free-threaded-binaries and in particular note:

Python source files and bundled third-party dependencies are shared with the main install.

So I think this is just a huge footgun that setup-python inherits from upstream :(

The only real fix is to separate out the install into its own actions run. Or use a nuget python. See https://py-free-threading.github.io/installing_cpython/#pythonorg-and-nuget-installers.

[ngoldbaum]

We should also try to make setup-uv and the python-build-standalone python builds from uv play more nicely with pyo3. There are rpath issues that block just completely replacing setup-python with setup-uv everywhere it might make sense.

[ddelange]

Thanks for the context @ngoldbaum!

Will close this PR with that, because with #64 merged it's fine as it is right now.

[oconnor663]

Thanks a million both of you for figuring this stuff out. I dread debugging stuff like this 😅