Add --pep561-override option to declare package names that are always considered typed

[ntninja]

Title says it all: Packages declared using this option will not be ignored as found module but no type hints or library stubs.

This is intended as a last resort if one depends on a library that neither provides type hints and there are no external typing stubs available. In my specific use-case I depend on a library that provides some type hints in the code base, but they are incomplete/spotty and so the library authors prefer to not mark the package as PEP-561 compatible until they are more usable. They are still quite helpful when used from mypy however when one keeps their limitations in mind.

This still lacks docs and tests, but I'd like to hear what people here think about this before going down that road.

[ethanhs]

I depend on a library that provides some type hints in the code base, but they are incomplete/spotty and so the library authors prefer to not mark the package as PEP-561 compatible until they are more usable.

Ideally in this situation, a stub package should be created I would argue. This allows for iteration on types (and opting into them while they are unstable) while keeping the main package stable.

I will think about this more.

[ethanhs]

the library authors prefer to not mark the package as PEP-561 compatible until they are more usable.

I have opened #8545 to discuss this further.

[97littleleaf11]

Hello! Any progress on this PR?

[ethanhs]

I think this will be superseded by an implementation of #8545