Why overwrites query by handshake?

[imcuttle]

When I use socket.io multiplexing feat, setup ws connection by query {type: ''}, and then I updated query {type: 'share'}, but it not received in server side, I saw code as follow

socket.io/lib/socket.js

Lines 116 to 120 in 2a1aa1c

	function buildQuery(){
	var requestQuery = url.parse(self.request.url, true).query;
	//if socket-specific query exist, replace query strings in requestQuery
	return Object.assign({}, query, requestQuery);
	}

So why overwrites query by handshake? And now I use forceNew=true to disable multiplexing feat

[sebamarynissen]

It's a bug that I've encountered as well. I still need to test if it's fixed in v3, but have a look at #3495 for a workaround in v2.

[darrachequesne]

Yes, that's a known quirk in Socket.IO v2, which should be fixed in v3. The explanation can be found in the migration guide: https://socket.io/docs/migrating-from-2-x-to-3-0/#Add-a-clear-distinction-between-the-Manager-query-option-and-the-Socket-query-option

As a workaround for Socket.IO v2, you can explicitly create your Socket instance on the client-side.

Instead of:

const socket = io({
  query: {
     token: "abc"
  }
});

You can write:

const { Manager } = require("socket.io-client");

const manager = new Manager();

const socket = manager.socket("/", {
  query: {
    token: "abc"
  }
});

In this case, you can update the socket.query object, it should be reflected on the server-side upon reconnection (and not overriden by the Manager query option):

// client-side
socket.query.token = "def";

// server-side
io.on("connect", (socket) => {
  console.log(socket.handshake.query.token); // def
});

[sebamarynissen]

@darrachequesne Would there be a possibility to merge #3496 into the 2.4.x branch? It looks to me that the problem is simply that the http query overrides the socket specific query, while the socket specific query should actually override the http query instead (see #3495 (comment)).