clear all room state when rejoining room

src/matrix/room/Room.js

@@ -254,6 +254,7 @@ export class Room extends EventEmitter {
             // remove all room state before calling syncWriter,
             // so no old state sticks around
             txn.roomState.removeAllForRoom(this.id);
+            txn.roomMembers.removeAllForRoom(this.id);
             txn.archivedRoomSummary.remove(this.id);
         }
         const {entries: newEntries, newLiveKey, memberChanges} =

src/matrix/storage/idb/stores/RoomMemberStore.js

@@ -1,6 +1,6 @@
 /*
 Copyright 2020 Bruno Windels <bruno@windels.cloud>
-Copyright 2020 The Matrix.org Foundation C.I.C.
+Copyright 2020, 2021 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.
@@ -15,6 +15,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import {MAX_UNICODE} from "./common.js";
+
 function encodeKey(roomId, userId) {
     return `${roomId}|${userId}`;
 }
@@ -60,4 +62,11 @@ export class RoomMemberStore {
         });
         return userIds;
     }
+
+    removeAllForRoom(roomId) {
+        // exclude both keys as they are theoretical min and max,
+        // but we should't have a match for just the room id, or room id with max
+        const range = IDBKeyRange.bound(roomId, `${roomId}|${MAX_UNICODE}`, true, true);
+        this._roomMembersStore.delete(range);
+    }
 }