Fix threads fallback incorrectly targets root event

src/components/structures/ThreadView.tsx

@@ -16,7 +16,7 @@ limitations under the License.
 
 import React, { createRef, KeyboardEvent } from 'react';
 import { Thread, THREAD_RELATION_TYPE, ThreadEvent } from 'matrix-js-sdk/src/models/thread';
-import { Room } from 'matrix-js-sdk/src/models/room';
+import { Room, RoomEvent } from 'matrix-js-sdk/src/models/room';
 import { IEventRelation, MatrixEvent } from 'matrix-js-sdk/src/models/event';
 import { TimelineWindow } from 'matrix-js-sdk/src/timeline-window';
 import { Direction } from 'matrix-js-sdk/src/models/event-timeline';
@@ -69,6 +69,7 @@ interface IProps {
 
 interface IState {
     thread?: Thread;
+    lastReply?: MatrixEvent | null;
     layout: Layout;
     editState?: EditorStateTransfer;
     replyToEvent?: MatrixEvent;
@@ -188,13 +189,31 @@ export default class ThreadView extends React.Component<IProps, IState> {
         }
     };
 
+    private updateThreadRelation = (): void => {
+        this.setState({
+            lastReply: this.state.thread?.lastReply((ev: MatrixEvent) => {
+                return ev.isRelation(THREAD_RELATION_TYPE.name) && !ev.status;
+            }),
+        });
+    };
+
     private updateThread = (thread?: Thread) => {
         if (thread && this.state.thread !== thread) {
+            if (this.state.thread) {
+                this.state.thread.off(ThreadEvent.NewReply, this.updateThreadRelation);
+                this.props.room.off(RoomEvent.LocalEchoUpdated, this.updateThreadRelation);
+            }
+            thread.on(ThreadEvent.NewReply, this.updateThreadRelation);
+            this.props.room.on(RoomEvent.LocalEchoUpdated, this.updateThreadRelation);
             this.setState({
                 thread,
+                lastReply: thread?.lastReply((ev: MatrixEvent) => {
+                    return ev.isRelation(THREAD_RELATION_TYPE.name) && !ev.status;
+                }),
             }, async () => {
                 thread.emit(ThreadEvent.ViewThread);
                 await thread.fetchInitialEvents();
+                this.updateThreadRelation();
                 this.nextBatch = thread.liveTimeline.getPaginationToken(Direction.Backward);
                 this.timelinePanel.current?.refreshTimeline();
             });
@@ -241,14 +260,14 @@ export default class ThreadView extends React.Component<IProps, IState> {
         }
     };
 
-    private nextBatch: string;
+    private nextBatch: string | undefined | null = null;
 
     private onPaginationRequest = async (
         timelineWindow: TimelineWindow | null,
         direction = Direction.Backward,
         limit = 20,
     ): Promise<boolean> => {
-        if (!Thread.hasServerSideSupport) {
+        if (!Thread.hasServerSideSupport && timelineWindow) {
             timelineWindow.extend(direction, limit);
             return true;
         }
@@ -261,40 +280,50 @@ export default class ThreadView extends React.Component<IProps, IState> {
             opts.from = this.nextBatch;
         }
 
-        const { nextBatch } = await this.state.thread.fetchEvents(opts);
-
-        this.nextBatch = nextBatch;
+        let nextBatch: string | null = null;
+        if (this.state.thread) {
+            const response = await this.state.thread.fetchEvents(opts);
+            nextBatch = response.nextBatch;
+            this.nextBatch = nextBatch;
+        }
 
         // Advances the marker on the TimelineWindow to define the correct
         // window of events to display on screen
-        timelineWindow.extend(direction, limit);
+        timelineWindow?.extend(direction, limit);
 
         return !!nextBatch;
     };
 
     private onFileDrop = (dataTransfer: DataTransfer) => {
-        ContentMessages.sharedInstance().sendContentListToRoom(
-            Array.from(dataTransfer.files),
-            this.props.mxEvent.getRoomId(),
-            this.threadRelation,
-            MatrixClientPeg.get(),
-            TimelineRenderingType.Thread,
-        );
+        const roomId = this.props.mxEvent.getRoomId();
+        if (roomId) {
+            ContentMessages.sharedInstance().sendContentListToRoom(
+                Array.from(dataTransfer.files),
+                roomId,
+                this.threadRelation,
+                MatrixClientPeg.get(),
+                TimelineRenderingType.Thread,
+            );
+        } else {
+            console.warn("Unknwon roomId for event", this.props.mxEvent);
+        }
     };
 
     private get threadRelation(): IEventRelation {
-        const lastThreadReply = this.state.thread?.lastReply((ev: MatrixEvent) => {
-            return ev.isRelation(THREAD_RELATION_TYPE.name) && !ev.status;
-        });
-
-        return {
+        const relation = {
             "rel_type": THREAD_RELATION_TYPE.name,
             "event_id": this.state.thread?.id,
             "is_falling_back": true,
-            "m.in_reply_to": {
-                "event_id": lastThreadReply?.getId() ?? this.state.thread?.id,
-            },
         };
+
+        const fallbackEventId = this.state.lastReply?.getId() ?? this.state.thread?.id;
+        if (fallbackEventId) {
+            relation["m.in_reply_to"] = {
+                "event_id": fallbackEventId,
+            };
+        }
+
+        return relation;
     }
 
