Fix #17876: Corrected an exception (regression) raised where select_realted and only is used on a proxy model. Thanks milosu and charettes.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17692 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/query.py

@@ -1266,7 +1266,7 @@ def get_klass_info(klass, max_depth=0, cur_depth=0, requested=None,
         return None
 
     if only_load:
-        load_fields = only_load.get(klass)
+        load_fields = only_load.get(klass) or set()
         # When we create the object, we will also be creating populating
         # all the parent classes, so traverse the parent classes looking
         # for fields that must be included on load.

tests/modeltests/defer/models.py

@@ -22,3 +22,7 @@ class Child(Primary):
 
 class BigChild(Primary):
     other = models.CharField(max_length=50)
+
+class ChildProxy(Child):
+    class Meta:
+        proxy=True

tests/modeltests/defer/tests.py

@@ -3,7 +3,7 @@ from __future__ import absolute_import
 from django.db.models.query_utils import DeferredAttribute
 from django.test import TestCase
 
-from .models import Secondary, Primary, Child, BigChild
+from .models import Secondary, Primary, Child, BigChild, ChildProxy
 
 
 class DeferTests(TestCase):
@@ -145,3 +145,7 @@ class DeferTests(TestCase):
         obj.name = "bb"
         obj.save()
 
+    def test_defer_proxy(self):
+        # using select related and only should not result in Exception
+        for obj in ChildProxy.objects.all().select_related().only('id'):
+            continue