fix: remove duplicate pipeline when serving bundle

Related: #4946

Author: darrachequesne

lib/index.ts

@@ -625,7 +625,6 @@ export class Server<
     switch (encoding) {
       case "br":
         res.writeHead(200, { "content-encoding": "br" });
-        readStream.pipe(createBrotliCompress()).pipe(res);
         pipeline(readStream, createBrotliCompress(), res, onError);
         break;
       case "gzip":

test/server-attachment.ts

@@ -70,6 +70,21 @@ describe("server attachment", () => {
         });
     });
 
+    it("should serve client (br)", (done) => {
+      const srv = createServer();
+      new Server(srv);
+      request(srv)
+        .get("/socket.io/socket.io.js")
+        .set("accept-encoding", "br")
+        .buffer(true)
+        .end((err, res) => {
+          if (err) return done(err);
+          expect(res.headers["content-encoding"]).to.be("br");
+          expect(res.status).to.be(200);
+          done();
+        });
+    });
+
     it("should serve client with necessary CORS headers", (done) => {
       const srv = createServer();
       new Server(srv, {