I work on a project called python-openzwave. I have rewritten the build system for this library. The library makes use of a CPP library called OpenZWave. This library gets compiled by the build system. Cython is what is used for the "bridge" between python code and the cpp code in OpenZWave. The output of this process is a single pyd file. I would like to be able to create a stub file for this pyd file. I have encountered an issue when creating documentation for the library where if the library is already installed on the system and the build system imports the newly created pyd file python crashes. So a direct import of the new file cannot be done. Using the code example below I am able to import the new library and avoid the application crash.

import os
import imp

mod_file = os.path.join(build_dir, 'libopenzwave.pyd')
mod = imp.load_dynamic(
    'libopenzwave',
    mod_file
)
    
sys.modules['libopenzwave'] = mod

I am unsure of how stubgen handles the importation of c extensions. I am needing to build the stub file at build time so I have subclassed setuptools.Command to acomplish this task,

the code below is what is used in the run method of the class

        from mypy import stubgen
        import sys

        builder = self.distribution.get_command_obj('build')
        build_path = builder.build_lib
        build_ext = self.distribution.get_command_obj('build_ext')
        extension = self.distribution.ext_modules[0]
        ext_path = build_ext.get_ext_fullpath(extension.name)

        if sys.version_info[0] < 3:
            args = ['--py2']
        else:
            args = []

        args += [
            '--include-private',
            '--output',
            build_path,
            ext_path
        ]

        options = stubgen.parse_options(args)
        stubgen.generate_stubs(options)

when this runs the program exits with the following error

Critical error during semantic analysis: mypy: can't decode file 'build\lib.win-amd64-3.7\libopenzwave.pyd': 'utf-8' codec can't decode byte 0x90 in position 2: invalid start byte

using the positional file is the only way to be able to direct the program to load the proper pyd file. Is there a special way to go about passing the path and filename of the c extension that I want to create the stub file for? or do I have to use the imp module as outlines in the code block above and set the module into sys.modules and then pass the module name to stubgen?