Wrap saving operations in a transaction

Wrap saving operations in a transaction to prevent inconsistency between main model and closure model

closuretree/models.py

@@ -26,7 +26,7 @@
 # Public methods are useful!
 # pylint: disable=R0904
 
-from django.db import models
+from django.db import models, transaction
 from django.db.models.base import ModelBase
 from django.db.models.signals import post_save, pre_delete
 from django.dispatch import receiver
@@ -116,6 +116,17 @@ def __setattr__(self, name, value):
                 self._closure_change_init()
         super(ClosureModel, self).__setattr__(name, value)
 
+    def save_base(self, *args, **kwargs):
+        """Wrap the saving operation of this model and that of the closure
+            table in one transaction.
+        """
+        # the superclass save_base() sends post_save() signal.
+        # post_save() is then received by closure_model_save() function,
+        # which saves closure model.
+        # we're going to wrap this series of operations in a transaction.
+        with transaction.atomic():
+            super(ClosureModel, self).save_base(*args, **kwargs)
+
     @classmethod
     def _toplevel(cls):
         """Find the top level of the chain we're in.

closuretree/tests.py

@@ -24,8 +24,9 @@
 # pylint: disable=
 
 from django import VERSION
-from django.test import TestCase
+from django.test import TestCase, TransactionTestCase
 from django.db import models
+from django.db.utils import IntegrityError
 from closuretree.models import ClosureModel
 import uuid
 
@@ -118,6 +119,54 @@ def test_deletion(self):
         self.b.delete()
         self.failUnlessEqual(self.closure_model.objects.count(), 2)
 
+class DirtyParentTestCase(TransactionTestCase):
+
+    normal_model = TC
+    closure_model = TCClosure
+
+    def setUp(self):
+        self.a = self.normal_model.objects.create(name="a")
+        self.b = self.normal_model.objects.create(name="b")
+        self.c = self.normal_model.objects.create(name="c")
+        self.d = self.normal_model.objects.create(name="d")
+
+    def test_selfreferencing_parent(self):
+        """Tests that instances with self-referencing parents are not saved"""
+        self.b.parent2 = self.a
+        self.b.save()
+        self.c.parent2 = self.b
+        self.c.save()
+
+        # this is the prerequisite of this test:
+        # closure model contains 7 rows before we save dirty data
+        self.assertEqual(self.closure_model.objects.count(), 7)
+
+        # dirty data
+        self.b.parent2 = self.b
+        # save dirty data
+        self.assertRaises(IntegrityError, self.b.save)
+
+        # closure model contains the same number of data as before
+        self.assertEqual(self.closure_model.objects.count(), 7)
+
+    def test_parent_referencing_child(self):
+        """Tests instances with circular-referencing parents are not saved"""
+        self.b.parent2 = self.a
+        self.b.save()
+        self.c.parent2 = self.b
+        self.c.save()
+
+        # this is the prerequisite of this test:
+        # closure model contains 7 rows before we save dirty data
+        self.assertEqual(self.closure_model.objects.count(), 7)
+
+        # dirty data
+        self.b.parent2 = self.c
+        # save dirty data
+        self.assertRaises(IntegrityError, self.b.save)
+
+        # closure model contains the same number of data as before
+        self.assertEqual(self.closure_model.objects.count(), 7)
 
 if VERSION >= (1, 8):
     class UUIDTC(ClosureModel):