Allow dynamic data to be deleted

Fixes #374

AUTHORS

@@ -78,3 +78,4 @@ that much better:
  * jonrscott
  * Alice Zoë Bevan-McGregor
  * Stephen Young
+ * tkloc

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 Changes in dev
 ==============
 
+- Fixed deletion of dynamic data
 - Added support for the $elementMatch operator
 - Added reverse option to SortedListFields
 - Fixed dereferencing - multi directional list dereferencing

mongoengine/document.py

@@ -329,6 +329,15 @@ class DynamicDocument(Document):
     __metaclass__ = TopLevelDocumentMetaclass
     _dynamic = True
 
+    def __delattr__(self, *args, **kwargs):
+        """Deletes the attribute by setting to None and allowing _delta to unset
+        it"""
+        field_name = args[0]
+        if field_name in self._dynamic_fields:
+            setattr(self, field_name, None)
+        else:
+            super(DynamicDocument, self).__delattr__(*args, **kwargs)
+
 
 class DynamicEmbeddedDocument(EmbeddedDocument):
     """A Dynamic Embedded Document class allowing flexible, expandable and

tests/dynamic_document.py

@@ -50,6 +50,33 @@ class DynamicDocTest(unittest.TestCase):
         p = self.Person.objects.get()
         self.assertEquals(p.misc, {'hello': 'world'})
 
+    def test_delete_dynamic_field(self):
+        """Test deleting a dynamic field works"""
+        self.Person.drop_collection()
+        p = self.Person()
+        p.name = "Dean"
+        p.misc = 22
+        p.save()
+
+        p = self.Person.objects.get()
+        p.misc = {'hello': 'world'}
+        p.save()
+
+        p = self.Person.objects.get()
+        self.assertEquals(p.misc, {'hello': 'world'})
+        collection = self.db[self.Person._get_collection_name()]
+        obj = collection.find_one()
+        self.assertEquals(sorted(obj.keys()), ['_cls', '_id', '_types', 'misc', 'name'])
+
+        del(p.misc)
+        p.save()
+
+        p = self.Person.objects.get()
+        self.assertFalse(hasattr(p, 'misc'))
+
+        obj = collection.find_one()
+        self.assertEquals(sorted(obj.keys()), ['_cls', '_id', '_types', 'name'])
+
     def test_dynamic_document_queries(self):
         """Ensure we can query dynamic fields"""
         p = self.Person()