PEP 561: Clarify the rules for extension only packages

[AWhetter]

PEP-0561 does not mention extension packages, packages that consist of just an .so file. Given that PEP-484 mentions extension modules as a use case for stub files, should PEP-561 make it more clear what the ideal layout of an extension only package is?
It appears to be valid to have a package structure like the following:

.../site-packages/
    mypackage/
        __init__.pyi
        py.typed
    mypackage.cpython-37m-x86_64-linux-gnu.so

[AA-Turner]

We rarely update Accepted PEPs -- this might be better to add to typing documentation. Pinging @ethanhs as author and @JelleZijlstra as a typing ecosytem expert for where the best place to put this information would be (CPython typing docs, python/typing docs, etc).

A

[emmatyping]

PEP 561 does say

This PEP does not support distributing typing information as part of module-only distributions .;.. The single-file module should be refactored into a package and indicate that the package supports typing as described above.

So I think your layout is correct. I think this could be clarified in the python/typing docs.

[JelleZijlstra]

Yes, an issue on the PEPs repo isn't the right place to discuss this. I think we can put it in https://typing.readthedocs.io/en/latest/ (still under construction), so feel free to open an issue over at github.com/python/typing.

[AWhetter]

I've opened an issue with typing, which is linked above. Thank you for the help everyone!