From d15b256ce4a123fc932f720f5a3303c1a700ab91 Mon Sep 17 00:00:00 2001
From: Clayton Parker <clayton@sixfeetup.com>
Date: Sun, 9 Feb 2014 14:21:20 -0600
Subject: [PATCH] fix serialization of default with drop

fixes #139
---
 CHANGES.txt                     |  3 +++
 colander/__init__.py            | 22 ++++++++++++----------
 colander/tests/test_colander.py | 10 ++++++++++
 3 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 2c5fa12..e2f41df 100644
--- a/CHANGES.txt
+++ b/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
 ~~~~~~~~
diff --git a/colander/__init__.py b/colander/__init__.py
index 4773b68..4104863 100644
--- a/colander/__init__.py
+++ b/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:
-                try:
-                    sub_result = callback(subnode, subval)
-                except Invalid as e:
-                    if error is None:
-                        error = Invalid(node)
-                    error.add(e, num)
-                else:
-                    if sub_result is not drop:
-                        result[name] = sub_result
+            if subval is drop or (subval is null and subnode.default is drop):
+                continue
+            try:
+                sub_result = callback(subnode, subval)
+            except Invalid as e:
+                if error is None:
+                    error = Invalid(node)
+                error.add(e, num)
+            else:
+                if sub_result is drop:
+                    continue
+                result[name] = sub_result
 
         if self.unknown == 'raise':
             if value:
diff --git a/colander/tests/test_colander.py b/colander/tests/test_colander.py
index 2ec5c0a..bf6e6fc 100644
--- a/colander/tests/test_colander.py
+++ b/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