Fix for pks returning as strings when set in pre_save. Fixes #482. Thanks to @n8agrin for the bug report.

rest_framework/mixins.py

@@ -113,6 +113,10 @@ class UpdateModelMixin(object):
             slug_field = self.get_slug_field()
             setattr(obj, slug_field, slug)
 
+        # Ensure we clean the attributes so that we don't eg return integer
+        # pk using a string representation, as provided by the url conf kwarg.
+        obj.full_clean()
+
 
 class DestroyModelMixin(object):
     """

rest_framework/serializers.py

@@ -497,8 +497,8 @@ class ModelSerializer(Serializer):
         if instance is not None:
             for key, val in attrs.items():
                 setattr(instance, key, val)
-            return instance
 
+        else:
             # Reverse relations
             for (obj, model) in self.opts.model._meta.get_all_related_m2m_objects_with_model():
                 field_name = obj.field.related_query_name()
@@ -511,11 +511,13 @@ class ModelSerializer(Serializer):
                     self.m2m_data[field.name] = attrs.pop(field.name)
 
             instance = self.opts.model(**attrs)
+
         try:
             instance.full_clean(exclude=self.get_validation_exclusions())
         except ValidationError, err:
             self._errors = err.message_dict
             return None
+
         return instance
 
     def save(self, save_m2m=True):

rest_framework/tests/generics.py

@@ -175,7 +175,7 @@ class TestInstanceView(TestCase):
         content = {'text': 'foobar'}
         request = factory.put('/1', json.dumps(content),
                               content_type='application/json')
-        response = self.view(request, pk=1).render()
+        response = self.view(request, pk='1').render()
         self.assertEquals(response.status_code, status.HTTP_200_OK)
         self.assertEquals(response.data, {'id': 1, 'text': 'foobar'})
         updated = self.objects.get(id=1)