Merge branch 'master' into dev

Conflicts:
	AUTHORS
	docs/changelog.rst
	mongoengine/base.py

AUTHORS

@@ -71,3 +71,4 @@ that much better:
  * Paul Aliagas
  * Paul Cunnane
  * Julien Rebetez
+

docs/changelog.rst

@@ -2,12 +2,10 @@
 Changelog
 =========
 
-
 Changes in dev
 ==============
 
 - Fixed calling a queryset after drop_collection now recreates the collection
-- Fixed tree based circular reference bug
 - Add field name to validation exception messages
 - Added UUID field
 - Improved efficiency of .get()
@@ -16,6 +14,12 @@ Changes in dev
 - Fixed ListField so it doesnt accept strings
 - Added DynamicDocument and EmbeddedDynamicDocument classes for expando schemas
 
+Changes in v0.5.2
+=================
+
+- A Robust Circular reference bugfix
+
+
 Changes in v0.5.1
 =================
 

mongoengine/__init__.py

@@ -14,7 +14,7 @@ __all__ = (document.__all__ + fields.__all__ + connection.__all__ +
 
 __author__ = 'Harry Marr'
 
-VERSION = (0, 5, 1)
+VERSION = (0, 5, 2)
 
 
 def get_version():

mongoengine/base.py

@@ -848,11 +848,11 @@ class BaseDocument(object):
         _changed_fields = []
         _changed_fields += getattr(self, '_changed_fields', [])
 
-        inspected = inspected or []
+        inspected = inspected or set()
         if hasattr(self, 'id'):
             if self.id in inspected:
                 return _changed_fields
-            inspected.append(self.id)
+            inspected.add(self.id)
 
         field_list = self._fields.copy()
         if self._dynamic:
@@ -865,7 +865,7 @@ class BaseDocument(object):
             if hasattr(field, 'id'):
                 if field.id in inspected:
                     continue
-                inspected.append(field.id)
+                inspected.add(field.id)
 
             if isinstance(field, (EmbeddedDocument, DynamicEmbeddedDocument)) and db_field_name not in _changed_fields:  # Grab all embedded fields that have been changed
                 _changed_fields += ["%s%s" % (key, k) for k in field._get_changed_fields(key, inspected) if k]