refactor: remove the wsPreEncoded option

The wsPreEncoded option was added in the `socket.io-adapter` package
when broadcasting a message to multiple clients.

It was removed in [1] and is now superseded by the `wsPreEncodedFrame`
option, which directly computes the WebSocket frame once for all
clients (see [2]).

[1]: socketio/socket.io-adapter@88eee59
[2]: socketio/socket.io-adapter@5f7b47d

lib/transports/websocket.ts

@@ -85,9 +85,7 @@ export class WebSocket extends Transport {
         this.socket.send(data, opts, onSent);
       };
 
-      if (packet.options && typeof packet.options.wsPreEncoded === "string") {
-        send(packet.options.wsPreEncoded);
-      } else if (this._canSendPreEncodedFrame(packet)) {
+      if (this._canSendPreEncodedFrame(packet)) {
         // the WebSocket frame was computed with WebSocket.Sender.frame()
         // see https://github.com/websockets/ws/issues/617#issuecomment-283002469
         this.socket._sender.sendFrame(packet.options.wsPreEncodedFrame, onSent);

test/server.js

@@ -2889,25 +2889,6 @@ describe("server", () => {
     });
 
     describe("pre-encoded content", () => {
-      it("should use the pre-encoded content", (done) => {
-        engine = listen((port) => {
-          client = new ClientSocket(`ws://localhost:${port}`, {
-            transports: ["websocket"],
-          });
-
-          engine.on("connection", (conn) => {
-            conn.send("test", {
-              wsPreEncoded: "4test pre-encoded",
-            });
-          });
-
-          client.on("message", (msg) => {
-            expect(msg).to.be("test pre-encoded");
-            done();
-          });
-        });
-      });
-
       it("should use the pre-encoded frame", function (done) {
         if (process.env.EIO_WS_ENGINE === "uws") {
           return this.skip();