Allow DjangoObjectPermissions to use views that define get_queryset

docs/api-guide/permissions.md

@@ -150,7 +150,7 @@ Similar to `DjangoModelPermissions`, but also allows unauthenticated users to ha
 
 This permission class ties into Django's standard [object permissions framework][objectpermissions] that allows per-object permissions on models.  In order to use this permission class, you'll also need to add a permission backend that supports object-level permissions, such as [django-guardian][guardian].
 
-As with `DjangoModelPermissions`, this permission must only be applied to views that have a `.queryset` property. Authorization will only be granted if the user *is authenticated* and has the *relevant per-object permissions* and *relevant model permissions* assigned.
+As with `DjangoModelPermissions`, this permission must only be applied to views that have a `.queryset` property or `.get_queryset()` method. Authorization will only be granted if the user *is authenticated* and has the *relevant per-object permissions* and *relevant model permissions* assigned.
 
 * `POST` requests require the user to have the `add` permission on the model instance.
 * `PUT` and `PATCH` requests require the user to have the `change` permission on the model instance.

rest_framework/permissions.py

@@ -3,6 +3,7 @@ Provides a set of pluggable permission policies.
 """
 from __future__ import unicode_literals
 from django.http import Http404
+from django.utils import six
 from rest_framework.compat import get_model_name
 
 SAFE_METHODS = ('GET', 'HEAD', 'OPTIONS')
@@ -109,8 +110,6 @@ class DjangoModelPermissions(BasePermission):
     def has_permission(self, request, view):
         try:
             queryset = view.get_queryset()
-        except AttributeError:
-            queryset = getattr(view, 'queryset', None)
         except AssertionError:
             # view.get_queryset() didn't find .queryset
             queryset = None
@@ -172,7 +171,14 @@ class DjangoObjectPermissions(DjangoModelPermissions):
         return [perm % kwargs for perm in self.perms_map[method]]
 
     def has_object_permission(self, request, view, obj):
-        model_cls = view.queryset.model
+        try:
+            queryset = view.get_queryset()
+        except AssertionError as exc:
+            # view.get_queryset() didn't find .queryset
+            raise six.raise_from(AssertionError(
+                'Cannot apply DjangoObjectPermissions on a view that '
+                'does not have `.queryset` property nor redefines `.get_queryset()`.'), exc)
+        model_cls = queryset.model
         user = request.user
 
         perms = self.get_required_object_permissions(request.method, model_cls)

tests/test_permissions.py

@@ -227,6 +227,18 @@ class ObjectPermissionListView(generics.ListAPIView):
 object_permissions_list_view = ObjectPermissionListView.as_view()
 
 
+class GetQuerysetObjectPermissionInstanceView(generics.RetrieveUpdateDestroyAPIView):
+    serializer_class = BasicPermSerializer
+    authentication_classes = [authentication.BasicAuthentication]
+    permission_classes = [ViewObjectPermissions]
+
+    def get_queryset(self):
+        return BasicPermModel.objects.all()
+
+
+get_queryset_object_permissions_view = GetQuerysetObjectPermissionInstanceView.as_view()
+
+
 @unittest.skipUnless(guardian, 'django-guardian not installed')
 class ObjectPermissionsIntegrationTests(TestCase):
     """
@@ -326,6 +338,15 @@ class ObjectPermissionsIntegrationTests(TestCase):
         response = object_permissions_view(request, pk='1')
         self.assertEqual(response.status_code, status.HTTP_404_NOT_FOUND)
 
+    def test_can_read_get_queryset_permissions(self):
+        """
+        same as ``test_can_read_permissions`` but with a view
+        that rely on ``.get_queryset()`` instead of ``.queryset``.
+        """
+        request = factory.get('/1', HTTP_AUTHORIZATION=self.credentials['readonly'])
+        response = get_queryset_object_permissions_view(request, pk='1')
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+
     # Read list
     def test_can_read_list_permissions(self):
         request = factory.get('/', HTTP_AUTHORIZATION=self.credentials['readonly'])