Use type hints extracted from docstring for native extension

[jfolz]

For native code extension modules sphinx autodoc extracts the function signature, including type hints, from the first line of the docstring when autodoc_docstring_signature is set.
I dug around pretty deep in the code and as far as I can tell all of the methods used by this extension tap into the __annotations__ dict, which native functions don't have. Can this extension be configured to use the signature extraction that sphinx provides?
I guess I should add that I'm using napoleon with Google style docstrings, following #15, but writing :param:s directly doesn't make any difference.

Below is my current solution (to be put in conf.py). It works, but it's exceedingly janky and will probably breaks in many exciting ways in the future.

TYPE_HINTS = {}


# Record type hints
def record_type_hints(app, what, name, obj, options, signature, return_annotation):
    TYPE_HINTS[name] = {}
    if signature is not None:
        for arg in signature.strip('()').split(','):
            k, _, v = arg.partition(':')
            k = k.strip()
            v = v.strip()
            if k and v:
                TYPE_HINTS[name][k] = v
    if return_annotation is not None:
        TYPE_HINTS[name]['return'] = return_annotation
    return signature, return_annotation


# Add recorded type hints to function parameters
def add_type_hints(app, what, name, obj, options, lines,
                   __param_pattern=re.compile(r'^:param ([^:]+):')):
    rtype = False
    for i, line in enumerate(lines):
        m = __param_pattern.search(line)
        if m is not None:
            arg = m.groups(0)[0]
            hint = TYPE_HINTS[name].get(arg)
            if hint:
                lines[i] = line.replace(f':param {arg}:', f':param {hint} {arg}:', 1)
        elif line.startswith(':rtype:'):
            rtype = True
    if not rtype and TYPE_HINTS[name].get('return'):
        lines.append(f':rtype: {TYPE_HINTS[name].get("return")}')


def setup(app):
    app.connect("autodoc-process-signature", record_type_hints)
    app.connect("autodoc-process-docstring", add_type_hints)

[jfolz]

Is already broken for default values ;)

[gaborbernat]

I'd say the path ahead for this would be to support stub files, for which there's another issue.