Ignore edits in message previews when they concern messages other than latest

src/stores/room-list/MessagePreviewStore.ts

@@ -18,6 +18,7 @@ import { Room } from "matrix-js-sdk/src/models/room";
 import { isNullOrUndefined } from "matrix-js-sdk/src/utils";
 import { MatrixEvent } from "matrix-js-sdk/src/models/event";
 import { M_POLL_START } from "matrix-js-sdk/src/@types/polls";
+import { RelationType } from "matrix-js-sdk/src/matrix";
 
 import { ActionPayload } from "../../dispatcher/payloads";
 import { AsyncStoreWithClient } from "../AsyncStoreWithClient";
@@ -102,8 +103,15 @@ export class MessagePreviewStore extends AsyncStoreWithClient<IState> {
         return instance;
     })();
 
+    /**
+     * @internal Public for test only
+     */
+    public static testInstance(): MessagePreviewStore {
+        return new MessagePreviewStore();
+    }
+
     // null indicates the preview is empty / irrelevant
-    private previews = new Map<string, Map<TagID | TAG_ANY, string | null>>();
+    private previews = new Map<string, Map<TagID | TAG_ANY, [MatrixEvent, string] | null>>();
 
     private constructor() {
         super(defaultDispatcher, {});
@@ -131,27 +139,44 @@ export class MessagePreviewStore extends AsyncStoreWithClient<IState> {
         const previews = this.previews.get(room.roomId);
         if (!previews) return null;
 
-        if (!previews.has(inTagId)) {
-            return previews.get(TAG_ANY)!;
+        if (previews.has(inTagId)) {
+            return previews.get(inTagId)![1];
         }
-        return previews.get(inTagId) ?? null;
+        return previews.get(TAG_ANY)?.[1] ?? null;
     }
 
     public generatePreviewForEvent(event: MatrixEvent): string {
         const previewDef = PREVIEWS[event.getType()];
         return previewDef?.previewer.getTextFor(event, undefined, true) ?? "";
     }
 
+    private shouldSkipPreview(event: MatrixEvent, previousEvent?: MatrixEvent): boolean {
+        if (event.isRelation(RelationType.Replace)) {
+            if (previousEvent !== undefined) {
+                // Ignore edits if they don't apply to the latest event in the room to keep the preview on the latest event
+                const room = this.matrixClient?.getRoom(event.getRoomId()!);
+                const relatedEvent = room?.findEventById(event.relationEventId!);
+                if (relatedEvent !== previousEvent) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
     private async generatePreview(room: Room, tagId?: TagID): Promise<void> {
         const events = room.timeline;
         if (!events) return; // should only happen in tests
 
         let map = this.previews.get(room.roomId);
         if (!map) {
-            map = new Map<TagID | TAG_ANY, string | null>();
+            map = new Map<TagID | TAG_ANY, [MatrixEvent, string] | null>();
             this.previews.set(room.roomId, map);
         }
 
+        const previousEventInAny = map.get(TAG_ANY)?.[0];
+
         // Set the tags so we know what to generate
         if (!map.has(TAG_ANY)) map.set(TAG_ANY, null);
         if (tagId && !map.has(tagId)) map.set(tagId, null);
@@ -174,19 +199,24 @@ export class MessagePreviewStore extends AsyncStoreWithClient<IState> {
             const anyPreview = previewDef.previewer.getTextFor(event);
             if (!anyPreview) continue; // not previewable for some reason
 
-            changed = changed || anyPreview !== map.get(TAG_ANY);
-            map.set(TAG_ANY, anyPreview);
+            if (!this.shouldSkipPreview(event, previousEventInAny)) {
+                changed = changed || anyPreview !== map.get(TAG_ANY)?.[1];
+                map.set(TAG_ANY, [event, anyPreview]);
+            }
 
             const tagsToGenerate = Array.from(map.keys()).filter((t) => t !== TAG_ANY); // we did the any tag above
             for (const genTagId of tagsToGenerate) {
+                const previousEventInTag = map.get(genTagId)?.[0];
+                if (this.shouldSkipPreview(event, previousEventInTag)) continue;
+
                 const realTagId = genTagId === TAG_ANY ? undefined : genTagId;
                 const preview = previewDef.previewer.getTextFor(event, realTagId);
                 if (preview === anyPreview) {
-                    changed = changed || anyPreview !== map.get(genTagId);
+                    changed = changed || anyPreview !== map.get(genTagId)?.[1];
                     map.delete(genTagId);
                 } else {
-                    changed = changed || preview !== map.get(genTagId);
-                    map.set(genTagId, preview);
+                    changed = changed || preview !== map.get(genTagId)?.[1];
+                    map.set(genTagId, preview ? [event, preview] : null);
                 }
             }
 
