Dispose of attach addon event listeners

src/addons/attach/Interfaces.ts

@@ -5,9 +5,13 @@
  * Implements the attach method, that attaches the terminal to a WebSocket stream.
  */
 
-import { Terminal } from 'xterm';
+import { Terminal, IDisposable } from 'xterm';
 
 export interface IAttachAddonTerminal extends Terminal {
+  _core: {
+    register<T extends IDisposable>(d: T): void;
+  };
+
   __socket?: WebSocket;
   __attachSocketBuffer?: string;
 

src/addons/attach/attach.ts

@@ -5,7 +5,7 @@
  * Implements the attach method, that attaches the terminal to a WebSocket stream.
  */
 
-import { Terminal } from 'xterm';
+import { Terminal, IDisposable } from 'xterm';
 import { IAttachAddonTerminal } from './Interfaces';
 
 /**
@@ -87,14 +87,28 @@ export function attach(term: Terminal, socket: WebSocket, bidirectional: boolean
     socket.send(data);
   };
 
-  socket.addEventListener('message', addonTerminal.__getMessage);
+  addonTerminal._core.register(addSocketListener(socket, 'message', addonTerminal.__getMessage));
 
   if (bidirectional) {
     addonTerminal.on('data', addonTerminal.__sendData);
   }
 
-  socket.addEventListener('close', () => detach(addonTerminal, socket));
-  socket.addEventListener('error', () => detach(addonTerminal, socket));
+  addonTerminal._core.register(addSocketListener(socket, 'close', () => detach(addonTerminal, socket)));
+  addonTerminal._core.register(addSocketListener(socket, 'error', () => detach(addonTerminal, socket)));
+}
+
+function addSocketListener(socket: WebSocket, type: string, handler: (this: WebSocket, ev: Event) => any): IDisposable {
+  socket.addEventListener(type, handler);
+  return {
+    dispose: () => {
+      if (!handler) {
+        // Already disposed
+        return;
+      }
+      socket.removeEventListener(type, handler);
+      handler = null;
+    }
+  };
 }
 
 /**