--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/parts/django/tests/modeltests/delete/tests.py	Sat Jan 08 11:20:57 2011 +0530
@@ -0,0 +1,135 @@
+from django.db.models import sql
+from django.db.models.loading import cache
+from django.db.models.query import CollectedObjects
+from django.db.models.query_utils import CyclicDependency
+from django.test import TestCase
+
+from models import A, B, C, D, E, F
+
+
+class DeleteTests(TestCase):
+    def clear_rel_obj_caches(self, *models):
+        for m in models:
+            if hasattr(m._meta, '_related_objects_cache'):
+                del m._meta._related_objects_cache
+
+    def order_models(self, *models):
+        cache.app_models["delete"].keyOrder = models
+
+    def setUp(self):
+        self.order_models("a", "b", "c", "d", "e", "f")
+        self.clear_rel_obj_caches(A, B, C, D, E, F)
+
+    def tearDown(self):
+        self.order_models("a", "b", "c", "d", "e", "f")
+        self.clear_rel_obj_caches(A, B, C, D, E, F)
+
+    def test_collected_objects(self):
+        g = CollectedObjects()
+        self.assertFalse(g.add("key1", 1, "item1", None))
+        self.assertEqual(g["key1"], {1: "item1"})
+
+        self.assertFalse(g.add("key2", 1, "item1", "key1"))
+        self.assertFalse(g.add("key2", 2, "item2", "key1"))
+
+        self.assertEqual(g["key2"], {1: "item1", 2: "item2"})
+
+        self.assertFalse(g.add("key3", 1, "item1", "key1"))
+        self.assertTrue(g.add("key3", 1, "item1", "key2"))
+        self.assertEqual(g.ordered_keys(), ["key3", "key2", "key1"])
+
+        self.assertTrue(g.add("key2", 1, "item1", "key3"))
+        self.assertRaises(CyclicDependency, g.ordered_keys)
+
+    def test_delete(self):
+        ## Second, test the usage of CollectedObjects by Model.delete()
+
+        # Due to the way that transactions work in the test harness, doing
+        # m.delete() here can work but fail in a real situation, since it may
+        # delete all objects, but not in the right order. So we manually check
+        # that the order of deletion is correct.
+
+        # Also, it is possible that the order is correct 'accidentally', due
+        # solely to order of imports etc.  To check this, we set the order that
+        # 'get_models()' will retrieve to a known 'nice' order, and then try
+        # again with a known 'tricky' order.  Slightly naughty access to
+        # internals here :-)
+
+        # If implementation changes, then the tests may need to be simplified:
+        #  - remove the lines that set the .keyOrder and clear the related
+        #    object caches
+        #  - remove the second set of tests (with a2, b2 etc)
+
+        a1 = A.objects.create()
+        b1 = B.objects.create(a=a1)
+        c1 = C.objects.create(b=b1)
+        d1 = D.objects.create(c=c1, a=a1)
+
+        o = CollectedObjects()
+        a1._collect_sub_objects(o)
+        self.assertEqual(o.keys(), [D, C, B, A])
+        a1.delete()
+
+        # Same again with a known bad order
+        self.order_models("d", "c", "b", "a")
+        self.clear_rel_obj_caches(A, B, C, D)
+
+        a2 = A.objects.create()
+        b2 = B.objects.create(a=a2)
+        c2 = C.objects.create(b=b2)
+        d2 = D.objects.create(c=c2, a=a2)
+
+        o = CollectedObjects()
+        a2._collect_sub_objects(o)
+        self.assertEqual(o.keys(), [D, C, B, A])
+        a2.delete()
+
+    def test_collected_objects_null(self):
+        g = CollectedObjects()
+        self.assertFalse(g.add("key1", 1, "item1", None))
+        self.assertFalse(g.add("key2", 1, "item1", "key1", nullable=True))
+        self.assertTrue(g.add("key1", 1, "item1", "key2"))
+        self.assertEqual(g.ordered_keys(), ["key1", "key2"])
+
+    def test_delete_nullable(self):
+        e1 = E.objects.create()
+        f1 = F.objects.create(e=e1)
+        e1.f = f1
+        e1.save()
+
+        # Since E.f is nullable, we should delete F first (after nulling out
+        # the E.f field), then E.
+
+        o = CollectedObjects()
+        e1._collect_sub_objects(o)
+        self.assertEqual(o.keys(), [F, E])
+
+        # temporarily replace the UpdateQuery class to verify that E.f is
+        # actually nulled out first
+
+        logged = []
+        class LoggingUpdateQuery(sql.UpdateQuery):
+            def clear_related(self, related_field, pk_list, using):
+                logged.append(related_field.name)
+                return super(LoggingUpdateQuery, self).clear_related(related_field, pk_list, using)
+        original = sql.UpdateQuery
+        sql.UpdateQuery = LoggingUpdateQuery
+
+        e1.delete()
+        self.assertEqual(logged, ["f"])
+        logged = []
+
+        e2 = E.objects.create()
+        f2 = F.objects.create(e=e2)
+        e2.f = f2
+        e2.save()
+
+        # Same deal as before, though we are starting from the other object.
+        o = CollectedObjects()
+        f2._collect_sub_objects(o)
+        self.assertEqual(o.keys(), [F, E])
+        f2.delete()
+        self.assertEqual(logged, ["f"])
+        logged = []
+
+        sql.UpdateQuery = original