Re-enable mypy and sync mypy.ini from skeleton

[Avasam]

Summary of changes

Ref https://github.com/jaraco/skeleton/issues/143

Pull Request Checklist

• [ ] Changes have tests
• [ ] News fragment added in newsfragments/. (See documentation for details)

[Avasam]

The "Fix ConfigHandler generic" commit is related to https://github.com/python/mypy/issues/17631#issuecomment-2277491389 (same symptoms). Not sure why it wasn't failing before, didn't fail locally (granted I'm running from Windows on 3.9, so it could be environment-specific, despite version/platform flags), and only failed on the CI on (MacOS and/or 3.12)[^1].

But it still revealed an underlying misuse of the TypeVar

[^1]: No other MacOS or Python 3.12 action had time to complete, so idk which one was the specific cause.

[jaraco]

I still see some test failures.

_________________________ setuptools/config/expand.py __________________________
[gw3] linux -- Python 3.10.14 /home/runner/work/setuptools/setuptools/.tox/py/bin/python
206: error: "type: ignore" comment without error code (consider "type: ignore[union-attr]" instead)  [ignore-without-code]
291: error: "type: ignore" comment without error code (consider "type: ignore[assignment]" instead)  [ignore-without-code]
362: error: "type: ignore" comment without error code (consider "type: ignore[call-overload]" instead)  [ignore-without-code]
______________________ setuptools/config/pyprojecttoml.py ______________________
[gw3] linux -- Python 3.10.14 /home/runner/work/setuptools/setuptools/.tox/py/bin/python
48: error: "type: ignore" comment without error code (consider "type: ignore[union-attr]" instead)  [ignore-without-code]
__________________________ pkg_resources/__init__.py ___________________________
[gw0] linux -- Python 3.10.14 /home/runner/work/setuptools/setuptools/.tox/py/bin/python
2780: error: "type: ignore" comment without error code (consider "type: ignore[arg-type]" instead)  [ignore-without-code]
__________________ setuptools/tests/test_editable_install.py ___________________
[gw2] linux -- Python 3.10.14 /home/runner/work/setuptools/setuptools/.tox/py/bin/python
881: error: "type: ignore" comment without error code (consider "type: ignore[index]" instead)  [ignore-without-code]
883: error: "type: ignore" comment without error code (consider "type: ignore[index]" instead)  [ignore-without-code]
891: error: "type: ignore" comment without error code (consider "type: ignore[index]" instead)  [ignore-without-code]
892: error: "type: ignore" comment without error code (consider "type: ignore[index]" instead)  [ignore-without-code]

What's the plan for those?

Also, thanks for reconciling the differences between setuptools' and skeleton's mypy.ini.

[Avasam]

I still see some test failures. What's the plan for those?

I rebase and fix them 😃

[Avasam]

@jaraco Bump on this since currently static typing validation from mypy is disabled (at least pyright's running). And some of my pending PRs should be validated by it.

[Avasam]

Other PRs started failing too with a strange error (not the same though), so CI failure may or may not be related to these changes (although I don't see which of my changes could cause it)

[Avasam]

Now that the weird CI issue seems resolved. I'd like to merge this before bumping mypy to 1.12. And to unblock #4504