Guard against erronous direct .queryset evaluation in CBVs.

rest_framework/views.py

@@ -7,6 +7,7 @@ import inspect
 import warnings
 
 from django.core.exceptions import PermissionDenied
+from django.db import models
 from django.http import Http404
 from django.utils import six
 from django.utils.encoding import smart_text
@@ -118,8 +119,19 @@ class APIView(View):
         This allows us to discover information about the view when we do URL
         reverse lookups.  Used for breadcrumb generation.
         """
+        if isinstance(getattr(cls, 'queryset', None), models.QuerySet):
+            def force_evaluation():
+                raise AssertionError(
+                    'Do not evaluate the `.queryset` attribute directly, '
+                    'as the result will be cached and reused between requests. '
+                    'Use `.all()` or call `.get_queryset()` instead.'
+                )
+
+            cls.queryset._fetch_all = force_evaluation
+
         view = super(APIView, cls).as_view(**initkwargs)
         view.cls = cls
+
         # Note: session based authentication is explicitly CSRF validated,
         # all other authentication is CSRF exempt.
         return csrf_exempt(view)

tests/test_generics.py

@@ -1,12 +1,14 @@
 from __future__ import unicode_literals
 
 import django
+import pytest
 from django.db import models
 from django.shortcuts import get_object_or_404
 from django.test import TestCase
 from django.utils import six
 
 from rest_framework import generics, renderers, serializers, status
+from rest_framework.response import Response
 from rest_framework.test import APIRequestFactory
 from tests.models import (
     BasicModel, ForeignKeySource, ForeignKeyTarget, RESTFrameworkModel
@@ -527,3 +529,17 @@ class TestFilterBackendAppliedToViews(TestCase):
         response = view(request).render()
         self.assertContains(response, 'field_b')
         self.assertNotContains(response, 'field_a')
+
+
+class TestGuardedQueryset(TestCase):
+    def test_guarded_queryset(self):
+        class QuerysetAccessError(generics.ListAPIView):
+            queryset = BasicModel.objects.all()
+
+            def get(self, request):
+                return Response(list(self.queryset))
+
+        view = QuerysetAccessError.as_view()
+        request = factory.get('/')
+        with pytest.raises(AssertionError):
+            view(request).render()