AttributeError | 'NoneType' object has no attribute 'attname'

[InzGIBA]

An error occurs when deleting a primary object. Where polymorphic is a foreign key

Spec

Request Method: POST
Django Version: 3.1.7
Exception Type: AttributeError
Exception Value: 'NoneType' object has no attribute 'attname'
Python Version: 3.9.2

Traceback (most recent call last):

  File "/usr/local/lib/python3.9/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.9/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/contrib/admin/options.py", line 614, in wrapper
    return self.admin_site.admin_view(view)(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/views/decorators/cache.py", line 44, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/contrib/admin/sites.py", line 233, in inner
    return view(request, *args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/utils/decorators.py", line 43, in _wrapper
    return bound_method(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/contrib/admin/options.py", line 1735, in changelist_view
    response = self.response_action(request, queryset=cl.get_queryset(request))
  File "/usr/local/lib/python3.9/site-packages/django/contrib/admin/options.py", line 1402, in response_action
    response = func(self, request, queryset)
  File "/usr/local/lib/python3.9/site-packages/django/contrib/admin/actions.py", line 40, in delete_selected
    modeladmin.delete_queryset(request, queryset)
  File "/usr/local/lib/python3.9/site-packages/django/contrib/admin/options.py", line 1103, in delete_queryset
    queryset.delete()
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 746, in delete
    collector.collect(del_query)
  File "/usr/local/lib/python3.9/site-packages/django/db/models/deletion.py", line 295, in collect
    if sub_objs:
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 291, in __bool__
    self._fetch_all()
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 1308, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/usr/local/lib/python3.9/site-packages/polymorphic/query.py", line 64, in _polymorphic_iterator
    real_results = self.queryset._get_real_instances(base_result_objects)
  File "/usr/local/lib/python3.9/site-packages/polymorphic/query.py", line 387, in _get_real_instances
    if base_object.polymorphic_ctype_id == self_model_class_id:
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query_utils.py", line 149, in __get__
    instance.refresh_from_db(fields=[field_name])
  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 635, in refresh_from_db
    db_instance = db_instance_qs.get()
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 425, in get
    num = len(clone)
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 269, in __len__
    self._fetch_all()
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 1308, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/usr/local/lib/python3.9/site-packages/polymorphic/query.py", line 64, in _polymorphic_iterator
    real_results = self.queryset._get_real_instances(base_result_objects)
  File "/usr/local/lib/python3.9/site-packages/polymorphic/query.py", line 460, in _get_real_instances
    real_objects_dict = {
  File "/usr/local/lib/python3.9/site-packages/polymorphic/query.py", line 461, in <dictcomp>
    getattr(real_object, pk_name): real_object
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query_utils.py", line 147, in __get__
    val = self._check_parent_chain(instance)
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query_utils.py", line 163, in _check_parent_chain
    return getattr(instance, link_field.attname)

[AdamDonna]

Hey @InzGIBA do you have capacity to write a failing unit test for this? It sounds like sensible behaviour for this package to support