From 1da26b5cd199650f77bf3f62a60d84b9add5e270 Mon Sep 17 00:00:00 2001
From: Michael Telatynski <7t3chguy@gmail.com>
Date: Fri, 10 Jan 2025 10:16:45 +0000
Subject: [PATCH] Fix issue with sentinels being incorrect on m.room.member
 events (#4609)

* Fix issue with sentinels being incorrect on m.room.member events

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Simplify change

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Add test

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

---------

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>
---
 spec/unit/event-timeline-set.spec.ts | 26 +++++++++++++++
 src/client.ts                        |  4 +--
 src/models/event-timeline.ts         | 22 +------------
 src/models/event.ts                  | 49 ++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 24 deletions(-)

diff --git a/spec/unit/event-timeline-set.spec.ts b/spec/unit/event-timeline-set.spec.ts
index 61b30edb36d..352e882130c 100644
--- a/spec/unit/event-timeline-set.spec.ts
+++ b/spec/unit/event-timeline-set.spec.ts
@@ -23,6 +23,7 @@ import {
     EventTimelineSet,
     EventType,
     Filter,
+    KnownMembership,
     MatrixClient,
     MatrixEvent,
     MatrixEventEvent,
@@ -138,6 +139,31 @@ describe("EventTimelineSet", () => {
             expect(eventsInLiveTimeline.length).toStrictEqual(1);
             expect(eventsInLiveTimeline[0]).toStrictEqual(duplicateMessageEvent);
         });
+
+        it("should set event.target after applying the membership state update", () => {
+            const eventTimelineSet = room.getUnfilteredTimelineSet();
+
+            const ev1 = utils.mkMembership({
+                room: roomId,
+                mship: KnownMembership.Invite,
+                user: "@sender:server",
+                skey: userA,
+                event: true,
+            });
+            const ev2 = utils.mkMembership({
+                room: roomId,
+                mship: KnownMembership.Join,
+                user: userA,
+                skey: userA,
+                name: "This is my displayname",
+                event: true,
+            });
+
+            eventTimelineSet.addLiveEvent(ev1, { addToState: true });
+            expect(ev1.target?.name).toBe(userA);
+            eventTimelineSet.addLiveEvent(ev2, { addToState: true });
+            expect(ev2.target?.name).toBe("This is my displayname");
+        });
     });
 
     describe("addEventToTimeline", () => {
diff --git a/src/client.ts b/src/client.ts
index eea8faa708f..0e49b16091c 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -7348,10 +7348,8 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             const sr = SearchResult.fromJson(roomEvents.results![i], mapper);
             const room = this.getRoom(sr.context.getEvent().getRoomId());
             if (room) {
-                // Copy over a known event sender if we can
                 for (const ev of sr.context.getTimeline()) {
-                    const sender = room.getMember(ev.getSender()!);
-                    if (!ev.sender && sender) ev.sender = sender;
+                    ev.setMetadata(room.currentState, false);
                 }
             }
             searchResults.results.push(sr);
diff --git a/src/models/event-timeline.ts b/src/models/event-timeline.ts
index cb2ce372259..0cc7ceac267 100644
--- a/src/models/event-timeline.ts
+++ b/src/models/event-timeline.ts
@@ -68,27 +68,7 @@ export class EventTimeline {
      * @param toStartOfTimeline -  if true the event's forwardLooking flag is set false
      */
     public static setEventMetadata(event: MatrixEvent, stateContext: RoomState, toStartOfTimeline: boolean): void {
-        // When we try to generate a sentinel member before we have that member
-        // in the members object, we still generate a sentinel but it doesn't
-        // have a membership event, so test to see if events.member is set. We
-        // check this to avoid overriding non-sentinel members by sentinel ones
-        // when adding the event to a filtered timeline
-        if (!event.sender?.events?.member) {
-            event.sender = stateContext.getSentinelMember(event.getSender()!);
-        }
-        if (!event.target?.events?.member && event.getType() === EventType.RoomMember) {
-            event.target = stateContext.getSentinelMember(event.getStateKey()!);
-        }
-
-        if (event.isState()) {
-            // room state has no concept of 'old' or 'current', but we want the
-            // room state to regress back to previous values if toStartOfTimeline
-            // is set, which means inspecting prev_content if it exists. This
-            // is done by toggling the forwardLooking flag.
-            if (toStartOfTimeline) {
-                event.forwardLooking = false;
-            }
-        }
+        event.setMetadata(stateContext, toStartOfTimeline);
     }
 
