Type hints are irregularly documented (+link generation broken)

Describe the bug

Sphinx processes and outputs type hints differently to html depending on

• the use of quotes on type hints ("Type" vs Type),
• if __future__.annotations is present, and
• on the type of import
  • plain import: import module
  • from import: from module import name
  • type checking import:

    from typing import TYPE_CHECKING
    if TYPE_CHECKING:
        from module import name
    

In some cases the full canonical path including all levels of module path is
shown (like: module.Name), some others show only the class name
(like: Name). Some of the combinations also break links.

Here is what I found:

                                | __future__.annotations  | no __future__.annotations |
                                |  unquoted   |  quoted   |  unquoted    |   quoted   |
--------------+-----------------+-------------+-----------+--------------+------------|
plain import  | module function |    F, L     |   F, L    |     F, L     |    F, L    |
              | class attribute |    F, L     |   F, L    |     F, L     |    F, L    |
              | class property  |    F, L     |   F, L    |     F, L     |    F, L    |
              | class method    |    F, L     |   F, L    |     F, L     |    F, L    |
from import   | module function |    F, L     |   C, L    |     F, L     |    F, L    |
              | class attribute |    F, L     |   C, N    |     F, L     |    F, L    |
              | class property  |    F, L     |   C, N    |     F, L     |    F, L    |
              | class method    |    F, L     |   C, L    |     F, L     |    F, L    |
type checking | module function |    C, L     |   C, L    |     n/a      |    C, L    |
              | class attribute |    C, N     |   C, N    |     n/a      |    C, N    |
              | class property  |    C, N     |   C, N    |     n/a      |    C, N    |
              | class method    |    C, L     |   C, L    |     n/a      |    C, L    |

F == full path,
C == class-only,
L == link works,
N == no link,
n/a == does not apply (__future__.annotations is required)

Observations:

• Plain imports always generate canonical paths and working links.
• with future annotations, quoted types that were imported with the from-import
  schema behave differently that unquoted types and some links are broken
• the same behavior occurs if type checking imports are used no matter if quoted
  or not

Note: Showing classes-only is really neat (especially for small projects) as it is more concise. But it would be best if this could be configured (enabled/disabled).

How to Reproduce

$ git clone https://github.com/gschwaer/sphinx_test/
$ cd some_project
$ git checkout autodoc_irregular_type_resolving
$ python3 -m venv .venv
$ pip install -r requirements.txt
$ make
$ # open _build/html/index.html

Check out Test.py which has the include of __future__.annotations at the top.

Expected behavior

• The generated documentation should not depend on the way a type is imported.
• Types should be linked correctly.
• Showing types without the module prefix makes a lot of sense in some situations and in others, it doesn't. This should be configurable.

Your project

https://github.com/gschwaer/sphinx_test/tree/autodoc_irregular_type_resolving

Screenshots

Example showing the case where types are shown as full canonical path and links work (with future annotations, from-import schema, type hints not quoted):

Example showing the case where types are shown as class-only and some links are not generated (the generated links work) (with future annotations, from-import schema, quoted type hints):

OS

Linux

Python version

3.8.10

Sphinx version

4.2.0

Sphinx extensions

sphinx.ext.autodoc

Extra tools

No response

Additional context

I am using RTD theme because alabaster is really not helping to showcase this issue. The effects (class-only vs full path and missing links) are the same for both themes.

Reproduce the issue using the linked sphinx_test repository and its autodoc_irregular_type_resolving branch; install requirements and run make. Start with Test.py and inspect the generated _build/html/index.html across the import and annotation combinations described. Done means type rendering is consistent, links work, and the module-prefix behavior is configurable.