Merge pull request #167 from claytron/issue_139_default_drop

fix serialization of default with drop

CHANGES.txt

@@ -9,6 +9,9 @@ Bug Fixes
 - Set the max length TLD to 22 in ``Email`` validator based on the
   current list of valid TLDs.
   See https://github.com/Pylons/colander/issues/159
+- Fix an issue where ``drop`` was not recognized as a default and was
+  returning the ``drop`` instance instead of omitting the value.
+  https://github.com/Pylons/colander/issues/139
 
 Features
 ~~~~~~~~

colander/__init__.py

@@ -572,16 +572,18 @@ class Mapping(SchemaType):
         for num, subnode in enumerate(node.children):
             name = subnode.name
             subval = value.pop(name, null)
-            if subval is not drop:
+            if subval is drop or (subval is null and subnode.default is drop):
-                try:
+                continue
-                    sub_result = callback(subnode, subval)
+            try:
-                except Invalid as e:
+                sub_result = callback(subnode, subval)
-                    if error is None:
+            except Invalid as e:
-                        error = Invalid(node)
+                if error is None:
-                    error.add(e, num)
+                    error = Invalid(node)
-                else:
+                error.add(e, num)
-                    if sub_result is not drop:
+            else:
-                        result[name] = sub_result
+                if sub_result is drop:
+                    continue
+                result[name] = sub_result
 
         if self.unknown == 'raise':
             if value:

colander/tests/test_colander.py

@@ -3153,6 +3153,16 @@ class TestSchema(unittest.TestCase):
         result = node.deserialize(expected)
         self.assertEqual(result, expected)
 
+    def test_serialize_drop_default(self):
+        import colander
+        class MySchema(colander.Schema):
+            a = colander.SchemaNode(colander.String())
+            b = colander.SchemaNode(colander.String(), default=colander.drop)
+        node = MySchema()
+        expected = {'a': 'foo'}
+        result = node.serialize(expected)
+        self.assertEqual(result, expected)
+
 class TestSequenceSchema(unittest.TestCase):
     def test_succeed(self):
         import colander