Autodoc includes inherited and undocumented attributes if extensions make use of ``AttributeDocumenter.import_object``

Describe the bug

When an extension makes use of AttributeDocumenter.import_object and a parent exists, this then calls .update_annotations and overwrites the __annotations__ of the parent.
This happens (or can happen?) before the import mechanics (e.g. importer.py:get_class_members) get the various members of a class, and as a result too many attributes may be included.

The original bug report for this is https://github.com/Chilipp/autodocsumm/issues/95. A nice example is given there.
Autodocsumm needs to call .import_objects to do some additional checks on the object.

I have tried to trace this further than the original bug report. Being not very familiar with the Sphinx codebase, this is not trivial, so my explanation above may not be entirely correct.

In my opinion, the solution would probably be to not modify the original __annotations__ but rather store the discovered annotations separately.

On the other hand, if this turns out to not be a bug, a workaround needs to be found in autodocsumm.

I'd like some guidance here and maybe I can submit a PR or fix this in autodocsumm alternatively.

How to Reproduce

pip install sphinx autodocsumm
sphinx-quickstart --no-sep --project test --author me -l en -r 0.0.1

In config.py, add

extensions = [
    'autodocsumm',
    'sphinx.ext.autodoc',
]

Add python module samplecode/__init__.py to root directory, with content of __init__.py being

class Foo:
    """
    Foo is a class that does not inherit from anything
    """

    classattr: str = "MyClassAttr"
    """
    This is a class attribute
    """

    def __init__(self):
        self.instance_attr: str = "MyInstanceAttr"
        """
        This is an instance attribute
        """

        self.typed_instance_attr: str = "MyTypedAttrNoDocs"


class Bar(Foo):
    """
    Bar is a class that inherits from Foo
    """

    def __init__(self):
        self.other_instance_attr: str = "MyOtherInstanceAttr"
        """
        This is annother instance attribute
        """

        super().__init__()

Content of index.rst

test-docs documentation
=======================


.. automodule:: samplecode
   :members:
   :autosummary:

to build the docs, run

python -m sphinx -M html . _build

You will then notice that the output in index.html includes "instance_attr" for both classes, even though this is an inherited member for Bar and should not be included.

Environment Information

Platform:              win32; (Windows-10-10.0.19044-SP0)
Python version:        3.12.1 (tags/v3.12.1:2305ca5, Dec  7 2023, 22:03:25) [MSC v.1937 64 bit (AMD64)])
Python implementation: CPython
Sphinx version:        7.4.7
Docutils version:      0.21.2
Jinja2 version:        3.1.4
Pygments version:      2.18.0

Sphinx extensions

[
    'autodocsumm',
    'sphinx.ext.autodoc',
]

Additional context

The original issue also mentions that undocumented attributes are included. I'm failing to reproduce that part currently. But I had managed to reproduce it previously.

Reproduce the example with autodocsumm and inspect AttributeDocumenter.import_object alongside importer.py:get_class_members, focusing on when parent annotations is updated. Done means the build no longer includes inherited or undocumented attributes incorrectly, while the documented attribute behavior remains correct.