clear all room state before rejoining room

src/matrix/room/Room.js

@@ -251,6 +251,9 @@ export class Room extends EventEmitter {
         log.set("id", this.id);
         const isRejoin = summaryChanges.membership === "join" && this.membership !== "join";
         if (isRejoin) {
+            // remove all room state before calling syncWriter,
+            // so no old state sticks around
+            txn.roomState.removeAllForRoom(this.id);
             this._summary.tryRemoveArchive(txn);
         }
         const {entries: newEntries, newLiveKey, memberChanges} =

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

@@ -14,17 +14,19 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+const MAX_UNICODE = "\u{10FFFF}";
+
 export class RoomStateStore {
 	constructor(idbStore) {
 		this._roomStateStore = idbStore;
 	}
 
 	async getAllForType(type) {
-
+		throw new Error("unimplemented");
 	}
 
 	async get(type, stateKey) {
-        
+        throw new Error("unimplemented");
 	}
 
 	async set(roomId, event) {
@@ -32,4 +34,11 @@ export class RoomStateStore {
         const entry = {roomId, event, key};
 		return this._roomStateStore.put(entry);
 	}
+
+	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._roomStateStore.delete(range);
+	}
 }