remove polls from room state on redaction (#3475)

spec/unit/room.spec.ts

@@ -55,6 +55,7 @@ import * as threadUtils from "../test-utils/thread";
 import { getMockClientWithEventEmitter, mockClientMethodsUser } from "../test-utils/client";
 import { logger } from "../../src/logger";
 import { IMessageOpts } from "../test-utils/test-utils";
+import { flushPromises } from "../test-utils/flushPromises";
 
 describe("Room", function () {
     const roomId = "!foo:bar";
@@ -3388,6 +3389,23 @@ describe("Room", function () {
             const poll = room.polls.get(pollStartEventId);
             expect(poll?.pollId).toBe(pollStartEventId);
         });
+
+        it("removes poll from state when redacted", async () => {
+            const pollStartEvent = makePollStart("1");
+            const events = [pollStartEvent];
+
+            await room.processPollEvents(events);
+
+            expect(room.polls.get(pollStartEvent.getId()!)).toBeTruthy();
+
+            const redactedEvent = new MatrixEvent({ type: "m.room.redaction" });
+            pollStartEvent.makeRedacted(redactedEvent);
+
+            await flushPromises();
+
+            // removed from poll state
+            expect(room.polls.get(pollStartEvent.getId()!)).toBeFalsy();
+        });
     });
 
     describe("findPredecessorRoomId", () => {

src/models/room.ts

@@ -2008,6 +2008,11 @@ export class Room extends ReadReceipt<RoomEmittedEvents, RoomEventHandlerMap> {
                 const poll = new Poll(event, this.client, this);
                 this.polls.set(event.getId()!, poll);
                 this.emit(PollEvent.New, poll);
+
+                // remove the poll when redacted
+                event.once(MatrixEventEvent.BeforeRedaction, (redactedEvent: MatrixEvent) => {
+                    this.polls.delete(redactedEvent.getId()!);
+                });
             } catch {}
             // poll creation can fail for malformed poll start events
             return;