Django Filters Extension is unable to handle filter fields with a function method kwarg

[rvinzent]

Describe the bug
Spectacular errors when on the second example from these django-filter docs

The method argument is allowed to be a function and drf-spectacular assumes it is a string, raising this error

    def resolve_filter_field(self, auto_schema, model, filterset_class, field_name, filter_field):
        from django_filters.rest_framework import filters
    
        if isinstance(filter_field, filters.OrderingFilter):
            # only here filter_field.field_name is not the model field name/path
            schema = build_basic_type(OpenApiTypes.STR)
        elif filter_field.method:
>           filter_method = getattr(filterset_class, filter_field.method)
E           TypeError: getattr(): attribute name must be string

To Reproduce
Follow example in docs above

Expected behavior
I expect it to not error here, and be able to handle this valid filter

[rvinzent]

The docs fail to build when using functools.partial due to this error:

.venv/lib/python3.9/site-packages/drf_spectacular/contrib/django_filters.py:57: in resolve_filter_field
    filter_method_hints = typing.get_type_hints(filter_method)
TypeError: functools.partial(<function filter_by_unique_id at 0x10bf3e280>, prefix='SA') is not a module, class, method, or function.

The filters still work correctly.

[tfranzel]

sounds weird, those are the batteries! a functools.partial is a callable thus could be considered a function, and typing.get_type_hints is python stdlib.

with doc you mean schema generation, right?

[rvinzent]

According to this post partial objects are not functions.

Maybe it could try to get the type hints and fall back to something else if that fails?

[tfranzel]

that should do it. i hope that was the last line that could produce uncaught exceptions in django-filters.

[tfranzel]

closing this issue for now. feel free to comment if anything is missing or not working and we will follow-up.