From a8598c7de2d600fa4c3b4e6d80c2fafb9063215b Mon Sep 17 00:00:00 2001
From: Ramiro Morales <cramm0@gmail.com>
Date: Sat, 21 May 2011 16:54:25 +0000
Subject: [PATCH] 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                          | 8 ++++++++
 tests/regressiontests/aggregation_regress/tests.py | 7 +++++++
 2 files changed, 15 insertions(+)

diff --git a/django/db/models/query.py b/django/db/models/query.py
index 9c3aeaa8d3a..6a6a82968fd 100644
--- a/django/db/models/query.py
+++ b/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
diff --git a/tests/regressiontests/aggregation_regress/tests.py b/tests/regressiontests/aggregation_regress/tests.py
index 15692b6422d..49e1e611e9e 100644
--- a/tests/regressiontests/aggregation_regress/tests.py
+++ b/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(),