MSC3866: Apply missed filter on /users response (#20152)

For the Admin API /users endpoint, the response is meant to exclude the
approval flag when MSC3866 is enabled, but the filter that applies the
exclusion never actually got used. Fix things so that it does.

changelog.d/20152.bugfix

@@ -0,0 +1 @@
+When not using MSC3866, omit the approval flag from the response of `GET /_synapse/admin/v2/users`.

synapse/rest/admin/users.py

@@ -49,6 +49,7 @@ from synapse.rest.admin._base import (
     assert_user_is_admin,
 )
 from synapse.rest.client._base import client_patterns
+from synapse.storage.databases.main import UserPaginateResponse
 from synapse.storage.databases.main.registration import ExternalIDReuseException
 from synapse.storage.databases.main.stats import UserSortOrder
 from synapse.types import JsonDict, JsonMapping, TaskStatus, UserID
@@ -181,13 +182,16 @@ class UsersRestServletV2(RestServlet):
         )
 
         # If support for MSC3866 is not enabled, don't show the approval flag.
-        filter = None
+        users_filter = None
         if not self._msc3866_enabled:
+            users_filter = attr.filters.exclude(
+                attr.fields(UserPaginateResponse).approved
+            )
 
-            def _filter(a: attr.Attribute) -> bool:
-                return a.name != "approved"
-
-        ret = {"users": [attr.asdict(u, filter=filter) for u in users], "total": total}
+        ret = {
+            "users": [attr.asdict(u, filter=users_filter) for u in users],
+            "total": total,
+        }
         if (start + limit) < total:
             ret["next_token"] = str(start + len(users))
 

tests/rest/admin/test_user.py

@@ -1424,6 +1424,10 @@ class UsersListTestCase(unittest.HomeserverTestCase):
             self.assertIn("avatar_url", u)
             self.assertIn("creation_ts", u)
             self.assertIn("last_seen_ts", u)
+            if self.hs.config.experimental.msc3866.enabled:
+                self.assertIn("approved", u)
+            else:
+                self.assertNotIn("approved", u)
 
     def _create_users(self, number_users: int) -> None:
         """