Add support for partial serializer updates

3 files changed, 16 insertions, 3 deletions

diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 01cf5ae3..d35e918c 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -148,7 +148,7 @@ class WritableField(Field):
         self.widget = widget
 
     def validate(self, value):
-        if value in validators.EMPTY_VALUES and self.required:
+        if value in validators.EMPTY_VALUES and self.required and not self.root.partial:
             raise ValidationError(self.error_messages['required'])
 
     def run_validators(self, value):
@@ -186,7 +186,7 @@ class WritableField(Field):
             if self.default is not None:
                 native = self.default
             else:
-                if self.required:
+                if self.required and not self.root.partial:
                     raise ValidationError(self.error_messages['required'])
                 return
 
diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index 2e7e2cf5..229c1b2c 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -91,12 +91,13 @@ class BaseSerializer(Field):
     _options_class = SerializerOptions
     _dict_class = SortedDictWithMetadata  # Set to unsorted dict for backwards compatibility with unsorted implementations.
 
-    def __init__(self, instance=None, data=None, files=None, context=None, **kwargs):
+    def __init__(self, instance=None, data=None, files=None, context=None, partial=False, **kwargs):
         super(BaseSerializer, self).__init__(**kwargs)
         self.opts = self._options_class(self.Meta)
         self.fields = copy.deepcopy(self.base_fields)
         self.parent = None
         self.root = None
+        self.partial = partial
 
         self.context = context or {}
 
diff --git a/rest_framework/tests/serializer.py b/rest_framework/tests/serializer.py
index d522ef97..882f769c 100644
--- a/rest_framework/tests/serializer.py
+++ b/rest_framework/tests/serializer.py
@@ -108,6 +108,18 @@ class BasicTests(TestCase):
         self.assertTrue(serializer.object is expected)
         self.assertEquals(serializer.data['sub_comment'], 'And Merry Christmas!')
 
+    def test_partial_update(self):
+        msg = 'Merry New Year!'
+        partial_data = {'content': msg}
+        serializer = CommentSerializer(self.comment, data=partial_data)
+        self.assertEquals(serializer.is_valid(), False)
+        serializer = CommentSerializer(self.comment, data=partial_data, partial=True)
+        expected = self.comment
+        self.assertEqual(serializer.is_valid(), True)
+        self.assertEquals(serializer.object, expected)
+        self.assertTrue(serializer.object is expected)
+        self.assertEquals(serializer.data['content'], msg)
+
     def test_model_fields_as_expected(self):
         """
         Make sure that the fields returned are the same as defined