Fix getLatestTimeline not working when the latest even in the room wa…

…s a threaded message

See matrix-org/matrix-react-sdk#8354 (comment)

Also have to keep in mind that we don't want to mix messages in the wrong timelines (main vs threaded timeline)

 - #2444
 - #2454

.gitignore

@@ -6,6 +6,7 @@ node_modules
 /*.log
 package-lock.json
 .lock-wscript
+.DS_Store
 build/Release
 coverage
 lib-cov

spec/integ/matrix-client-room-timeline.spec.js

@@ -688,7 +688,7 @@ describe("MatrixClient room timelines", function() {
                 });
 
             // Wait for the timeline to reset(when it goes blank) which means
-            // it's in the middle of the refrsh logic right before the
+            // it's in the middle of the refresh logic right before the
             // `getEventTimeline()` -> `/context`. Then simulate a racey `/sync`
             // to happen in the middle of all of this refresh timeline logic. We
             // want to make sure the sync pagination still works as expected

src/client.ts

@@ -5288,10 +5288,6 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         ];
 
         if (this.supportsExperimentalThreads()) {
-            if (!timelineSet.canContain(event)) {
-                return undefined;
-            }
-
             // Where the event is a thread reply (not a root) and running in MSC-enabled mode the Thread timeline only
             // functions contiguously, so we have to jump through some hoops to get our target event in it.
             // XXX: workaround for https://github.com/vector-im/element-meta/issues/150

src/models/event-timeline-set.ts

@@ -691,6 +691,18 @@ 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,

src/models/room.ts

@@ -981,6 +981,10 @@ export class Room extends TypedEventEmitter<EmittedEvents, RoomEventHandlerMap>
             newTimeline = await this.client.getEventTimeline(timelineSet, mostRecentEventInTimeline.getId());
         }
 
+        if (!newTimeline) {
+            throw new Error(`[refreshLiveTimeline for ${this.roomId}] No new timeline created`);
+        }
+
         // If a racing `/sync` beat us to creating a new timeline, use that
         // instead because it's the latest in the room and any new messages in
         // the scrollback will include the history.