From 823cf421fac4bd1a20b3b10bd4347b74e7bcf857 Mon Sep 17 00:00:00 2001
From: Ross Lawley <ross.lawley@gmail.com>
Date: Thu, 29 Sep 2011 14:07:30 -0700
Subject: [PATCH] Fixes to circular references.

Removes infinite looping
refs #294
---
 mongoengine/dereference.py |  6 ++--
 tests/dereference.py       | 59 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/mongoengine/dereference.py b/mongoengine/dereference.py
index 7fe9ba2f..949bb2f9 100644
--- a/mongoengine/dereference.py
+++ b/mongoengine/dereference.py
@@ -33,13 +33,15 @@ class DeReference(object):
             items = [i for i in items]
 
         self.max_depth = max_depth
-        
+
         doc_type = None
         if instance and instance._fields:
             doc_type = instance._fields[name].field
-    
+
             if isinstance(doc_type, ReferenceField):
                 doc_type = doc_type.document_type
+                if all([i.__class__ == doc_type for i in items]):
+                    return items
 
         self.reference_map = self._find_references(items)
         self.object_map = self._fetch_objects(doc_type=doc_type)
diff --git a/tests/dereference.py b/tests/dereference.py
index a98267fd..b85ca179 100644
--- a/tests/dereference.py
+++ b/tests/dereference.py
@@ -129,6 +129,65 @@ class FieldTest(unittest.TestCase):
                 self.assertEquals(employee.friends, friends)
                 self.assertEqual(q, 2)
 
+    def test_circular_reference(self):
+        """Ensure you can handle circular references
+        """
+        class Person(Document):
+            name = StringField()
+            relations = ListField(EmbeddedDocumentField('Relation'))
+
+            def __repr__(self):
+                return "<Person: %s>" % self.name
+
+        class Relation(EmbeddedDocument):
+            name = StringField()
+            person = ReferenceField('Person')
+
+        Person.drop_collection()
+        mother = Person(name="Mother")
+        daughter = Person(name="Daughter")
+
+        mother.save()
+        daughter.save()
+
+        daughter_rel = Relation(name="Daughter", person=daughter)
+        mother.relations.append(daughter_rel)
+        mother.save()
+
+        mother_rel = Relation(name="Daughter", person=mother)
+        self_rel = Relation(name="Self", person=daughter)
+        daughter.relations.append(mother_rel)
+        daughter.relations.append(self_rel)
+        daughter.save()
+
+        self.assertEquals("[<Person: Mother>, <Person: Daughter>]", "%s" % Person.objects())
+
+    def test_circular_reference_on_self(self):
+        """Ensure you can handle circular references
+        """
+        class Person(Document):
+            name = StringField()
+            relations = ListField(ReferenceField('self'))
+
+            def __repr__(self):
+                return "<Person: %s>" % self.name
+
+        Person.drop_collection()
+        mother = Person(name="Mother")
+        daughter = Person(name="Daughter")
+
+        mother.save()
+        daughter.save()
+
+        mother.relations.append(daughter)
+        mother.save()
+
+        daughter.relations.append(mother)
+        daughter.relations.append(daughter)
+        daughter.save()
+
+        self.assertEquals("[<Person: Mother>, <Person: Daughter>]", "%s" % Person.objects())
+
     def test_generic_reference(self):
 
         class UserA(Document):