Issues with overriding/re-implementing BaseModelAdmin.formfield_for_manytomany

[blueyed]

I am overriding BaseModelAdmin.formfield_for_manytomany (code) and noticed two issues:

1. assert not db_field.remote_field.through._meta.auto_created fails with: "Field[Any, Any]" has no attribute "through" [attr-defined] (code ref)
2. formfield is typed as Any, which can be fixed with an assert/type-override (

   django-stubs/django-stubs/db/models/fields/__init__.pyi

   Lines 180 to 181 in 593d04d

   	# TODO: plugin support
   	def formfield(self, **kwargs) -> Any: ...

   )

@admin.register(MyModel)
class MyModelAdmin(BaseAdminMixin):
    …

    def formfield_for_manytomany(
        self, db_field: "ManyToManyField", request: "Optional[HttpRequest]", **kwargs
    ) -> "ModelMultipleChoiceField":
        """Manually use filter_horizontal for input_recipes.

        This is required due to Django not using a non-auto through model.
        Ref: https://code.djangoproject.com/ticket/12203#comment:22
        """
        if db_field.name == "m2m_with_through":
            assert not db_field.remote_field.through._meta.auto_created

            db = kwargs.get("using")
            kwargs["widget"] = widgets.FilteredSelectMultiple(
                db_field.verbose_name,
                False,  # filter_horizontal
            )
            queryset = self.get_field_queryset(db, db_field, request)
            if queryset is not None:
                kwargs["queryset"] = queryset

            form_field = db_field.formfield(**kwargs)
            if TYPE_CHECKING:
                # assert type as it is not provided via django-stubs yet.
                assert isinstance(form_field, ModelMultipleChoiceField)
            msg = _(
                "Hold down “Control”, or “Command” on a Mac, to select more than one."
            )
            help_text = form_field.help_text
            form_field.help_text = (
                format_lazy("{} {}", help_text, msg) if help_text else msg
            )
            return form_field
        return super().formfield_for_manytomany(db_field, request, **kwargs)

System information

• OS: Arch Linux
• python version: 3.9.9
• django version: 3.2.9
• mypy version: 0.910
• django-stubs version: 1.9.0 / master (593d04d)
• django-stubs-ext version: -

[quevon24]

The problem still exists, if you try to declare a proxy model using the through model, it throws the warning: Name "Audio.panel.through" is not defined

e.g.

class AudioPanel(Audio.panel.through):
    class Meta:
        proxy = True

[tony]

Happens for me as of:

• python: 3.10.x
• django: 3.2.x
• mypy: 1.4.x
• django-stubs: 1.13.x

[flaeppe]

I'm going to close this issue as the attribute error for through should be fixed via #1805 while the formfield hints were improved in #1724 and #1739.

Feel free to open a new issue if you find anything else missing or needing improvements.