ManyToMany relationships referencing 'self' choke when the model has a non null foreign key

[Nicola Heald]

models:

  class Group(models.Model):
      name = models.CharField(max_length=64)

  class Member(models.Model):
      group = models.ForeignKey(Group)
      name = models.CharField(max_length=64)
      friends = models.ManyToManyField('self', blank=True, symmetrical=False, related_name='buddies')

>>> from django_factory import Factory
>>> f = Factory()
>>> from testapp.models import Member
>>> m = f.make_one(Member)
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/vagrant/Work/django_factory_test/apps/django_factory/factory.py", line 493, in make_one
    return self._create_one(model, True, [], attrs)
  File "/vagrant/Work/django_factory_test/apps/django_factory/factory.py", line 413, in _create_one
    instance, m2m_dict, fk_dict = self._generate_instance(model, save, attrs, not_including)
  File "/vagrant/Work/django_factory_test/apps/django_factory/factory.py", line 283, in _generate_instance
    model, field, not_including, attrs)
  File "/vagrant/Work/django_factory_test/apps/django_factory/factory.py", line 199, in _generate_many_to_many_value
    not_including + [model], {}))
  File "/vagrant/Work/django_factory_test/apps/django_factory/factory.py", line 419, in _create_one
    instance.save()
  File "/usr/lib/pymodules/python2.6/django/db/models/base.py", line 410, in save
    self.save_base(force_insert=force_insert, force_update=force_update)
  File "/usr/lib/pymodules/python2.6/django/db/models/base.py", line 495, in save_base
    result = manager._insert(values, return_id=update_pk)
  File "/usr/lib/pymodules/python2.6/django/db/models/manager.py", line 177, in _insert
    return insert_query(self.model, values, **kwargs)
  File "/usr/lib/pymodules/python2.6/django/db/models/query.py", line 1087, in insert_query
    return query.execute_sql(return_id)
  File "/usr/lib/pymodules/python2.6/django/db/models/sql/subqueries.py", line 320, in execute_sql
    cursor = super(InsertQuery, self).execute_sql(None)
  File "/usr/lib/pymodules/python2.6/django/db/models/sql/query.py", line 2369, in execute_sql
    cursor.execute(sql, params)
  File "/usr/lib/pymodules/python2.6/django/db/backends/util.py", line 19, in execute
    return self.cursor.execute(sql, params)
IntegrityError: null value in column "group_id" violates not-null constraint

What happens is that the member is created, a group is created, and that's fine. Then a member is created to get test data in to the 'friends' field, but none of the foreignkeys are used when generating the member for 'friends'.

[James Westby (james-w)]

Hi, nice bug. The loop detection was broken (over eager) and so it was skipping
the ForeignKey as you identified.

I've fixed the loop detection so it only skips the ForeignKey if it is really part
of a loop.

Thanks,

James