__all__ doesn't work on second query

[mjschultz]

It seems like this test case should pass:

diff --git a/tests/test_backends.py b/tests/test_backends.py
index 1394e3a..88fb8d3 100644
--- a/tests/test_backends.py
+++ b/tests/test_backends.py
@@ -16,3 +16,14 @@ class BackendTest(APITestCase):

         self.assertEqual(len(response.data), 1)
         self.assertEqual(response.data[0]['username'], 'user1')
+
+    def test_django_filter_compatibility_twice(self):
+        response = self.client.get('/dffield-users/', {'username': 'user1'}, content_type='json')
+
+        self.assertEqual(len(response.data), 1)
+        self.assertEqual(response.data[0]['username'], 'user1')
+
+        response = self.client.get('/dffield-users/', {'username': 'user1'}, content_type='json')
+
+        self.assertEqual(len(response.data), 1)
+        self.assertEqual(response.data[0]['username'], 'user1')
diff --git a/tests/testapp/urls.py b/tests/testapp/urls.py
index 23e87ba..5f7b405 100644
--- a/tests/testapp/urls.py
+++ b/tests/testapp/urls.py
@@ -7,6 +7,7 @@ from . import views

 router = routers.DefaultRouter()
 router.register(r'df-users', views.DFUserViewSet, base_name='df-users')
+router.register(r'dffield-users', views.DFFieldUserViewSet, base_name='dffield-users')
 router.register(r'users', views.UserViewSet,)
 router.register(r'notes', views.NoteViewSet,)

diff --git a/tests/testapp/views.py b/tests/testapp/views.py
index 7e3956f..75761a0 100644
--- a/tests/testapp/views.py
+++ b/tests/testapp/views.py
@@ -16,6 +16,17 @@ class DFUserViewSet(viewsets.ModelViewSet):
     filter_class = DFUserFilter


+class DFFieldUserViewSet(viewsets.ModelViewSet):
+    # used to test compatibility with the drf-filters backend
+    # with standard django-filter FilterSets.
+    queryset = User.objects.all()
+    serializer_class = UserSerializer
+    filter_backends = (backends.DjangoFilterBackend, )
+    filter_fields = {
+        'username': '__all__'
+    }
+
+
 class UserViewSet(viewsets.ModelViewSet):
     queryset = User.objects.all()
     serializer_class = UserSerializer

But it fails on the second get. It looks like the generation of fields runs through and deletes the Meta.fields which is a reference to the underlying filter_fields which are then deleted.

On the second API call, the get_filter_class will return None because there are no filter_fields or filter_class causing no filtering to be applied.

[rpkilby]

Oh, good catch. This should work if you use a custom filter_class instead of filter_fields. I'll try to get around to fixing this over the weekend.

As to the problem, it shouldn't be deleting Meta.fields, it's deleting the field with the '__all__' lookups shortcut and placing an AllLookupsFilter directly on the FilterSet. The problem is that the FilterSet is regenerated on every call, so with the deleted lookup, the filter can't be regenerated.

[rpkilby]

This should now be fixed on master. Thanks for providing a test case!