Ticket #7918: subclass-foreignkey.patch

django/db/models/fields/related.py

@@ -225 +225 @@
             val = getattr(instance, self.field.attname)
             if val is None:
                 # If NULL is an allowed value, return it.
-                if self.field.null:
+                if self.field.null or isinstance(self.field,OneToOneField):
                     return None
                 raise self.field.rel.to.DoesNotExist
             other_field = self.field.rel.get_related_field()

django/newforms/models.py

@@ -436 +436 @@
             raise Exception("%s has no field named '%s'" % (model, fk_name))
     else:
         # Try to discover what the ForeignKey from model to parent_model is
-        fks_to_parent = [f for f in opts.fields if isinstance(f, ForeignKey) and f.rel.to == parent_model]
+        fks_to_parent = [f for f in opts.fields if isinstance(f, ForeignKey) and issubclass(parent_model,f.rel.to)]
         if len(fks_to_parent) == 1:
             fk = fks_to_parent[0]
         elif len(fks_to_parent) == 0: