Merge pull request #1 from emilecaron/fix_delete_rule_cascade_cycle

Fix delete rule cascade cycle

mongoengine/queryset/base.py

@@ -346,7 +346,7 @@ class BaseQuerySet(object):
             return 0
         return self._cursor.count(with_limit_and_skip=with_limit_and_skip)
 
-    def delete(self, write_concern=None, _from_doc_delete=False):
+    def delete(self, write_concern=None, _from_doc_delete=False, cascade_refs=None):
         """Delete the documents matched by the query.
 
         :param write_concern: Extra keyword arguments are passed down which
@@ -363,6 +363,11 @@ class BaseQuerySet(object):
         queryset = self.clone()
         doc = queryset._document
 
+        cascade_refs = set() if cascade_refs is None else cascade_refs
+        if doc in cascade_refs:
+            return 0
+        cascade_refs.add(doc)
+
         if write_concern is None:
             write_concern = {}
 
@@ -404,9 +409,8 @@ class BaseQuerySet(object):
             if rule == CASCADE:
                 ref_q = document_cls.objects(**{field_name + '__in': self})
                 ref_q_count = ref_q.count()
-                if (doc != document_cls and ref_q_count > 0 or
-                        (doc == document_cls and ref_q_count > 0)):
-                    ref_q.delete(write_concern=write_concern)
+                if ref_q_count > 0:
+                    ref_q.delete(write_concern=write_concern, cascade_refs=cascade_refs)
             elif rule == NULLIFY:
                 document_cls.objects(**{field_name + '__in': self}).update(
                     write_concern=write_concern, **{'unset__%s' % field_name: 1})

tests/queryset/queryset.py

@@ -1413,6 +1413,23 @@ class QuerySetTest(unittest.TestCase):
         self.Person.objects(name='Test User').delete()
         self.assertEqual(1, BlogPost.objects.count())
 
+    def test_reverse_delete_rule_cascade_cycle(self):
+        """Ensure reference cascading doesn't loop if reference graph isn't
+        a tree
+        """
+        class Dummy(Document):
+            reference = ReferenceField('self', reverse_delete_rule=CASCADE)
+
+        base = Dummy().save()
+        other = Dummy(reference=base).save()
+        base.reference = other
+        base.save()
+
+        base.delete()
+
+        self.assertRaises(DoesNotExist, base.reload)
+        self.assertRaises(DoesNotExist, other.reload)
+
     def test_reverse_delete_rule_cascade_self_referencing(self):
         """Ensure self-referencing CASCADE deletes do not result in infinite
         loop