Fix flush with reverse m2m changed signal

waffle/signals.py

@@ -8,4 +8,8 @@
 @receiver(m2m_changed, sender=get_waffle_flag_model().groups.through)
 def flag_membership_changed(sender, instance, action, **kwargs):
     if action in ('post_add', 'post_remove'):
-        instance.flush()
+        if kwargs['reverse']:
+            for flag in get_waffle_flag_model().objects.filter(pk__in=kwargs['pk_set']):
+                flag.flush()
+        else:
+            instance.flush()

waffle/tests/test_waffle.py

@@ -164,6 +164,29 @@ def test_user(self):
         response = process_request(request, views.flag_in_view)
         self.assertEqual(b'off', response.content)
 
+    def test_remove_from_user(self):
+        """Same operation of `test_user` but performed with reverse relation"""
+        user = get_user_model().objects.create(username='foo')
+        flag = waffle.get_waffle_flag_model().objects.create(name='myflag')
+        flag.users.add(user)
+
+        request = get()
+        request.user = user
+        response = process_request(request, views.flag_in_view)
+        self.assertEqual(b'on', response.content)
+        assert 'dwf_myflag' not in response.cookies
+
+        request.user = get_user_model().objects.create(username='someone_else')
+        response = process_request(request, views.flag_in_view)
+        self.assertEqual(b'off', response.content)
+        assert 'dwf_myflag' not in response.cookies
+
+        # Unsetting the flag on a user should have an effect.
+        user.flag_set.remove(flag)
+        request.user = user
+        response = process_request(request, views.flag_in_view)
+        self.assertEqual(b'off', response.content)
+
     def test_group(self):
         """Test the per-group switch."""
         group = Group.objects.create(name='foo')
@@ -191,6 +214,33 @@ def test_group(self):
         response = process_request(request, views.flag_in_view)
         self.assertEqual(b'off', response.content)
 
+    def test_remove_from_group(self):
+        """Same operation of `test_group` but performed with reverse relation"""
+        group = Group.objects.create(name='foo')
+        user = get_user_model().objects.create(username='bar')
+        user.groups.add(group)
+
+        flag = waffle.get_waffle_flag_model().objects.create(name='myflag')
+        flag.groups.add(group)
+
+        request = get()
+        request.user = user
+        response = process_request(request, views.flag_in_view)
+        self.assertEqual(b'on', response.content)
+        assert 'dwf_myflag' not in response.cookies
+
+        request.user = get_user_model()(username='someone_else')
+        request.user.save()
+        response = process_request(request, views.flag_in_view)
+        self.assertEqual(b'off', response.content)
+        assert 'dwf_myflag' not in response.cookies
+
+        # Unsetting the flag on a group should have an effect.
+        group.flag_set.remove(flag)
+        request.user = user
+        response = process_request(request, views.flag_in_view)
+        self.assertEqual(b'off', response.content)
+
     def test_authenticated(self):
         """Test the authenticated/anonymous switch."""
         waffle.get_waffle_flag_model().objects.create(name='myflag', authenticated=True)