Test failure with Python 3.9

[ghost]

Hypothesis test test_typeddict_with_optional_then_required_again in hypothesis-hypothesis-python-5.5.1/hypothesis-python/tests/cover/test_lookup_py38.py fails with Python 3.9.

I have tried to debug this issue, but I am quite lost in the project's logic.

I have at least prepared an environment in which it is possible to reproduce:
https://github.com/Dormouse759/fedora-rawhide-cont

Once built, just run ./reproduce.sh inside the container.

Downstream issue: https://src.fedoraproject.org/rpms/python-hypothesis/pull-request/6#comment-36386

Should you have any directions where to look, I will gladly give this bug a second try.

[Zac-HD]

Related pull requests: #2208 (Hypothesis 4.45), python/cpython#17214 (for 3.9), python/typing#687 (unreleased)

Blast. I'll just redact the rest of the investigation and the swearing - turns out that while the logic in Hypothesis is correct, I think I got the logic for propagation of non-optional keys where others are optional wrong in CPython. I'll need to fix it (and add more tests) upstream there and in typing_extensions 😬

My sincere thanks for reporting this before it made it into a release!

[hroncok]

@Zac-HD Could you pleas point to the fixer?

[Zac-HD]

Not fixed yet, I'd just closed it because I think it's an upstream issue. Reopening until I have a concrete reference (or fix) to point to instead.

[hroncok]

Thanks.

[hroncok]

Seem to be OK with hypothesis 5.8.0 and Python 3.9.0a5.

[Zac-HD]

Seems to be working, so... 🤷‍♂️