From b7cd28bd2983d50ab140084a196f4d1ad9dcd928 Mon Sep 17 00:00:00 2001
From: Andy Balaam <andy.balaam@matrix.org>
Date: Fri, 3 Feb 2023 09:14:44 +0000
Subject: [PATCH] Support MSC3946 in RoomListStore (#10054)

---
 src/stores/room-list/RoomListStore.ts       |  8 +--
 test/stores/room-list/RoomListStore-test.ts | 56 +++++++++++++++++++--
 2 files changed, 56 insertions(+), 8 deletions(-)

diff --git a/src/stores/room-list/RoomListStore.ts b/src/stores/room-list/RoomListStore.ts
index 39d66aa9bf..09d9cca2e4 100644
--- a/src/stores/room-list/RoomListStore.ts
+++ b/src/stores/room-list/RoomListStore.ts
@@ -286,9 +286,9 @@ export class RoomListStoreClass extends AsyncStoreWithClient<IState> implements
             // If we're joining an upgraded room, we'll want to make sure we don't proliferate
             // the dead room in the list.
             const roomState: RoomState = membershipPayload.room.currentState;
-            const createEvent = roomState.getStateEvents(EventType.RoomCreate, "");
-            if (createEvent && createEvent.getContent()["predecessor"]) {
-                const prevRoom = this.matrixClient.getRoom(createEvent.getContent()["predecessor"]["room_id"]);
+            const predecessor = roomState.findPredecessor(SettingsStore.getValue("feature_dynamic_room_predecessors"));
+            if (predecessor) {
+                const prevRoom = this.matrixClient.getRoom(predecessor.roomId);
                 if (prevRoom) {
                     const isSticky = this.algorithm.stickyRoom === prevRoom;
                     if (isSticky) {
@@ -298,6 +298,8 @@ export class RoomListStoreClass extends AsyncStoreWithClient<IState> implements
                     // Note: we hit the algorithm instead of our handleRoomUpdate() function to
                     // avoid redundant updates.
                     this.algorithm.handleRoomUpdate(prevRoom, RoomUpdateCause.RoomRemoved);
+                } else {
+                    logger.warn(`Unable to find predecessor room with id ${predecessor.roomId}`);
                 }
             }
 
diff --git a/test/stores/room-list/RoomListStore-test.ts b/test/stores/room-list/RoomListStore-test.ts
index 7ceb6393a2..8ce3dff22a 100644
--- a/test/stores/room-list/RoomListStore-test.ts
+++ b/test/stores/room-list/RoomListStore-test.ts
@@ -17,6 +17,7 @@ limitations under the License.
 import { EventType, MatrixEvent, Room } from "matrix-js-sdk/src/matrix";
 
 import { MatrixDispatcher } from "../../../src/dispatcher/dispatcher";
+import SettingsStore from "../../../src/settings/SettingsStore";
 import { ListAlgorithm, SortAlgorithm } from "../../../src/stores/room-list/algorithms/models";
 import { OrderedDefaultTagIDs, RoomUpdateCause } from "../../../src/stores/room-list/models";
 import RoomListStore, { RoomListStoreClass } from "../../../src/stores/room-list/RoomListStore";
@@ -24,14 +25,14 @@ import { stubClient, upsertRoomStateEvents } from "../../test-utils";
 
 describe("RoomListStore", () => {
     const client = stubClient();
-    const roomWithCreatePredecessorId = "!roomid:example.com";
+    const newRoomId = "!roomid:example.com";
     const roomNoPredecessorId = "!roomnopreid:example.com";
     const oldRoomId = "!oldroomid:example.com";
     const userId = "@user:example.com";
     const createWithPredecessor = new MatrixEvent({
         type: EventType.RoomCreate,
         sender: userId,
-        room_id: roomWithCreatePredecessorId,
+        room_id: newRoomId,
         content: {
             predecessor: { room_id: oldRoomId, event_id: "tombstone_event_id" },
         },
@@ -41,19 +42,32 @@ describe("RoomListStore", () => {
     const createNoPredecessor = new MatrixEvent({
         type: EventType.RoomCreate,
         sender: userId,
-        room_id: roomWithCreatePredecessorId,
+        room_id: newRoomId,
         content: {},
         event_id: "$create",
         state_key: "",
     });
-    const roomWithCreatePredecessor = new Room(roomWithCreatePredecessorId, client, userId, {});
+    const predecessor = new MatrixEvent({
+        type: EventType.RoomPredecessor,
+        sender: userId,
+        room_id: newRoomId,
+        content: {
+            predecessor_room_id: oldRoomId,
+            last_known_event_id: "tombstone_event_id",
+        },
+        event_id: "$pred",
+        state_key: "",
+    });
+    const roomWithPredecessorEvent = new Room(newRoomId, client, userId, {});
+    upsertRoomStateEvents(roomWithPredecessorEvent, [predecessor]);
+    const roomWithCreatePredecessor = new Room(newRoomId, client, userId, {});
     upsertRoomStateEvents(roomWithCreatePredecessor, [createWithPredecessor]);
     const roomNoPredecessor = new Room(roomNoPredecessorId, client, userId, {});
     upsertRoomStateEvents(roomNoPredecessor, [createNoPredecessor]);
     const oldRoom = new Room(oldRoomId, client, userId, {});
     client.getRoom = jest.fn().mockImplementation((roomId) => {
         switch (roomId) {
-            case roomWithCreatePredecessorId:
+            case newRoomId:
                 return roomWithCreatePredecessor;
             case oldRoomId:
                 return oldRoom;
@@ -123,4 +137,36 @@ describe("RoomListStore", () => {
         // And no other updates happen
         expect(handleRoomUpdate).toHaveBeenCalledTimes(1);
     });
+
+    describe("When feature_dynamic_room_predecessors = true", () => {
+        beforeEach(() => {
+            jest.spyOn(SettingsStore, "getValue").mockImplementation(
+                (settingName) => settingName === "feature_dynamic_room_predecessors",
+            );
+        });
+
+        afterEach(() => {
+            jest.spyOn(SettingsStore, "getValue").mockReset();
+        });
+
+        it("Removes old room if it finds a predecessor in the m.predecessor event", () => {
+            // Given a store we can spy on
+            const { store, handleRoomUpdate } = createStore();
+
+            // When we tell it we joined a new room that has an old room as
+            // predecessor in the create event
+            const payload = {
+                oldMembership: "invite",
+                membership: "join",
+                room: roomWithPredecessorEvent,
+            };
+            store.onDispatchMyMembership(payload);
+
+            // Then the old room is removed
+            expect(handleRoomUpdate).toHaveBeenCalledWith(oldRoom, RoomUpdateCause.RoomRemoved);
+
+            // And the new room is added
+            expect(handleRoomUpdate).toHaveBeenCalledWith(roomWithPredecessorEvent, RoomUpdateCause.NewRoom);
+        });
+    });
 });