Fixed inconsistency handling None values field attrs

fixes hmarr/mongoengine#505

docs/changelog.rst

@@ -4,6 +4,7 @@ Changelog
 
 Changes in 0.6.X
 ================
+- Fixed inconsistency handling None values field attrs
 - Fixed map_field embedded db_field issue
 - Fixed .save() _delta issue with DbRefs
 - Fixed Django TestCase

mongoengine/base.py

@@ -833,13 +833,6 @@ class BaseDocument(object):
                 if hasattr(self, '_changed_fields'):
                     self._mark_as_changed(name)
 
-        # Handle None values for required fields
-        if value is None and name in getattr(self, '_fields', {}):
-            self._data[name] = value
-            if hasattr(self, '_changed_fields'):
-                self._mark_as_changed(name)
-            return
-
         if not self._created and name in self._meta.get('shard_key', tuple()):
             from queryset import OperationError
             raise OperationError("Shard Keys are immutable. Tried to update %s" % name)

mongoengine/fields.py

@@ -369,7 +369,7 @@ class ComplexDateTimeField(StringField):
         return self._convert_from_string(data)
 
     def __set__(self, instance, value):
-        value = self._convert_from_datetime(value)
+        value = self._convert_from_datetime(value) if value else value
         return super(ComplexDateTimeField, self).__set__(instance, value)
 
     def validate(self, value):

tests/test_fields.py

@@ -82,7 +82,6 @@ class FieldTest(unittest.TestCase):
 
         # Retrive data from db and verify it.
         ret = HandleNoneFields.objects.all()[0]
-
         self.assertEqual(ret.str_fld, None)
         self.assertEqual(ret.int_fld, None)
         self.assertEqual(ret.flt_fld, None)