Listening for server-side next(err) middleware rejections

[nicholaswmin]

Hi again,

I'd like to access the nexted err I send back to the client in another middleware so I can log them.
I could obviously log before nexting, but I'd like to keep logging in one place, preferabbly a middleware.

The following would be ok:

// auth middleware
export default async (socket, next) => {
  const { err } = schema.validate(socket.handshake.auth)

  if (err)
    return next(err)
  
  // auth code continues..
}

Now, I have another middleware that logs stuff:

// logger middleware
export default (socket, next) => {
  // obv. this won't work, it's a client event
  socket.on('connect_error', err => {
    console.log(socket.data.id_user, 'rejected conn. reason:', err.message)
  })
  return next()
}

// main code
io.use(logger)
io.use(authenticator)

although I think an express-style error-handling middleware would be ideal.

io.use((err, socket, next) => {
  // by far the cleanest  :) 
  console.log(socket.data.id_user, 'rejected conn. reason:', err.message)
})