id,summary,reporter,owner,description,type,status,component,version,severity,resolution,keywords,cc,stage,has_patch,needs_docs,needs_tests,needs_better_patch,easy,ui_ux 26605,Abstract model inheriting concrete model crashes migrations,Sébastien Diemer,Ingo Klöcker,"When using Model inheritance with an abstract model in between, it can happen that the _default_manager of the actual child class is None. In this case the //ModelState.from_model// function fails with the following error: {{{ django/django/db/migrations/state.py"", line 439, in from_model default_manager_name = force_text(model._default_manager.name) AttributeError: 'NoneType' object has no attribute 'name' }}} The following modified test reproduces the error: {{{ @override_settings(TEST_SWAPPABLE_MODEL='migrations.SomeFakeModel') def test_create_swappable(self): """""" Tests making a ProjectState from an Apps with a swappable model """""" new_apps = Apps(['migrations']) class Base(models.Model): pass class AbstractAuthor(Base): class Meta: abstract = True class Author(AbstractAuthor): name = models.CharField(max_length=255) bio = models.TextField() age = models.IntegerField(blank=True, null=True) class Meta(AbstractAuthor.Meta): app_label = 'migrations' apps = new_apps swappable = 'TEST_SWAPPABLE_MODEL' author_state = ModelState.from_model(Author) self.assertEqual(author_state.app_label, 'migrations') self.assertEqual(author_state.name, 'Author') self.assertEqual([x for x, y in author_state.fields], ['id', 'name', 'bio', 'age']) self.assertEqual(author_state.fields[1][1].max_length, 255) self.assertEqual(author_state.fields[2][1].null, False) self.assertEqual(author_state.fields[3][1].null, True) self.assertEqual(author_state.options, {'abstract': False, 'swappable': 'TEST_SWAPPABLE_MODEL'}) self.assertEqual(author_state.bases, (models.Model, )) self.assertEqual(author_state.managers, []) }}} Changing the following line in //ModelState.from_model// {{{ if hasattr(model, ""_default_manager""): }}} to {{{ if getattr(model, ""_default_manager"", None): }}} is probably sufficient to fix the bug. See also PR https://github.com/django/django/pull/6847",Bug,closed,Migrations,1.8,Normal,fixed,,diemersebastien@…,Accepted,1,0,1,0,0,0