Fix #13864: Removed database error raised when force_update is requsted on save of an inherited model with no fields of its own. Thanks fva, gregmuellegger, and markb1.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17088 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/modeltests/force_insert_update/tests.py

@@ -3,14 +3,15 @@ from __future__ import absolute_import
 from django.db import transaction, IntegrityError, DatabaseError
 from django.test import TestCase
 
-from .models import Counter, WithCustomPK
+from .models import (Counter, WithCustomPK, InheritedCounter, ProxyCounter,
+                     SubCounter)
 
 
 class ForceTests(TestCase):
     def test_force_update(self):
         c = Counter.objects.create(name="one", value=1)
-        # The normal case
 
+        # The normal case
         c.value = 2
         c.save()
         # Same thing, via an update
@@ -38,3 +39,25 @@ class ForceTests(TestCase):
         # the data isn't in the database already.
         obj = WithCustomPK(name=1, value=1)
         self.assertRaises(DatabaseError, obj.save, force_update=True)
+
+
+class InheritanceTests(TestCase):
+    def test_force_update_on_inherited_model(self):
+        a = InheritedCounter(name="count", value=1, tag="spam")
+        a.save()
+        a.save(force_update=True)
+
+    def test_force_update_on_proxy_model(self):
+        a = ProxyCounter(name="count", value=1)
+        a.save()
+        a.save(force_update=True)
+
+    def test_force_update_on_inherited_model_without_fields(self):
+        '''
+        Issue 13864: force_update fails on subclassed models, if they don't
+        specify custom fields.
+        '''
+        a = SubCounter(name="count", value=1)
+        a.save()
+        a.value = 2
+        a.save(force_update=True)