Fix bug in device list caching when remote users leave rooms (#13749)

When a remote user leaves the last room shared with the homeserver, we
have to mark their device list as unsubscribed, otherwise we would hold
on to a stale device list in our cache. Crucially, the device list would
remain cached even after the remote user rejoined the room, which could
lead to E2EE failures until the next change to the remote user's device
list.

Fixes #13651.

Signed-off-by: Sean Quah <seanq@matrix.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/tests/handlers/test_e2e_keys.py b/tests/handlers/test_e2e_keys.py
index 1e6ad4b663..95698bc275 100644
--- a/tests/handlers/test_e2e_keys.py
+++ b/tests/handlers/test_e2e_keys.py
@@ -891,6 +891,12 @@ class E2eKeysHandlerTestCase(unittest.HomeserverTestCase):
             new_callable=mock.MagicMock,
             return_value=make_awaitable(["some_room_id"]),
         )
+        mock_get_users = mock.patch.object(
+            self.store,
+            "get_users_server_still_shares_room_with",
+            new_callable=mock.MagicMock,
+            return_value=make_awaitable({remote_user_id}),
+        )
         mock_request = mock.patch.object(
             self.hs.get_federation_client(),
             "query_user_devices",
@@ -898,7 +904,7 @@ class E2eKeysHandlerTestCase(unittest.HomeserverTestCase):
             return_value=make_awaitable(response_body),
         )
 
-        with mock_get_rooms, mock_request as mocked_federation_request:
+        with mock_get_rooms, mock_get_users, mock_request as mocked_federation_request:
             # Make the first query and sanity check it succeeds.
             response_1 = self.get_success(
                 e2e_handler.query_devices(