(🎁) Adopt pre-commit.ci

[KotlinIsland]

The last remaining incomplete task from adopting black (#12424/#10996) is to add the pre-commit GitHub app to the mypy project.
I believe only owners have permission to do so. (@JukkaL)

[AlexWaygood]

@JukkaL, thoughts on this? It works really well over at typeshed; I think it would be a big quality-of-life improvement for contributors :)

[ssbarnea]

It is like crack! A huge help and productivity boost for incoming PRs as it does report problems in seconds and can also fix basic mistakes, reducing the polishing time considerably. I used it for 3-4 years by now.

PS. I see that current pre-commit config uses only 3 hooks, I know few more that could help so there is space for improvement there too.

[JukkaL]

Yeah, this sounds like a good idea. I'm not sure if I can do this, however, since mypy is under the Python org.

[AlexWaygood]

I'm not sure if I can do this, however, since mypy is under the Python org.

So is typeshed, but @JelleZijlstra managed to enable it for that repo without issues!

[JelleZijlstra]

That prompted me to try whether I could do it for mypy too. I went through the flow on pre-commit.ci and tried to add mypy, but I think I only "requested" it. Maybe Jukka has enough access to actually enable it.

[ikonst]

@ssbarnea mypy's self-check might be a good candidate :) though probably as a 'system' hook rather than using pre-commit's mypy hook, since the latter wouldn't have our custom plugin.

Update: #15084

[hauntsaninja]

Thanks to @ambv , we got pre-commit.ci added to the repo. #15116 shows that it works

[ssbarnea]

The next move would be to replace flake8 with ruff, something I started about a month ago on ~10 project, it is awesome.