Add mixins module to asyncio

[sobolevn]

No description provided.

[sobolevn]

I am checking what CI will say about adding module to VERSIONS, but not to the module. Source: https://github.com/python/cpython/commits/main/Lib/asyncio/mixins.py

[sobolevn]

This module does not have any public objects, but we can still add several protected ones. I don't know how they are supposed to be used though.

[sobolevn]

stubtest is still failing for <3.9 🤔
https://github.com/python/typeshed/runs/4686388253?check_suite_focus=true

[srittau]

@sobolevn In theory, mypy should support this: python/mypy#11069, but in practice, asyncio.exceptions is also ignored in the stubtest allowlists. You need to do the same with asyncio.mixins for now.

[srittau]

python/mypy#12062

[sobolevn]

@srittau @Akuli can you please help me? I don't understand why tests fail:

Run python tests/stubtest_stdlib.py
error: asyncio.mixins failed to find stubs
Stub:
MISSING
Runtime:
None

It happens on all python versions <3.10, when this module was introduced. But, I've marked it appropriately in VERSION file 🤔

[AlexWaygood]

Could you update the classes in asyncio.locks and asyncio.queues so that they inherit from _LoopBoundMixin, as they do at runtime?

[srittau]

Maybe we should just skip the loop argument, It can't really be used. Then we can also remove _marker above.

[srittau]

See my comment above, but I'm fine either way.

[sobolevn]

@AlexWaygood sure, in an hour 👍

[sobolevn]

I went for loop: NoReturn. I think that it can be the best solution:

1. It should not require any stubtest hacks
2. It indicates that loop is not allowed

And also, looks like the change proposed by @AlexWaygood will require some extra tweaks, so I am going to leave this for some next PRs (while thinking about the best way to implement it).

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