lib/client: reject Client.roundtrip promise on disconnect

lib/client.js

@@ -519,6 +519,8 @@ export default class Client extends EventTarget {
 		}
 
 		return new Promise((resolve, reject) => {
+			let removeEventListeners;
+
 			let handleMessage = (event) => {
 				let msg = event.detail.message;
 
@@ -531,18 +533,31 @@ export default class Client extends EventTarget {
 				try {
 					result = done(msg);
 				} catch (err) {
-					this.removeEventListener("message", handleMessage);
+					removeEventListeners();
 					reject(err);
 				}
 				if (result) {
-					this.removeEventListener("message", handleMessage);
+					removeEventListeners();
 					resolve(result);
 				}
 
 				// TODO: handle end of labeled response somehow
 			};
 
+			let handleStatus = () => {
+				if (this.status === Client.Status.DISCONNECTED) {
+					removeEventListeners();
+					reject(new Error("Connection closed"));
+				}
+			};
+
+			removeEventListeners = () => {
+				this.removeEventListener("message", handleMessage);
+				this.removeEventListener("status", handleStatus);
+			};
+
 			this.addEventListener("message", handleMessage);
+			this.addEventListener("status", handleStatus);
 			this.send(msg);
 		});
 	}