Ticket #18153: 18153.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_on_unsaved_object_nullable(self):
+        """
+        Regression for #18153 and #19089.
+
+        Accessing the reverse relation on an unsaved object
+        always raises an exception.
+        """
+        p = Place()
+
+        # When there's no instance of the origin of the one-to-one
+        with self.assertRaises(UndergroundBar.DoesNotExist):
+            p.undergroundbar
+
+        UndergroundBar.objects.create()
+
+        # When there's one instance of the origin
+        # (p.undergroundbar used to return that instance)
+        with self.assertRaises(UndergroundBar.DoesNotExist):
+            p.undergroundbar
+
+        UndergroundBar.objects.create()
+
+        # When there are several instances of the origin
+        with self.assertRaises(UndergroundBar.DoesNotExist):
+            p.undergroundbar