From 2d03cd7290b95f0df97f2aa46dd4ceaf22d39211 Mon Sep 17 00:00:00 2001
From: Thomas Adamcik <thomas@adamcik.no>
Date: Sat, 4 Apr 2015 16:22:59 +0200
Subject: [PATCH] models: Make fields handle unsetting defaults in __dict__

---
 mopidy/models.py            | 12 +++++-------
 tests/models/test_fields.py |  8 ++++++++
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/mopidy/models.py b/mopidy/models.py
index 9a22b846..cf11b4d2 100644
--- a/mopidy/models.py
+++ b/mopidy/models.py
@@ -45,13 +45,13 @@ class Field(object):
         return instance.__dict__.get(self._name, self._default)
 
     def __set__(self, instance, value):
-        if value is None:
-            value = self._default
-        value = self.validate(value)
         if value is not None:
-            instance.__dict__[self._name] = value
-        else:
+            value = self.validate(value)
+
+        if value is None or value == self._default:
             self.__delete__(instance)
+        else:
+            instance.__dict__[self._name] = value
 
     def __delete__(self, instance):
         instance.__dict__.pop(self._name, None)
@@ -146,8 +146,6 @@ class ImmutableObject(object):
                 raise TypeError(
                     '__init__() got an unexpected keyword argument "%s"' %
                     key)
-            if value == getattr(self, key):
-                continue  # Don't explicitly set default values
             super(ImmutableObject, self).__setattr__(key, value)
 
     def __setattr__(self, name, value):
diff --git a/tests/models/test_fields.py b/tests/models/test_fields.py
index f2b55f01..864373a9 100644
--- a/tests/models/test_fields.py
+++ b/tests/models/test_fields.py
@@ -59,6 +59,14 @@ class FieldDescriptorTest(unittest.TestCase):
         self.assertEqual(None, instance.attr)
         self.assertNotIn('attr', instance.__dict__)
 
+    def test_field_can_be_set_default(self):
+        default = object()
+        instance = create_instance(Field(default=default))
+        instance.attr = 1234
+        instance.attr = default
+        self.assertEqual(default, instance.attr)
+        self.assertNotIn('attr', instance.__dict__)
+
 
 class FieldTest(unittest.TestCase):
     def test_default_handling(self):