Missing documentation of python class with decorators.

[kangcliff]

Describe the bug

When generating documentation for class with decorators, Sphinx recognizes the wrapped class as the wrapper function returned by the top decorator instead of the actual class being wrapped by decorators.

How to Reproduce

index.rst

.. automodule:: test_sphinx
    :members:
    :show-inheritance:
    :undoc-members:

test_sphinx.py

def Singleton(class_):
    """A singleton decorator"""
    instances = {}

    def getinstance(*args, **kwargs):
        if class_ not in instances:
            instances[class_] = class_(*args, **kwargs)
        return instances[class_]

    return getinstance

@Singleton
class Foo:
   """An example class."""

   def bar(self):
      """An example function."""
      pass

Environment Information

Platform:              Ubuntu 22.04;
Python version:        3.10.13 (GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-44).GCC: (GNU) 7.3.1 20180303 (Red Hat 7.3.1-5).)
Python implementation: CPython
Sphinx version:        5.3.0

Sphinx extensions

No response

Additional context

No response

[picnixz]

I confirmed the behaviour. At runtime, Singleton is a function and not a class anymore and it appears we do not statically analyze the decorated class before choosing the correct documenter. I think the reason why it's like this is because the documenter being involved is the one for documenting functions (since the runtime type is a function) and not a class anymore; however, IIRC, the documenter is determined before the module is statically analyzed...