Reverse join in `exclude` fails when GenericRelation is defined on an abstract model

[Steve Bussetti]

Exact same use case and setup as #20378. passing the reverse for a GenericRelation to QuerySet.filter works just fine, but for QuerySet.exclude it fails with AttributeError: 'GenericRelation' object has no attribute 'field'

AttributeError                            Traceback (most recent call last)
<ipython-input-10-0e802368f888> in <module>()
----> 1 Comment.objects.exclude(list_set__comments_enabled=False)

./lib/python2.7/site-packages/django/db/models/manager.pyc in manager_method(self, *args, **kwargs)
    120         def create_method(name, method):
    121             def manager_method(self, *args, **kwargs):
--> 122                 return getattr(self.get_queryset(), name)(*args, **kwargs)
    123             manager_method.__name__ = method.__name__
    124             manager_method.__doc__ = method.__doc__

./lib/python2.7/site-packages/django/db/models/query.pyc in exclude(self, *args, **kwargs)
    795         set.
    796         """
--> 797         return self._filter_or_exclude(True, *args, **kwargs)
    798
    799     def _filter_or_exclude(self, negate, *args, **kwargs):
./lib/python2.7/site-packages/django/db/models/query.pyc in _filter_or_exclude(self, negate, *args, **kwargs)
    804         clone = self._clone()
    805         if negate:
--> 806             clone.query.add_q(~Q(*args, **kwargs))
    807         else:
    808             clone.query.add_q(Q(*args, **kwargs))

./lib/python2.7/site-packages/django/db/models/sql/query.pyc in add_q(self, q_object)
   1241         existing_inner = set(
   1242             (a for a in self.alias_map if self.alias_map[a].join_type == INNER))
-> 1243         clause, _ = self._add_q(q_object, self.used_aliases)
   1244         if clause:
   1245             self.where.add(clause, AND)

./lib/python2.7/site-packages/django/db/models/sql/query.pyc in _add_q(self, q_object, used_aliases, branch_negated, current_negated, allow_joins, split_subq)
   1267                     child, can_reuse=used_aliases, branch_negated=branch_negated,
   1268                     current_negated=current_negated, connector=connector,
-> 1269                     allow_joins=allow_joins, split_subq=split_subq,
   1270                 )
   1271                 joinpromoter.add_votes(needed_inner)

./lib/python2.7/site-packages/django/db/models/sql/query.pyc in build_filter(self, filter_expr, branch_negated, current_negated, can_reuse, connector, allow_joins, split_subq)
   1179         except MultiJoin as e:
   1180             return self.split_exclude(filter_expr, LOOKUP_SEP.join(parts[:e.level]),
-> 1181                                       can_reuse, e.names_with_path)
   1182
   1183         if can_reuse is not None:

./lib/python2.7/site-packages/django/db/models/sql/query.pyc in split_exclude(self, filter_expr, prefix, can_reuse, names_with_path)
   1497         # Try to have as simple as possible subquery -> trim leading joins from
   1498         # the subquery.
-> 1499         trimmed_prefix, contains_louter = query.trim_start(names_with_path)
   1500
   1501         # Add extra check to make sure the selected field will not be null

./lib/python2.7/site-packages/django/db/models/sql/query.pyc in trim_start(self, names_with_path)
   1932             self.unref_alias(alias)
   1933         # The path.join_field is a Rel, lets get the other side's field
-> 1934         join_field = path.join_field.field
   1935         # Build the filter prefix.
   1936         paths_in_prefix = trimmed_paths

AttributeError: 'GenericRelation' object has no attribute 'field'

[Tim Graham]

Looks like a duplicate of #26261. If you want to add an additional regression on that ticket test similar to https://code.djangoproject.com/attachment/ticket/26261/26261-test.diff just to be sure, that would be great.

I'd do it myself but the report is a bit confusing since you say "exact same use case and setup as #20378" but then the example query uses a Comment model which isn't part of that ticket.

[Steve Bussetti]

Yeah, different model names, but otherwise same exact setup. Closing this as a duplicate of #26261 -- there's nothing to add. That's the same issue.