Ticket #19089: 19089.patch

django/db/models/fields/related.py

@@ -261 +261 @@
         try:
             rel_obj = getattr(instance, self.cache_name)
         except AttributeError:
-            params = {'%s__pk' % self.related.field.name: instance._get_pk_val()}
-            try:
-                rel_obj = self.get_query_set(instance=instance).get(**params)
-            except self.related.model.DoesNotExist:
+            related_pk = instance._get_pk_val()
+            if related_pk is None:
                 rel_obj = None
             else:
-                setattr(rel_obj, self.related.field.get_cache_name(), instance)
+                params = {'%s__pk' % self.related.field.name: related_pk}
+                try:
+                    rel_obj = self.get_query_set(instance=instance).get(**params)
+                except self.related.model.DoesNotExist:
+                    rel_obj = None
+                else:
+                    setattr(rel_obj, self.related.field.get_cache_name(), instance)
             setattr(instance, self.cache_name, rel_obj)
         if rel_obj is None:
             raise self.related.model.DoesNotExist

tests/regressiontests/one_to_one_regress/tests.py

@@ -202 +202 @@
         with self.assertNumQueries(0):
             with self.assertRaises(UndergroundBar.DoesNotExist):
                 self.p1.undergroundbar
+
+    def test_reverse_with_related_unset_and_single_related_object(self):
+        b = UndergroundBar()
+        b.save()
+        p = Place()
+        with self.assertRaises(UndergroundBar.DoesNotExist):
+            p.undergroundbar