DjangoConnectionField triggers django orm sql asserts with complex resolve + filtering

[danyx23]

When a DjangoConnectionField is resolved using a custom method that does nontrivial filtering that involve an inner join and a .distinct() call, then resolving this field with a filter fails. This is because the assert in django/db/models/sql/query.py is triggered when DjangoConnectionField.DjangoConnectionField combines the filtered Queryset with an intersection on the queryset from the custom resolve method.

To give a concrete example, in the following model, the given query fails with an exception:

# Models
class FilmDetails(models.Model):
    location = models.CharField(max_length=30)
    film = models.OneToOneField('Film', related_name='details')


class Film(models.Model):
    genre = models.CharField(max_length=2, help_text='Genre', choices=[
        ('do', 'Documentary'),
        ('ot', 'Other')
    ], default='ot')
    reporters = models.ManyToManyField('Reporter',
                                       related_name='films')

# Graphene-Django classes
class FilmType(DjangoObjectType):
        class Meta:
            model = Film
            interfaces = (Node, )
            filter_fields = ('genre',)

class Query(graphene.ObjectType):
    films = DjangoConnectionField(FilmType)

    def resolve_films(self, args, context, info):
         return Film.objects \
              .filter(
                    Q(details__location__contains="Berlin") | 
                    Q(genre__in=['ot']))
              .distinct()

# Test query
f = Film.objects.create()
fd = FilmDetails.objects.create(
    location="Berlin",
    film=f
)

schema = graphene.Schema(query=Query)
query = '''
        query NodeFilteringQuery {
            films {
                edges {
                    node {
                        genre
                    }
                }
            }
        }
 '''

This was discovered with graphene-django 1.3 on python 3.

[danyx23]

I'll send a PR soon to fix this