Fix issues around up arrow event edit shortcut (#9645)

src/components/structures/RoomView.tsx

@@ -25,7 +25,6 @@ import { logger } from "matrix-js-sdk/src/logger";
 import { EventTimeline } from 'matrix-js-sdk/src/models/event-timeline';
 import { EventType } from 'matrix-js-sdk/src/@types/event';
 import { RoomState, RoomStateEvent } from 'matrix-js-sdk/src/models/room-state';
-import { EventTimelineSet } from "matrix-js-sdk/src/models/event-timeline-set";
 import { CallState, MatrixCall } from "matrix-js-sdk/src/webrtc/call";
 import { throttle } from "lodash";
 import { MatrixError } from 'matrix-js-sdk/src/http-api';
@@ -1211,10 +1210,14 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
         });
     };
 
-    private onRoomTimelineReset = (room: Room, timelineSet: EventTimelineSet) => {
-        if (!room || room.roomId !== this.state.room?.roomId) return;
+    private onRoomTimelineReset = (room?: Room): void => {
+        if (room &&
+            room.roomId === this.state.room?.roomId &&
+            room.getLiveTimeline() !== this.state.liveTimeline
+        ) {
             logger.log(`Live timeline of ${room.roomId} was reset`);
-        this.setState({ liveTimeline: timelineSet.getLiveTimeline() });
+            this.setState({ liveTimeline: room.getLiveTimeline() });
+        }
     };
 
     private getRoomTombstone(room = this.state.room) {

src/utils/EventUtils.ts

@@ -110,7 +110,8 @@ export function findEditableEvent({
     events: MatrixEvent[];
     isForward: boolean;
     fromEventId?: string;
-}): MatrixEvent {
+}): MatrixEvent | undefined {
+    if (!events.length) return;
     const maxIdx = events.length - 1;
     const inc = isForward ? 1 : -1;
     const beginIdx = isForward ? 0 : maxIdx;

test/utils/EventUtils-test.ts

@@ -34,6 +34,7 @@ import {
     canEditContent,
     canEditOwnEvent,
     fetchInitialEvent,
+    findEditableEvent,
     isContentActionable,
     isLocationEvent,
     isVoiceMessage,
@@ -430,4 +431,13 @@ describe('EventUtils', () => {
             expect(room.getThread(THREAD_ROOT)).toBeInstanceOf(Thread);
         });
     });
+
+    describe("findEditableEvent", () => {
+        it("should not explode when given empty events array", () => {
+            expect(findEditableEvent({
+                events: [],
+                isForward: true,
+            })).toBeUndefined();
+        });
+    });
 });