Fixed #11789 -- Fixed aggregates so it interacts with QuerySet none() in a way…

Fixed #11789 -- Fixed aggregates so it interacts with QuerySet none() in a way consistent with other empty query sets. Thanks alexr for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16254 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/query.py

@@ -1132,6 +1132,14 @@ class EmptyQuerySet(QuerySet):
         """
         return 0
 
+    def aggregate(self, *args, **kwargs):
+        """
+        Return a dict mapping the aggregate names to None
+        """
+        for arg in args:
+            kwargs[arg.default_alias] = arg
+        return dict([(key, None) for key in kwargs])
+
     # EmptyQuerySet is always an empty result in where-clauses (and similar
     # situations).
     value_annotation = False

tests/regressiontests/aggregation_regress/tests.py

@@ -662,6 +662,13 @@ class AggregationTests(TestCase):
             {"pk__count": None}
         )
 
+    def test_none_call_before_aggregate(self):
+        # Regression for #11789
+        self.assertEqual(
+            Author.objects.none().aggregate(Avg('age')),
+            {'age__avg': None}
+        )
+
     def test_annotate_and_join(self):
         self.assertEqual(
             Author.objects.annotate(c=Count("friends__name")).exclude(friends__name="Joe").count(),