[feature] add a way to register middlewares for all namespaces

[darrachequesne]

Is your feature request related to a problem? Please describe.

Since Socket.IO v3, it is not mandatory anymore for the client to connect to the main namespace.

Registering a global middleware which applies to all namespace is thus a bit messier:

const of = io.of;
io.of = (...args) => {
  const nsp = of.call(io, ...args);
  nsp.use(yourMiddleware);
  return nsp;
}

Describe the solution you'd like

io.<name of the method>(yourMiddleware); // register a middleware which will be attached to each namespace

Describe alternatives you've considered

Registering a global middleware is possible for dynamic namespaces:

const parentNamespace = io.of(/^\/dynamic-\d+$/);

parentNamespace.use(yourMiddleware); // attached to all child namespaces

Additional context

Related: #3842

[stephaneeybert]

I also wanted to register a root main middlewaredid would fire up its handler for all namespaces.

I was trying to have the middleware:

io.use((socket, handler) => {
});

called up on a connection to:

server.io.of('/elearning').on('connection', function(socket) {
});

but the middleware handler would not fire up.

I also tried:

io.of('/').use((socket, handler) => {
});

but that also did not fire up.

Then I tried with a regex and that again did not fire up.

Only when I changed it to the same namespace is in the connection:

io.of('/elearning').use((socket, handler) => {
});

did it fire up.

But then I would need to have one same middleware for each and every namespace.

[sean256]

I'm glad I found this, I honestly thought io.use was bugged. v2 supported a global middleware and it was awesome.

[darrachequesne]

This was added in the documentation: https://socket.io/how-to/register-a-global-middleware

I'm not sure whether we should add some syntactic sugar over this, so I'm closing this. Please reopen if needed!