Support for native extension doctests

[kevinheavey]

I originally raised this issue in the Pytest repo pytest-dev/pytest#9711 but the response was that it was probably not in scope, but that maybe pytest-doctestplus would be interested:

Currently pytest --doctest-modules does not pick up native extension modules (those written in C, Rust etc). This was raised several years ago but closed because the author made a plugin for Cython only pytest-dev/pytest#1498.

I don't know what docstring conventions people use for C or C++, but I do know people are writing Python libraries using Rust (example) and the objects from these modules can have __doc__ attributes.

Currently I can test the docstrings in such modules by setting up Sphinx docs and using Sphinx's make doctest command, but I would prefer not to use Sphinx at all.

So would support for native module doctests be in scope for pytest-doctestplus? Speaking naively, I think it would be a matter of importing the module, checking the __doc__ attribute of every member and running any doctest-style examples that are found.

[pllim]

pytest-doctestplus is primarily to support packages within the Astropy Project ecosystem. There was a brief discussion of maybe even moving this upstream to pytest (#100) but nothing came of it.

Given that the Project currently has no need for this feature, it is likely out of scope, but I will keep this issue open in case others want to chime in.

Thanks for your interest in this package!