Run CI for Python 3.14.0 and free-threading

[cdce8p]

No description provided.

[cdce8p]

This could be updated if PEP 780 get's accepted. It's still a draft though at the moment.
https://peps.python.org/pep-0780/#examples

[ngoldbaum]

Hopefully lxml will have a free-threaded release out soon. My next task today is to run the lxml tests under TSan to hopefully validate a final set of fixes.

[cdce8p]

Looks like there is just one flaky test for the free-threading build.

mypy/test/teststubgen.py::StubgenPythonSuite::stubgen.test::testImportedModuleHardExits_import

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[ngoldbaum]

Hi! I missed this and opened #20076. I think the failing test in the CI will be fixed when Python 3.14.1 comes out. The issue is fixed in the 3.15, 3.13, and as of yesterday also the 3.14 development branch.

The 3.14 release schedule says we might have to wait until December for 3.14.1, so it might make sense to simply skip the failing tests for now.

[emmatyping]

The 3.14 release schedule says we might have to wait until December for 3.14.1, so it might make sense to simply skip the failing tests for now.

I think this makes sense. I'd normally suggest we do a sys.version_info == (3, 14, 0)), but I don't think that can be encoded in our test harness at the moment.

[cdce8p]

The 3.14 release schedule says we might have to wait until December for 3.14.1, so it might make sense to simply skip the failing tests for now.

Normally I'd agree. However it might be a bit more difficult. AFAICT it's not just one test but up to 5-10 different ones (?) which are failing each time. Not sure I'm comfortable with skipping this many.

Yes, December is still two months away, however users are still able to use the pure Python version so there is at least an option for them. Technically they could also compile mypy from the sdist themselves. It might be better to just wait and add the free-threading version then.