     private renderThreadViewHeader = (): JSX.Element => {

src/components/views/context_menus/ThreadListContextMenu.tsx

@@ -31,7 +31,7 @@ import { ViewRoomPayload } from "../../../dispatcher/payloads/ViewRoomPayload";
 
 interface IProps {
     mxEvent: MatrixEvent;
-    permalinkCreator: RoomPermalinkCreator;
+    permalinkCreator?: RoomPermalinkCreator;
     onMenuToggle?: (open: boolean) => void;
 }
 
@@ -64,12 +64,14 @@ const ThreadListContextMenu: React.FC<IProps> = ({
         closeThreadOptions();
     }, [mxEvent, closeThreadOptions]);
 
-    const copyLinkToThread = useCallback(async (evt: ButtonEvent) => {
-        evt.preventDefault();
-        evt.stopPropagation();
-        const matrixToUrl = permalinkCreator.forEvent(mxEvent.getId());
-        await copyPlaintext(matrixToUrl);
-        closeThreadOptions();
+    const copyLinkToThread = useCallback(async (evt: ButtonEvent | undefined) => {
+        if (permalinkCreator) {
+            evt?.preventDefault();
+            evt?.stopPropagation();
+            const matrixToUrl = permalinkCreator.forEvent(mxEvent.getId());
+            await copyPlaintext(matrixToUrl);
+            closeThreadOptions();
+        }
     }, [mxEvent, closeThreadOptions, permalinkCreator]);
 
     useEffect(() => {
@@ -102,11 +104,13 @@ const ThreadListContextMenu: React.FC<IProps> = ({
                      label={_t("View in room")}
                      iconClassName="mx_ThreadPanel_viewInRoom"
                  /> }
-                <IconizedContextMenuOption
-                    onClick={(e) => copyLinkToThread(e)}
-                    label={_t("Copy link to thread")}
-                    iconClassName="mx_ThreadPanel_copyLinkToThread"
-                />
+                { permalinkCreator &&
+                    <IconizedContextMenuOption
+                        onClick={(e) => copyLinkToThread(e)}
+                        label={_t("Copy link to thread")}
+                        iconClassName="mx_ThreadPanel_copyLinkToThread"
+                    />
+                }
             </IconizedContextMenuOptionList>
         </IconizedContextMenu>) }
     </React.Fragment>;

src/components/views/elements/Tooltip.tsx

@@ -56,7 +56,7 @@ type State = Partial<Pick<CSSProperties, "display" | "right" | "top" | "transfor
 
 export default class Tooltip extends React.PureComponent<ITooltipProps, State> {
     private static container: HTMLElement;
-    private parent: Element;
+    private parent: Element | null = null;
 
     // XXX: This is because some components (Field) are unable to `import` the Tooltip class,
     // so we expose the Alignment options off of us statically.
@@ -86,7 +86,7 @@ export default class Tooltip extends React.PureComponent<ITooltipProps, State> {
             capture: true,
         });
 
-        this.parent = ReactDOM.findDOMNode(this).parentNode as Element;
+        this.parent = ReactDOM.findDOMNode(this)?.parentNode as Element ?? null;
 
         this.updatePosition();
     }

test/components/views/rooms/SendMessageComposer-test.tsx

@@ -17,7 +17,7 @@ limitations under the License.
 import React from "react";
 import { act } from "react-dom/test-utils";
 import { sleep } from "matrix-js-sdk/src/utils";
-import { ISendEventResponse, MatrixClient, MsgType } from "matrix-js-sdk/src/matrix";
+import { ISendEventResponse, MatrixClient, MsgType, RelationType } from "matrix-js-sdk/src/matrix";
 // eslint-disable-next-line deprecate/import
 import { mount } from 'enzyme';
 import { mocked } from "jest-mock";
@@ -303,7 +303,7 @@ describe('<SendMessageComposer/>', () => {
 
         it('correctly sets the editorStateKey for threads', () => {
             const relation = {
-                rel_type: "m.thread",
+                rel_type: RelationType.Thread,
                 event_id: "myFakeThreadId",
             };
             const includeReplyLegacyFallback = false;

test/test-utils/threads.ts

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { MatrixEvent, Room } from "matrix-js-sdk/src/matrix";
+import { MatrixEvent, RelationType, Room } from "matrix-js-sdk/src/matrix";
 
 import { mkMessage, MessageEventProps } from "./test-utils";
 
@@ -78,7 +78,7 @@ export const makeThreadEvents = ({
 
     rootEvent.setUnsigned({
         "m.relations": {
-            "m.thread": {
+            [RelationType.Thread]: {
                 latest_event: events[events.length - 1],
                 count: length,
                 current_user_participated: [...participantUserIds, authorId].includes(currentUserId),