feat: emit error on connections when receiving "EXPIRE"

Closes #924

Author: WofWca

lib/peer.ts

@@ -392,6 +392,22 @@ export class Peer extends EventEmitter<PeerEvents> {
 					PeerErrorType.PeerUnavailable,
 					`Could not connect to peer ${peerId}`,
 				);
+
+				// This is so that an error is emited on a connection that has just been created,
+				// but could not be established because the server responded with
+				// `ServerMessageType.Expire` (but yes, we emit the error on all connections).
+				// See https://github.com/peers/peerjs/issues/924
+				//
+				// TODO how about `this._cleanupPeer(peerId);` instead?
+				// Or how about make the server send back `connectionId`, and only emit the error
+				// on that connection?
+				const connections = this._connections.get(peerId);
+				if (connections) {
+					for (const c of connections) {
+						c.emit("error", new Error(`Server says ${peerId} is unavailable`);
+					}
+				}
+
 				break;
 			case ServerMessageType.Offer: {
 				// we should consider switching this to CALL/CONNECT, but this is the least breaking option.