Add forgotten status to Room Details API (#13503)

6 files changed, 101 insertions, 1 deletions

diff --git a/changelog.d/13503.feature b/changelog.d/13503.feature
new file mode 100644
index 0000000000..4baabd1e32
--- /dev/null
+++ b/changelog.d/13503.feature
@@ -0,0 +1 @@
+Add forgotten status to Room Details API.
\ No newline at end of file
diff --git a/docs/admin_api/rooms.md b/docs/admin_api/rooms.md
index 9aa489e4a3..ac7c54c20e 100644
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -302,6 +302,8 @@ The following fields are possible in the JSON response body:
 * `state_events` - Total number of state_events of a room. Complexity of the room.
 * `room_type` - The type of the room taken from the room's creation event; for example "m.space" if the room is a space.
   If the room does not define a type, the value will be `null`.
+* `forgotten` - Whether all local users have
+  [forgotten](https://spec.matrix.org/latest/client-server-api/#leaving-rooms) the room.
 
 The API is:
 
@@ -330,7 +332,8 @@ A response body like the following is returned:
   "guest_access": null,
   "history_visibility": "shared",
   "state_events": 93534,
-  "room_type": "m.space"
+  "room_type": "m.space",
+  "forgotten": false
 }
 ```
 
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index 9d953d58de..68054ffc28 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -303,6 +303,7 @@ class RoomRestServlet(RestServlet):
 
         members = await self.store.get_users_in_room(room_id)
         ret["joined_local_devices"] = await self.store.count_devices_by_users(members)
+        ret["forgotten"] = await self.store.is_locally_forgotten_room(room_id)
 
         return HTTPStatus.OK, ret
 
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 5e5f607a14..827c1f1efd 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -1215,6 +1215,30 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             "get_forgotten_rooms_for_user", _get_forgotten_rooms_for_user_txn
         )
 
+    async def is_locally_forgotten_room(self, room_id: str) -> bool:
+        """Returns whether all local users have forgotten this room_id.
+
+        Args:
+            room_id: The room ID to query.
+
+        Returns:
+            Whether the room is forgotten.
+        """
+
+        sql = """
+            SELECT count(*) > 0 FROM local_current_membership
+            INNER JOIN room_memberships USING (room_id, event_id)
+            WHERE
+                room_id = ?
+                AND forgotten = 0;
+        """
+
+        rows = await self.db_pool.execute("is_forgotten_room", None, sql, room_id)
+
+        # `count(*)` returns always an integer
+        # If any rows still exist it means someone has not forgotten this room yet
+        return not rows[0][0]
+
     async def get_rooms_user_has_been_in(self, user_id: str) -> Set[str]:
         """Get all rooms that the user has ever been in.
 
diff --git a/tests/rest/admin/test_room.py b/tests/rest/admin/test_room.py
index dd5000679a..fd6da557c1 100644
--- a/tests/rest/admin/test_room.py
+++ b/tests/rest/admin/test_room.py
@@ -1633,6 +1633,7 @@ class RoomTestCase(unittest.HomeserverTestCase):
         self.assertIn("history_visibility", channel.json_body)
         self.assertIn("state_events", channel.json_body)
         self.assertIn("room_type", channel.json_body)
+        self.assertIn("forgotten", channel.json_body)
         self.assertEqual(room_id_1, channel.json_body["room_id"])
 
     def test_single_room_devices(self) -> None:
diff --git a/tests/storage/test_roommember.py b/tests/storage/test_roommember.py
index 240b02cb9f..ceec690285 100644
--- a/tests/storage/test_roommember.py
+++ b/tests/storage/test_roommember.py
@@ -23,6 +23,7 @@ from synapse.util import Clock
 
 from tests import unittest
 from tests.server import TestHomeServer
+from tests.test_utils import event_injection
 
 
 class RoomMemberStoreTestCase(unittest.HomeserverTestCase):
@@ -157,6 +158,75 @@ class RoomMemberStoreTestCase(unittest.HomeserverTestCase):
         # Check that alice's display name is now None
         self.assertEqual(row[0]["display_name"], None)
 
+    def test_room_is_locally_forgotten(self):
+        """Test that when the last local user has forgotten a room it is known as forgotten."""
+        # join two local and one remote user
+        self.room = self.helper.create_room_as(self.u_alice, tok=self.t_alice)
+        self.get_success(
+            event_injection.inject_member_event(self.hs, self.room, self.u_bob, "join")
+        )
+        self.get_success(
+            event_injection.inject_member_event(
+                self.hs, self.room, self.u_charlie.to_string(), "join"
+            )
+        )
+        self.assertFalse(
+            self.get_success(self.store.is_locally_forgotten_room(self.room))
+        )
+
+        # local users leave the room and the room is not forgotten
+        self.get_success(
+            event_injection.inject_member_event(
+                self.hs, self.room, self.u_alice, "leave"
+            )
+        )
+        self.get_success(
+            event_injection.inject_member_event(self.hs, self.room, self.u_bob, "leave")
+        )
+        self.assertFalse(
+            self.get_success(self.store.is_locally_forgotten_room(self.room))
+        )
+
+        # first user forgets the room, room is not forgotten
+        self.get_success(self.store.forget(self.u_alice, self.room))
+        self.assertFalse(
+            self.get_success(self.store.is_locally_forgotten_room(self.room))
+        )
+
+        # second (last local) user forgets the room and the room is forgotten
+        self.get_success(self.store.forget(self.u_bob, self.room))
+        self.assertTrue(
+            self.get_success(self.store.is_locally_forgotten_room(self.room))
+        )
+
+    def test_join_locally_forgotten_room(self):
+        """Tests if a user joins a forgotten room the room is not forgotten anymore."""
+        self.room = self.helper.create_room_as(self.u_alice, tok=self.t_alice)
+        self.assertFalse(
+            self.get_success(self.store.is_locally_forgotten_room(self.room))
+        )
+
+        # after leaving and forget the room, it is forgotten
+        self.get_success(
+            event_injection.inject_member_event(
+                self.hs, self.room, self.u_alice, "leave"
+            )
+        )
+        self.get_success(self.store.forget(self.u_alice, self.room))
+        self.assertTrue(
+            self.get_success(self.store.is_locally_forgotten_room(self.room))
+        )
+
+        # after rejoin the room is not forgotten anymore
+        self.get_success(
+            event_injection.inject_member_event(
+                self.hs, self.room, self.u_alice, "join"
+            )
+        )
+        self.assertFalse(
+            self.get_success(self.store.is_locally_forgotten_room(self.room))
+        )
+
 
 class CurrentStateMembershipUpdateTestCase(unittest.HomeserverTestCase):
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None: