Don't form continuations from thread roots (#8166)

* Don't form continuations from thread roots

* Only apply the continuation break in the main timeline

test/components/structures/MessagePanel-test.js

@@ -25,6 +25,7 @@ import * as TestUtils from "react-dom/test-utils";
 
 import { MatrixClientPeg } from '../../../src/MatrixClientPeg';
 import sdk from '../../skinned-sdk';
+import MessagePanel, { shouldFormContinuation } from "../../../src/components/structures/MessagePanel";
 import SettingsStore from "../../../src/settings/SettingsStore";
 import MatrixClientContext from "../../../src/contexts/MatrixClientContext";
 import RoomContext from "../../../src/contexts/RoomContext";
@@ -32,8 +33,6 @@ import DMRoomMap from "../../../src/utils/DMRoomMap";
 import { UnwrappedEventTile } from "../../../src/components/views/rooms/EventTile";
 import * as TestUtilsMatrix from "../../test-utils";
 
-const MessagePanel = sdk.getComponent('structures.MessagePanel');
-
 let client;
 const room = new Matrix.Room("!roomId:server_name");
 
@@ -594,3 +593,25 @@ describe('MessagePanel', function() {
         expect(els.last().prop("events").length).toEqual(5);
     });
 });
+
+describe("shouldFormContinuation", () => {
+    it("does not form continuations from thread roots", () => {
+        const threadRoot = TestUtilsMatrix.mkMessage({
+            event: true,
+            room: "!room:id",
+            user: "@user:id",
+            msg: "Here is a thread",
+        });
+        jest.spyOn(threadRoot, "isThreadRoot", "get").mockReturnValue(true);
+
+        const message = TestUtilsMatrix.mkMessage({
+            event: true,
+            room: "!room:id",
+            user: "@user:id",
+            msg: "And here's another message in the main timeline",
+        });
+
+        expect(shouldFormContinuation(threadRoot, message, false, true)).toEqual(false);
+        expect(shouldFormContinuation(message, threadRoot, false, true)).toEqual(true);
+    });
+});

test/test-utils/test-utils.ts

@@ -191,7 +191,20 @@ export function mkEvent(opts: MakeEventProps): MatrixEvent {
     ].indexOf(opts.type) !== -1) {
         event.state_key = "";
     }
-    return opts.event ? new MatrixEvent(event) : event as unknown as MatrixEvent;
+
+    const mxEvent = opts.event ? new MatrixEvent(event) : event as unknown as MatrixEvent;
+    if (!mxEvent.sender && opts.user && opts.room) {
+        mxEvent.sender = {
+            userId: opts.user,
+            membership: "join",
+            name: opts.user,
+            rawDisplayName: opts.user,
+            roomId: opts.room,
+            getAvatarUrl: () => {},
+            getMxcAvatarUrl: () => {},
+        } as unknown as RoomMember;
+    }
+    return mxEvent;
 }
 
 /**