switch to a dedicated filter for read list object permissions

rest_framework/filters.py

@@ -4,7 +4,7 @@ returned by list views.
 """
 from __future__ import unicode_literals
 from django.db import models
-from rest_framework.compat import django_filters, six
+from rest_framework.compat import django_filters, six, guardian
 from functools import reduce
 import operator
 
@@ -23,6 +23,22 @@ class BaseFilterBackend(object):
         raise NotImplementedError(".filter_queryset() must be overridden.")
 
 
+class ObjectPermissionReaderFilter(BaseFilterBackend):
+    """
+    A filter backend that limits results to those where the requesting user
+    has read object level permissions.
+    """
+    def __init__(self):
+        assert guardian, 'Using ObjectPermissionReaderFilter, but django-guardian is not installed'
+
+    def filter_queryset(self, request, queryset, view):
+        user = request.user
+        model_cls = queryset.model
+        model_name = model_cls._meta.module_name
+        permission = 'read_' + model_name
+        return guardian.shortcuts.get_objects_for_user(user, permission, queryset)
+
+
 class DjangoFilterBackend(BaseFilterBackend):
     """
     A filter backend that uses django-filter.

rest_framework/permissions.py

@@ -9,6 +9,7 @@ SAFE_METHODS = ['GET', 'HEAD', 'OPTIONS']
 
 from django.http import Http404
 from rest_framework.compat import oauth2_provider_scope, oauth2_constants, guardian
+from rest_framework.filters import ObjectPermissionReaderFilter
 
 
 class BasePermission(object):
@@ -169,7 +170,7 @@ class DjangoObjectLevelModelPermissions(DjangoModelPermissions):
         'destroy': 'delete',
     }
 
-    def _get_names(self, view):
+    def _get_model_name(self, view):
         model_cls = getattr(view, 'model', None)
         queryset = getattr(view, 'queryset', None)
 
@@ -182,19 +183,17 @@ class DjangoObjectLevelModelPermissions(DjangoModelPermissions):
 
     def has_permission(self, request, view):
         if view.action == 'list':
-            user = request.user
             queryset = view.get_queryset()
-            model_name = self._get_names(view)
-            view.queryset = guardian.shortcuts.get_objects_for_user(user, 'read_' + model_name, queryset)  #TODO: move to filter
+            view.queryset = ObjectPermissionReaderFilter().filter_queryset(request, queryset, view)
         return super(DjangoObjectLevelModelPermissions, self).has_permission(request, view)
 
     def has_object_permission(self, request, view, obj):
-        user = request.user
-        model_name = self._get_names(view)
         action = self.action_perm_map.get(view.action)
-
         assert action, "Tried to determine object permissions but no action specified in view"
 
+        user = request.user
+        model_name = self._get_model_name(view)
+
         perm = "{action}_{model_name}".format(action=action, model_name=model_name)
         check = user.has_perm(perm, obj)
         if not check: