Handle permessage-deflate on sockets

With this the extension host is working again.

src/node/routes/vscode.ts

@@ -207,5 +207,8 @@ wsRouter.ws("/", ensureAuthenticated, async (req) => {
       `Sec-WebSocket-Accept: ${reply}`,
     ].join("\r\n") + "\r\n\r\n",
   )
-  await vscode.sendWebsocket(req.ws, req.query)
+  // TODO: Parse this header properly. Currently unused so haven't bothered.
+  const extensions = req.headers["sec-websocket-extensions"]
+  const permessageDeflate = extensions ? extensions.includes("permessage-deflate") : false
+  await vscode.sendWebsocket(req.ws, req.query, permessageDeflate)
 })

src/node/vscode.ts

@@ -120,12 +120,12 @@ export class VscodeProvider {
   /**
    * VS Code expects a raw socket. It will handle all the web socket frames.
    */
-  public async sendWebsocket(socket: net.Socket, query: ipc.Query): Promise<void> {
+  public async sendWebsocket(socket: net.Socket, query: ipc.Query, permessageDeflate: boolean): Promise<void> {
     const vscode = await this._vscode
     // TLS sockets cannot be transferred to child processes so we need an
     // in-between. Non-TLS sockets will be returned as-is.
     const socketProxy = await this.socketProvider.createProxy(socket)
-    this.send({ type: "socket", query }, vscode, socketProxy)
+    this.send({ type: "socket", query, permessageDeflate }, vscode, socketProxy)
   }
 
   private send(message: ipc.CodeServerMessage, vscode?: cp.ChildProcess, socket?: net.Socket): void {