Decorator factory all documented as "alias of"

Describe the bug
I have a library module where functions have decorator versions generated for them via a factory function. The newly generated decorators have docstrings inherited from the base function. Factory code below, for context, see https://github.com/ZaxR/bulwark/blob/master/bulwark/decorators.py:

def decorator_factory(decorator_name, func):
    """Takes in a function and outputs a class that can be used as a decorator."""
    class decorator_name(BaseDecorator):
        __doc__ = func.__doc__
        check_func = staticmethod(func)

    return decorator_name

When I check the docstrings via the code, everything looks fine, but my Sphinx docs show each decorator's docstring as:

alias of bulwark.decorators.decorator_factory.<locals>.decorator_name

See https://bulwark.readthedocs.io/en/latest/_source/bulwark.decorators.html#bulwark.decorators.HasColumns .

To Reproduce
Steps to reproduce the behavior:

<Paste your command-line here which cause the problem>

$ git clone https://github.com/ZaxR/bulwark.git
$ cd bulwark
$ pip install -e ".[dev]"
$ cd docs
$ make html
$ # open _build/html/bulwark.decorators.html and see the descriptions

Expected behavior
I would like the factory-generated decorators to each show their docstring in the Sphinx docs.

Your project
https://github.com/ZaxR/bulwark

Screenshots
Example on readthedocs: https://bulwark.readthedocs.io/en/latest/_source/bulwark.decorators.html#bulwark.decorators.

Environment info

• OS: [e.g. Unix/Linux/Mac/Win/other with version]
• Python version: 3.8.2
• Sphinx version: 2.4.4
• Sphinx extensions: [
  'm2r',
  'sphinx.ext.autodoc',
  'sphinx.ext.autosummary',
  'sphinx.ext.doctest',
  'sphinx.ext.intersphinx',
  'sphinx.ext.todo',
  'sphinx.ext.coverage',
  'sphinx.ext.viewcode',
  'sphinx.ext.napoleon',
  'sphinxcontrib.apidoc',
  ]
• Extra tools: [Browser]

Additional context
Link above is to the readthedocs, but the same behavior is observed locally as well.

• Re: https://github.com/ZaxR/bulwark/issues/3

Reproduce the issue by cloning bulwark, installing its development dependencies, and running make html from docs. Inspect the generated bulwark.decorators page and Sphinx's autodoc behavior; done when factory-generated decorators display their inherited docstrings instead of an "alias of" description.