Possible Bug when using exclude on a GenericForeignKey / GenericRelation query.

[Daniel H]

Hi everyone.

I've been using django for almost a year now, but it's my first time posting here.

Anyway, I'm encountering an error which I think might be a bug. I've yet to try and replicate it as I thought posting here would be the better first step, as I might just be doing something incorrectly.

When I try a query with .exclude() on a table with a GenericForeignKey and a reverse Generic Relation on a different table, I get this:

AttributeError at /list
'GenericRelation' object has no attribute 'field'

Here is a mock up of my database structure:

class InternalOffer(models.Model):

    user = models.ForeignKey('User')
    status = models.CharField(max_length=64)

    (more offer data...)

    relation = GenericRelation(OfferJoin, related_query_name='offerquery')

class ExternalOffer(models.Model):

    user = models.ForeignKey('User')
    status = models.CharField(max_length=64)

    (more offer data...)

    relation = GenericRelation(OfferJoin, related_query_name='offerquery')

class OfferJoin(models.Model):

    content_type = models.ForeignKey(ContentType)

    object_id = models.PositiveIntegerField()

    offer = GenericForeignKey('content_type', 'object_id')

I can filter fine, it's only the exclude that causes errors. Here is the code that causes the error:

offers = OfferCover.objects.filter(offerquery__user__id=request.user.id)

offers = offers.exclude(offerquery__status="Completed")

Here's the full callback:

Django Version: 1.8.2

Python Version: 2.7.6

Traceback:

File "/Library/Python/2.7/site-packages/django/core/handlers/base.py" in get_response

  132.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/Library/Python/2.7/site-packages/django/contrib/auth/decorators.py" in _wrapped_view

  22.                 return view_func(request, *args, **kwargs)

File "/Users/path-to-project/project/views.py" in list

  136.     offers = offers.exclude(o__status="Completed")

File "/Library/Python/2.7/site-packages/django/db/models/query.py" in exclude

  686.         return self._filter_or_exclude(True, *args, **kwargs)

File "/Library/Python/2.7/site-packages/django/db/models/query.py" in _filter_or_exclude

  695.             clone.query.add_q(~Q(*args, **kwargs))

File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py" in add_q

  1304.         clause, require_inner = self._add_q(where_part, self.used_aliases)

File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py" in _add_q

  1332.                     allow_joins=allow_joins, split_subq=split_subq,

File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py" in build_filter

  1180.                                       can_reuse, e.names_with_path)

File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py" in split_exclude

  1562.         trimmed_prefix, contains_louter = query.trim_start(names_with_path)

File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py" in trim_start

  1989.         join_field = path.join_field.field

Exception Type: AttributeError at /list

Exception Value: 'GenericRelation' object has no attribute 'field'

I've read the documentation multiple times and haven't come across anything usefull. I know that filtering GFKs alone won't work, but both filtering and excluding should work with the reverse Generic Relation.

Thanks!

- Daniel Harris

[Tim Graham]

The crash is probably a bug: https://code.djangoproject.com/ticket/26261