Missing type exports for vendored `py`

[The-Compiler]

I want to report a side effect of this change when using mypy. py used to be typed, while apparently the vendored library is not. Downstream developers that define pytest hooks may now see mypy errors like:

nbvalx/pytest_hooks_notebooks.py:32: error: Skipping analyzing "py": module is
installed, but missing library stubs or py.typed marker  [import]
    import py
    ^
nbvalx/pytest_hooks_notebooks.py:32: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
nbvalx/pytest_hooks_notebooks.py:412: error: Argument 2 to "collect_file"
becomes "Any" due to an unfollowed import  [no-any-unimported]
    def collect_file(file_path: pathlib.Path, path: py.path.local, parent:...
    ^

I'll leave it to you to decide if it is worth it to add back that support (downstream developers can easily add a couple of ignores, especially knowing that py.path is being deprecated anyway), but I want to report this here for future reference because at the beginning I couldn't wrap my head around what had happened (latest py release was one year ago, and surely I had ran my CI last week without errors) and it took me a while to figure out what was going on.

Cheers,
Francesco

Originally posted by @francesco-ballarin in #10396 (comment)

[The-Compiler]

I'm not too familiar with how exporting type information works - could we perhaps just vendor pylib's path.pyi with pytest? Or would that conflict with the fact that we don't actually want to install a py package with pytest?

[francesco-ballarin]

In a normal package that would work, I believe. I am not sure however if the hack in #10396 would fall under the "normal package" category.

[asottile]

we could maybe provide a py-stubs package -- though I'd have to check if py/py.typed still overrides that (which would be necessary / desirable)?