From df1fc8df7d27ea3caee0ce3474a2fb5549ba9b45 Mon Sep 17 00:00:00 2001
From: Benjamin Mampaey <benjamin.mampaey@oma.be>
Date: Thu, 25 Feb 2016 12:11:22 +0100
Subject: [PATCH] Fixed issue 3957 where serializer_class wass accessed
 directly on the view in OrderingFilter backend instead of calling the view's
 get_serializer_class method

---
 rest_framework/filters.py |  5 ++--
 tests/test_filters.py     | 48 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/rest_framework/filters.py b/rest_framework/filters.py
index 42e77d910..8d287b1ce 100644
--- a/rest_framework/filters.py
+++ b/rest_framework/filters.py
@@ -227,8 +227,9 @@ class OrderingFilter(BaseFilterBackend):
 
         if valid_fields is None:
             # Default to allowing filtering on serializer fields
-            serializer_class = getattr(view, 'serializer_class')
-            if serializer_class is None:
+            try:
+                serializer_class = view.get_serializer_class()
+            except AssertionError:
                 msg = ("Cannot use %s on a view which does not have either a "
                        "'serializer_class' or 'ordering_fields' attribute.")
                 raise ImproperlyConfigured(msg % self.__class__.__name__)
diff --git a/tests/test_filters.py b/tests/test_filters.py
index 729a7b75b..9809c9bfe 100644
--- a/tests/test_filters.py
+++ b/tests/test_filters.py
@@ -5,6 +5,7 @@ import unittest
 from decimal import Decimal
 
 from django.conf.urls import url
+from django.core.exceptions import ImproperlyConfigured
 from django.core.urlresolvers import reverse
 from django.db import models
 from django.test import TestCase
@@ -585,6 +586,53 @@ class OrderingFilterTests(TestCase):
             )
             OrderingFilterModel(title=title, text=text).save()
 
+    def test_get_valid_fields_from_explicit_serializer_class(self):
+        class OrderingListView(generics.ListAPIView):
+            queryset = OrderingFilterModel.objects.all()
+            serializer_class = OrderingFilterSerializer
+            filter_backends = (filters.OrderingFilter, )
+            ordering_fields = None
+
+        queryset = OrderingFilterModel.objects.all()
+        view = OrderingListView()
+        backend = filters.OrderingFilter()
+        valid_fields = backend.get_valid_fields(queryset, view)
+        expected_valid_fields = [(field.source or field_name, field.label)
+                                 for (field_name, field) in OrderingFilterSerializer().fields.items()
+                                 if not getattr(field, 'write_only', False) and not field.source == '*']
+        self.assertEqual(valid_fields, expected_valid_fields)
+
+    def test_get_valid_fields_from_explicit_get_serializer_class(self):
+        class OrderingListView(generics.ListAPIView):
+            queryset = OrderingFilterModel.objects.all()
+            filter_backends = (filters.OrderingFilter,)
+            ordering_fields = None
+
+            def get_serializer_class(self):
+                return OrderingFilterSerializer
+
+        queryset = OrderingFilterModel.objects.all()
+        view = OrderingListView()
+        backend = filters.OrderingFilter()
+        valid_fields = backend.get_valid_fields(queryset, view)
+        expected_valid_fields = [(field.source or field_name, field.label)
+                                 for (field_name, field) in OrderingFilterSerializer().fields.items()
+                                 if not getattr(field, 'write_only', False) and not field.source == '*']
+        self.assertEqual(valid_fields, expected_valid_fields)
+
+    def test_improperly_configured_error_from_get_valid_fields(self):
+        class OrderingListView(generics.ListAPIView):
+            queryset = OrderingFilterModel.objects.all()
+            filter_backends = (filters.OrderingFilter,)
+            ordering_fields = None
+            serializer_class = None
+
+        queryset = OrderingFilterModel.objects.all()
+        view = OrderingListView()
+        backend = filters.OrderingFilter()
+        with self.assertRaises(ImproperlyConfigured):
+            backend.get_valid_fields(queryset, view)
+
     def test_ordering(self):
         class OrderingListView(generics.ListAPIView):
             queryset = OrderingFilterModel.objects.all()