@@ -200,7 +230,7 @@ export class MessagePreviewStore extends AsyncStoreWithClient<IState> {
         }
 
         // At this point, we didn't generate a preview so clear it
-        this.previews.set(room.roomId, new Map<TagID | TAG_ANY, string | null>());
+        this.previews.set(room.roomId, new Map<TagID | TAG_ANY, [MatrixEvent, string] | null>());
         this.emit(UPDATE_EVENT, this);
         this.emit(MessagePreviewStore.getPreviewChangedEventName(room), room);
     }

test/stores/room-list/MessagePreviewStore-test.ts

@@ -0,0 +1,95 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { mocked } from "jest-mock";
+import { EventType, MatrixEvent, RelationType, Room } from "matrix-js-sdk/src/matrix";
+
+import { MessagePreviewStore } from "../../../src/stores/room-list/MessagePreviewStore";
+import { mkEvent, mkMessage, mkStubRoom, setupAsyncStoreWithClient, stubClient } from "../../test-utils";
+import { DefaultTagID } from "../../../src/stores/room-list/models";
+
+describe("MessagePreviewStore", () => {
+    async function addEvent(store: MessagePreviewStore, room: Room, event: MatrixEvent): Promise<void> {
+        room.timeline.push(event);
+        mocked(room.findEventById).mockImplementation((eventId) => room.timeline.find((e) => e.getId() === eventId));
+        // @ts-ignore private access
+        await store.onAction({
+            action: "MatrixActions.Room.timeline",
+            event,
+            isLiveEvent: true,
+            isLiveUnfilteredRoomTimelineEvent: true,
+            room,
+        });
+    }
+
+    it("should ignore edits for events other than the latest one", async () => {
+        const client = stubClient();
+        const room = mkStubRoom("!roomId:server", "Room", client);
+        mocked(client.getRoom).mockReturnValue(room);
+
+        const store = MessagePreviewStore.testInstance();
+        await store.start();
+        await setupAsyncStoreWithClient(store, client);
+
+        await expect(store.getPreviewForRoom(room, DefaultTagID.Untagged)).resolves.toMatchInlineSnapshot(`null`);
+
+        const firstMessage = mkMessage({
+            user: "@sender:server",
+            event: true,
+            room: room.roomId,
+            msg: "First message",
+        });
+        await addEvent(store, room, firstMessage);
+
+        await expect(store.getPreviewForRoom(room, DefaultTagID.Untagged)).resolves.toMatchInlineSnapshot(
+            `"@sender:server: First message"`,
+        );
+
+        const secondMessage = mkMessage({
+            user: "@sender:server",
+            event: true,
+            room: room.roomId,
+            msg: "Second message",
+        });
+        await addEvent(store, room, secondMessage);
+
+        await expect(store.getPreviewForRoom(room, DefaultTagID.Untagged)).resolves.toMatchInlineSnapshot(
+            `"@sender:server: Second message"`,
+        );
+
+        const firstMessageEdit = mkEvent({
+            event: true,
+            type: EventType.RoomMessage,
+            user: "@sender:server",
+            room: room.roomId,
+            content: {
+                "body": "* First Message Edit",
+                "m.new_content": {
+                    body: "First Message Edit",
+                },
+                "m.relates_to": {
+                    rel_type: RelationType.Replace,
+                    event_id: firstMessage.getId()!,
+                },
+            },
+        });
+        await addEvent(store, room, firstMessageEdit);
+
+        await expect(store.getPreviewForRoom(room, DefaultTagID.Untagged)).resolves.toMatchInlineSnapshot(
+            `"@sender:server: Second message"`,
+        );
+    });
+});