Fixed issue with dynamic documents deltas

Closes #377

AUTHORS

@@ -82,3 +82,4 @@ that much better:
  * aid
  * yamaneko1212
  * dave mankoff
+ * Alexander G. Morano

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 Changes in dev
 ==============
 
+- Fixed issue with dynamic documents deltas
 - Added Reverse Delete Rule support to ListFields - MapFields aren't supported
 - Added customisable cascade kwarg options
 - Fixed Handle None values for non-required fields

mongoengine/base.py

@@ -954,6 +954,7 @@ class BaseDocument(object):
         set_fields = self._get_changed_fields()
         set_data = {}
         unset_data = {}
+        parts = []
         if hasattr(self, '_changed_fields'):
             set_data = {}
             # Fetch each set item from its path
@@ -980,7 +981,7 @@ class BaseDocument(object):
 
             # If we've set a value that ain't the default value dont unset it.
             default = None
-            if self._dynamic and parts[0] in self._dynamic_fields:
+            if self._dynamic and len(parts) and parts[0] in self._dynamic_fields:
                 del(set_data[path])
                 unset_data[path] = 1
                 continue

tests/dynamic_document.py

@@ -36,6 +36,15 @@ class DynamicDocTest(unittest.TestCase):
         # Confirm no changes to self.Person
         self.assertFalse(hasattr(self.Person, 'age'))
 
+    def test_dynamic_document_delta(self):
+        """Ensures simple dynamic documents can delta correctly"""
+        p = self.Person(name="James", age=34)
+        self.assertEquals(p._delta(), ({'_types': ['Person'], 'age': 34, 'name': 'James', '_cls': 'Person'}, {}))
+
+        p.doc = 123
+        del(p.doc)
+        self.assertEquals(p._delta(), ({'_types': ['Person'], 'age': 34, 'name': 'James', '_cls': 'Person'}, {'doc': 1}))
+
     def test_change_scope_of_variable(self):
         """Test changing the scope of a dynamic field has no adverse effects"""
         p = self.Person()