     private readonly roomId: string | null;
diff --git a/src/models/event.ts b/src/models/event.ts
index 9e52e0d9365..6aea68d5e4e 100644
--- a/src/models/event.ts
+++ b/src/models/event.ts
@@ -48,6 +48,7 @@ import { Room } from "./room.ts";
 import { EventTimeline } from "./event-timeline.ts";
 import { Membership } from "../@types/membership.ts";
 import { DecryptionFailureCode } from "../crypto-api/index.ts";
+import { RoomState } from "./room-state.ts";
 
 export { EventStatus } from "./event-status.ts";
 
@@ -232,6 +233,7 @@ export enum MatrixEventEvent {
     Status = "Event.status",
     Replaced = "Event.replaced",
     RelationsCreated = "Event.relationsCreated",
+    SentinelUpdated = "Event.sentinelUpdated",
 }
 
 export type MatrixEventEmittedEvents = MatrixEventEvent | ThreadEvent.Update;
@@ -244,6 +246,7 @@ export type MatrixEventHandlerMap = {
     [MatrixEventEvent.Status]: (event: MatrixEvent, status: EventStatus | null) => void;
     [MatrixEventEvent.Replaced]: (event: MatrixEvent) => void;
     [MatrixEventEvent.RelationsCreated]: (relationType: string, eventType: string) => void;
+    [MatrixEventEvent.SentinelUpdated]: () => void;
 } & Pick<ThreadEventHandlerMap, ThreadEvent.Update>;
 
 export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, MatrixEventHandlerMap> {
@@ -328,6 +331,7 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
      * Should be read-only
      */
     public sender: RoomMember | null = null;
+
     /**
      * The room member who is the target of this event, e.g.
      * the invitee, the person being banned, etc.
@@ -335,6 +339,51 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
      * Should be read-only
      */
     public target: RoomMember | null = null;
+
+    /**
+     * Update the sentinels and forwardLooking flag for this event.
+     * @param stateContext -  the room state to be queried
+     * @param toStartOfTimeline -  if true the event's forwardLooking flag is set false
+     * @internal
+     */
+    public setMetadata(stateContext: RoomState, toStartOfTimeline: boolean): void {
+        // If an event is an m.room.member state event then we should set the sentinels again in case setEventMetadata
+        // was already called before the state was applied and thus the sentinel points at the member from before this event.
+        const affectsSelf =
+            this.isState() && this.getType() === EventType.RoomMember && this.getSender() === this.getStateKey();
+
+        let changed = false;
+        // When we try to generate a sentinel member before we have that member
+        // in the members object, we still generate a sentinel but it doesn't
+        // have a membership event, so test to see if events.member is set. We
+        // check this to avoid overriding non-sentinel members by sentinel ones
+        // when adding the event to a filtered timeline
+        if (affectsSelf || !this.sender?.events?.member) {
+            const newSender = stateContext.getSentinelMember(this.getSender()!);
+            if (newSender !== this.sender) changed = true;
+            this.sender = newSender;
+        }
+        if (affectsSelf || (!this.target?.events?.member && this.getType() === EventType.RoomMember)) {
+            const newTarget = stateContext.getSentinelMember(this.getStateKey()!);
+            if (newTarget !== this.target) changed = true;
+            this.target = newTarget;
+        }
+
+        if (this.isState()) {
+            // room state has no concept of 'old' or 'current', but we want the
+            // room state to regress back to previous values if toStartOfTimeline
+            // is set, which means inspecting prev_content if it exists. This
+            // is done by toggling the forwardLooking flag.
+            if (toStartOfTimeline) {
+                this.forwardLooking = false;
+            }
+        }
+
+        if (changed) {
+            this.emit(MatrixEventEvent.SentinelUpdated);
+        }
+    }
+
     /**
      * The sending status of the event.
      * @privateRemarks