Extra insurance that we don't mix events in the wrong timelines

Split out from #2521

spec/unit/event-timeline-set.spec.ts

@@ -55,6 +55,23 @@ describe('EventTimelineSet', () => {
  });
  };
 
+ const mkThreadResponse = (root: MatrixEvent) => utils.mkEvent({
+ event: true,
+ type: EventType.RoomMessage,
+ user: userA,
+ room: roomId,
+ content: {
+ "body": "Thread response :: " + Math.random(),
+ "m.relates_to": {
+ "event_id": root.getId(),
+ "m.in_reply_to": {
+ "event_id": root.getId()!,
+ },
+ "rel_type": "m.thread",
+ },
+ },
+ }, room.client);
+
  beforeEach(() => {
  client = utils.mock(MatrixClient, 'MatrixClient');
  client.reEmitter = utils.mock(ReEmitter, 'ReEmitter');
@@ -117,6 +134,13 @@ describe('EventTimelineSet', () => {
  });
 
  describe('addEventToTimeline', () => {
+ let thread: Thread;
+
+ beforeEach(() => {
+ (client.supportsExperimentalThreads as jest.Mock).mockReturnValue(true);
+ thread = new Thread("!thread_id:server", messageEvent, { room, client });
+ });
+
  it("Adds event to timeline", () => {
  const liveTimeline = eventTimelineSet.getLiveTimeline();
  expect(liveTimeline.getEvents().length).toStrictEqual(0);
@@ -144,6 +168,41 @@ describe('EventTimelineSet', () => {
  );
  }).not.toThrow();
  });
+
+ it("should not add an event to a timeline that does not belong to the timelineSet", () => {
+ const eventTimelineSet2 = new EventTimelineSet(room);
+ const liveTimeline2 = eventTimelineSet2.getLiveTimeline();
+ expect(liveTimeline2.getEvents().length).toStrictEqual(0);
+
+ expect(() => {
+ eventTimelineSet.addEventToTimeline(messageEvent, liveTimeline2, {
+ toStartOfTimeline: true,
+ });
+ }).toThrowError();
+ });
+
+ it("should not add a threaded reply to the main room timeline", () => {
+ const liveTimeline = eventTimelineSet.getLiveTimeline();
+ expect(liveTimeline.getEvents().length).toStrictEqual(0);
+
+ const threadedReplyEvent = mkThreadResponse(messageEvent);
+
+ eventTimelineSet.addEventToTimeline(threadedReplyEvent, liveTimeline, {
+ toStartOfTimeline: true,
+ });
+ expect(liveTimeline.getEvents().length).toStrictEqual(0);
+ });
+
+ it("should not add a normal message to the timelineSet representing a thread", () => {
+ const eventTimelineSetForThread = new EventTimelineSet(room, {}, client, thread);
+ const liveTimeline = eventTimelineSetForThread.getLiveTimeline();
+ expect(liveTimeline.getEvents().length).toStrictEqual(0);
+
+ eventTimelineSetForThread.addEventToTimeline(messageEvent, liveTimeline, {
+ toStartOfTimeline: true,
+ });
+ expect(liveTimeline.getEvents().length).toStrictEqual(0);
+ });
  });
 
  describe('aggregateRelations', () => {

src/models/event-timeline-set.ts

@@ -702,6 +702,19 @@ export class EventTimelineSet extends TypedEventEmitter<EmittedEvents, EventTime
  );
  }
 
+ if (timeline.getTimelineSet() !== this) {
+ throw new Error(`EventTimelineSet.addEventToTimeline: Timeline=${timeline.toString()} does not belong " + 
+ "in timelineSet(threadId=${this.thread?.id})`);
+ }
+
+ // Make sure events don't get mixed in timelines they shouldn't be in
+ // (e.g. a threaded message should not be in the main timeline).
+ if (!this.canContain(event)) {
+ logger.warn(`EventTimelineSet.addEventToTimeline: Ignoring event=${event.getId()} that does not belong " + 
+ "in timeline=${timeline.toString()} timelineSet(threadId=${this.thread?.id})`);
+ return;
+ }
+
  const eventId = event.getId()!;
  timeline.addEvent(event, {
  toStartOfTimeline,