autodoc doesn't handle TypeVars or document user-defined generic classes accurately

[anselor]

Describe the bug

1. TypeVar aliases aren't resolved
   When using automodule, if a TypeVar is used, the TypeVar isn't being recognized. With nitpick on, this warning is generated:
   helloworld.py:docstring of helloworld.helloworld.MyGenericType.foo:: WARNING: py:class reference target not found: MyTypeVar
   I can add it to the nitpick ignore list, but then all of the parameters that reference it aren't recognized and linked.

2. typing.Generic type parameters for user-defined generic classes aren't documented

3. Constructor for user-defined generic classes are always (*args, **kwargs) instead of what's actually declared.

To Reproduce

Simple doc file index.rst:

Hello World
===========

code docs
=========

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

Here's an example module helloworld.py:

from typing import Generic, TypeVar

MyTypeVar = TypeVar('MyTypeVar')

class MyGenericType(Generic[MyTypeVar]):
    def __init__(self, param: MyTypeVar) -> None:
        pass

    def foo(self, param: MyTypeVar) -> None:
        pass

Expected behavior
Ideally:

1. I would expect TypeVar definitions to be recognized as types
2. Generic classes should document the TypeVars passed to typing.Generic
3. Constructor for generic classes should reflect the parameters declared in the constructor.

Work-around for Item 1

This is less than ideal, but I can get the TypeVar to resolve by manually documenting it as an attribute like this:

.. py:attribute:: MyTypeVar
   :type: TypeVar
   :value: TypeVar('MyTypeVar')

This is the type used in MyGenericClass

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

Your project
I've included a simple example above

Screenshots
Here's the generated documentation:

Here's the generated output with the manual attribute work-around:

Environment info

• OS: Ubuntu 18.04, Ubuntu 20.04
• Python version: 3.6.9, 3.8.2
• Sphinx version: 3.1.2, 3.2.1
• Sphinx extensions: sphinx.ext.autodoc
• Extra tools: Viewing output on Chrome

Additional context

[electric-coder]

Functional solution was demonstrated at Stack Overflow.

EDIT:

It worked for me due to old caches. After invalidating caches I confirm the problem in the question of the typing.Generic not being correctly displayed in the class inheritance signature does occur.

Environment

Windows 10
Python 3.8.0 + Sphinx 3.2.1
Python 3.7.7 + Sphinx 3.1.1

[anselor]

I also added the additional options described in the Stack Overflow link and also continue to have this issue. I'm using the alabaster theme, but I don't think that matters.

I also added this to conf.py to force __init__() to be documented and the parameters are correctly resolved on __init__()

def skip(app, what, name, obj, would_skip, options):
    if name == '__init__':
        return False
    return would_skip


def setup(app):
    app.connect('autodoc-skip-member', skip)

[tk0miya]

1. I would expect TypeVar definitions to be recognized as types

Please add a comment (starting with a colon) to the typevar. Then autodoc detects it automatically.

#: blah blah blah
MyTypeVar = TypeVar('MyTypeVar')

3. Constructor for generic classes should reflect the parameters declared in the constructor.

Now I posted #8229 to fix this.

2. Generic classes should document the TypeVars passed to typing.Generic

I need time to fix this.

Note: The arguments of Generic are lost in __mro__. So we need to refer __orig_bases__ instead.
see https://www.python.org/dev/peps/pep-0560/ in detail.

[anselor]

I've not seen the #: comment syntax before. That appears to have addressed that issue. Thank you.

[tk0miya]

It has been described at autoattribute's document.
https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html#directive-autoattribute

[anselor]

I'm still having issues with the first item.

It looks like if my module is in a package, the reference to the typevar doesn't preserve the package name of the typevar alias and is unable to locate it.

If I manually create a attribute in the global scope that matches the name of the typevar alias, then autodoc is able to locate that manually defined attribute.

[tk0miya]

@anselor Could you file another issue with detailed information? It would be very helpful if there is an example code!