Adds 'exclude' option to data binding (#400)

channels/binding/base.py

@@ -67,6 +67,7 @@ class Binding(object):
     # if you want to really send all fields, use fields = ['__all__']
 
     fields = None
+    exclude = None
 
     # Decorators
     channel_session_user = True
@@ -95,9 +96,9 @@ class Binding(object):
                 return []
             else:
                 raise ValueError("You must set the model attribute on Binding %r!" % cls)
-        # If fields is not defined, raise an error
+        # If neither fields nor exclude are not defined, raise an error
-        if cls.fields is None:
+        if cls.fields is None and cls.exclude is None:
-            raise ValueError("You must set the fields attribute on Binding %r!" % cls)
+            raise ValueError("You must set the fields or exclude attribute on Binding %r!" % cls)
         # Optionally resolve model strings
         if isinstance(cls.model, six.string_types):
             cls.model = apps.get_model(cls.model)

channels/binding/websockets.py

@@ -55,10 +55,13 @@ class WebsocketBinding(Binding):
         """
         Serializes model data into JSON-compatible types.
         """
-        if list(self.fields) == ['__all__']:
+        if self.fields is not None:
-            fields = None
+            if list(self.fields) == ['__all__']:
+                fields = None
+            else:
+                fields = self.fields
         else:
-            fields = self.fields
+            fields = [f.name for f in instance._meta.get_fields() if f.name not in self.exclude]
         data = serializers.serialize('json', [instance], fields=fields)
         return json.loads(data)[0]['fields']
 
@@ -109,9 +112,15 @@ class WebsocketBinding(Binding):
     def update(self, pk, data):
         instance = self.model.objects.get(pk=pk)
         hydrated = self._hydrate(pk, data)
-        for name in data.keys():
+
-            if name in self.fields or self.fields == ['__all__']:
+        if self.fields is not None:
-                setattr(instance, name, getattr(hydrated.object, name))
+            for name in data.keys():
+                if name in self.fields or self.fields == ['__all__']:
+                    setattr(instance, name, getattr(hydrated.object, name))
+        else:
+            for name in data.keys():
+                if name not in self.exclude:
+                    setattr(instance, name, getattr(hydrated.object, name))
         instance.save()
 
 

channels/tests/test_binding.py

@@ -58,6 +58,65 @@ class TestsBinding(ChannelTestCase):
             received = client.receive()
             self.assertIsNone(received)
 
+    def test_trigger_outbound_create_exclude(self):
+        class TestBinding(WebsocketBinding):
+            model = User
+            stream = 'test'
+            exclude = ['first_name', 'last_name']
+
+            @classmethod
+            def group_names(cls, instance, action):
+                return ["users_exclude"]
+
+            def has_permission(self, user, action, pk):
+                return True
+
+        with apply_routes([route('test', TestBinding.consumer)]):
+            client = HttpClient()
+            client.join_group('users_exclude')
+
+            user = User.objects.create(username='test', email='test@test.com')
+            consumer_finished.send(sender=None)
+            consumer_finished.send(sender=None)
+            received = client.receive()
+
+            self.assertTrue('payload' in received)
+            self.assertTrue('action' in received['payload'])
+            self.assertTrue('data' in received['payload'])
+            self.assertTrue('username' in received['payload']['data'])
+            self.assertTrue('email' in received['payload']['data'])
+            self.assertTrue('password' in received['payload']['data'])
+            self.assertTrue('model' in received['payload'])
+            self.assertTrue('pk' in received['payload'])
+
+            self.assertFalse('last_name' in received['payload']['data'])
+            self.assertFalse('first_name' in received['payload']['data'])
+
+            self.assertEqual(received['payload']['action'], 'create')
+            self.assertEqual(received['payload']['model'], 'auth.user')
+            self.assertEqual(received['payload']['pk'], user.pk)
+
+            self.assertEqual(received['payload']['data']['email'], 'test@test.com')
+            self.assertEqual(received['payload']['data']['username'], 'test')
+            self.assertEqual(received['payload']['data']['password'], '')
+
+            received = client.receive()
+            self.assertIsNone(received)
+
+    def test_omit_fields_and_exclude(self):
+        def _declare_class():
+            class TestBinding(WebsocketBinding):
+                model = User
+                stream = 'test'
+
+                @classmethod
+                def group_names(cls, instance, action):
+                    return ["users_omit"]
+
+                def has_permission(self, user, action, pk):
+                    return True
+        self.assertRaises(ValueError, _declare_class)
+
     def test_trigger_outbound_update(self):
         class TestBinding(WebsocketBinding):
             model = User

docs/binding.rst

@@ -81,7 +81,8 @@ always provide:
 
 * ``fields`` is a whitelist of fields to return in the serialized request.
   Channels does not default to all fields for security concerns; if you want
-  this, set it to the value ``["__all__"]``.
+  this, set it to the value ``["__all__"]``. As an alternative, ``exclude``
+  acts as a blacklist of fields.
 
 * ``group_names`` returns a list of groups to send outbound updates to based
   on the model and action. For example, you could dispatch posts on different