RLS: Remove forgotten room from skiplist (#29933)

* Dispatch an action when room is forgotten

* Dispatch an action when room is forgotten

* Remove room on action

* Add test

* Write test for matrixchat

* Add payload info to comment

src/components/structures/MatrixChat.tsx

@@ -107,6 +107,7 @@ import Views from "../../Views";
 import { type FocusNextType, type ViewRoomPayload } from "../../dispatcher/payloads/ViewRoomPayload";
 import { type ViewHomePagePayload } from "../../dispatcher/payloads/ViewHomePagePayload";
 import { type AfterLeaveRoomPayload } from "../../dispatcher/payloads/AfterLeaveRoomPayload";
+import { type AfterForgetRoomPayload } from "../../dispatcher/payloads/AfterForgetRoomPayload";
 import { type DoAfterSyncPreparedPayload } from "../../dispatcher/payloads/DoAfterSyncPreparedPayload";
 import { type ViewStartChatOrReusePayload } from "../../dispatcher/payloads/ViewStartChatOrReusePayload";
 import { leaveRoomBehaviour } from "../../utils/leave-behaviour";
@@ -1269,10 +1270,12 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
                     dis.dispatch({ action: Action.ViewHomePage });
                 }
 
-                // We have to manually update the room list because the forgotten room will not
-                // be notified to us, therefore the room list will have no other way of knowing
-                // the room is forgotten.
-                if (room) RoomListStore.instance.manualRoomUpdate(room, RoomUpdateCause.RoomRemoved);
+                if (room) {
+                    // Legacy room list store needs to be told to manually remove this room
+                    RoomListStore.instance.manualRoomUpdate(room, RoomUpdateCause.RoomRemoved);
+                    // New room list store will remove the room on the following dispatch
+                    dis.dispatch<AfterForgetRoomPayload>({ action: Action.AfterForgetRoom, room });
+                }
             })
             .catch((err) => {
                 const errCode = err.errcode || _td("error|unknown_error_code");

src/dispatcher/actions.ts

@@ -235,6 +235,12 @@ export enum Action {
      */
     AfterLeaveRoom = "after_leave_room",
 
+    /**
+     * Dispatched after a room has been successfully forgotten
+     * Should be used with AfterForgetRoomPayload.
+     */
+    AfterForgetRoom = "after_forget_room",
+
     /**
      * Used to defer actions until after sync is complete
      * LifecycleStore will emit deferredAction payload after 'MatrixActions.sync'

src/dispatcher/payloads/AfterForgetRoomPayload.ts

@@ -0,0 +1,16 @@
+/*
+ * Copyright 2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+import { type Room } from "matrix-js-sdk/src/matrix";
+
+import { type Action } from "../actions";
+import { type ActionPayload } from "../payloads";
+
+export interface AfterForgetRoomPayload extends ActionPayload {
+    action: Action.AfterForgetRoom;
+    room: Room;
+}

src/stores/room-list-v3/RoomListStoreV3.ts

@@ -34,6 +34,7 @@ import { type Sorter, SortingAlgorithm } from "./skip-list/sorters";
 import { SettingLevel } from "../../settings/SettingLevel";
 import { MARKED_UNREAD_TYPE_STABLE, MARKED_UNREAD_TYPE_UNSTABLE } from "../../utils/notifications";
 import { getChangedOverrideRoomMutePushRules } from "../room-list/utils/roomMute";
+import { Action } from "../../dispatcher/actions";
 
 /**
  * These are the filters passed to the room skip list.
@@ -245,6 +246,13 @@ export class RoomListStoreV3Class extends AsyncStoreWithClient<EmptyObject> {
                 this.addRoomAndEmit(payload.room, true);
                 break;
             }
+
+            case Action.AfterForgetRoom: {
+                const room = payload.room;
+                this.roomSkipList.removeRoom(room);
+                this.emit(LISTS_UPDATE_EVENT);
+                break;
+            }
         }
     }