Ticket #10237: m2m-inheritance.diff

django/db/models/fields/related.py

@@ -558 +558 @@
             model=rel_model,
             core_filters={'%s__pk' % self.field.related_query_name(): instance._get_pk_val()},
             instance=instance,
-            symmetrical=(self.field.rel.symmetrical and instance.__class__ == rel_model),
+            symmetrical=(self.field.rel.symmetrical and isinstance(instance, rel_model)),
             join_table=qn(self.field.m2m_db_table()),
             source_col_name=qn(self.field.m2m_column_name()),
             target_col_name=qn(self.field.m2m_reverse_name())

tests/regressiontests/m2m_regress/models.py

@@ -26 +26 @@
     def __unicode__(self):
         return self.name
 
+# Two models both inheriting from a base model with a self-referential m2m field
+class SelfReferChild(SelfRefer):
+    pass
+
+class SelfReferChildSibling(SelfRefer):
+    pass
+
 __test__ = {"regressions": """
 # Multiple m2m references to the same model or a different model must be
 # distinguished when accessing the relations through an instance attribute.
@@ -57 +64 @@
 >>> SelfRefer.objects.filter(porcupine='fred')
 Traceback (most recent call last):
 ...
-FieldError: Cannot resolve keyword 'porcupine' into field. Choices are: id, name, references, related
+FieldError: Cannot resolve keyword 'porcupine' into field. Choices are: id, name, references, related, selfreferchild, selfreferchildsibling
+
+# Test to ensure that the relationship between two inherited models
+# with a self-referential m2m field maintains symmetry
+>>> sr_child = SelfReferChild(name="Hanna")
+>>> sr_child.save()
+
+>>> sr_sibling = SelfReferChildSibling(name="Beth")
+>>> sr_sibling.save()
+>>> sr_child.related.add(sr_sibling)
+>>> sr_child.related.all()
+[<SelfRefer: Beth>]
+>>> sr_sibling.related.all()
+[<SelfRefer: Hanna>]
 
 """
 }