Implement flag to allow typechecking of untyped modules

[DeinAlptraum]

Add a flag and config ini options "enable_installed_packages". Setting it to True instructs mypy to typecheck also modules that do not have stubs or a py.typed marker.

Fixes #8545

[DeinAlptraum]

@hauntsaninja can you tell me by any chance if there's anything I'm missing/I should do to get a review here?

[DeinAlptraum]

Ping. Can someone review this? @JelleZijlstra can you help me with this?

[DeinAlptraum]

Ping. @hauntsaninja @JelleZijlstra can you tell me what I need to do to get a review here?

[DeinAlptraum]

Ping @hauntsaninja @JelleZijlstra @JukkaL

[JelleZijlstra]

Mypy development is unfortunately under-resourced and personally I don't have much time available to review PRs. I'd advise you to wait and hopefully a committer will come along and review this.

[Xiddoc]

I feel like this feature is crucial and affects way too many people for it to be ignored. Using type: ignore or manually adding a py.typed file to every used third-party module is incredibly impractical.

Could this at least get a CR, if improvements are needed then the community can follow up on issues for the PR. ❤️
@JukkaL @hauntsaninja

[JukkaL]

I can try to review this -- possibly next week. It would help if the merge conflict was fixed.

[DeinAlptraum]

Thanks for the comment, didn't notice the merge conflict. I wish there were notifications for this... anyway, fixed.

[hauntsaninja]

Thanks! I think the per-module handling isn't quite right, in particular, I'm not sure it handles globs correctly. I'd also vote for a slightly more specific name, maybe something like --follow-untyped-imports. This matches the untyped-import error code the current implementation will silence.

[DeinAlptraum]

@hauntsaninja thanks for the feedback! You're right, this wasn't handling globs properly. In the process of fixing that, I also noticed that my solution was more complicated than necessary and simplified it a bit...

Regarding the name: it seems there was quite a lot of discussion about how the config option should be called on the original issue, so I wasn't sure what to pick. Yours definitely sounds better though, so changed it to that for now.

[github-actions]

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