REPL net sockets should act like TTYs

[mranney]

It would be very useful if REPL net sockets could work like @TooTallNate ' s example:

https://gist.github.com/d9f15b31b60b09b84e54

So we could get readline functionality over REPL.

[TooTallNate]

It looks like the first step it to allow tty.ReadStream to accept a net.Socket instance so that you can retrieve "keypress" events properly.

Likely the inverse will be needed as well (passing a net.Socket to the tty.WriteStream constructor), but I haven't looked too deeply into that yet.

[TooTallNate]

I was able to get it working as expected with a lot of hacking:

// repl-server.js
var repl = require('repl')
var net = require('net')

// hack #1
process.stdin.resume()

net.createServer(function (socket) {

  // hack #2
  socket.isTTY = true

  // hack #3
  socket.getWindowSize = function () { return [ 80, 40 ] }

  // hack #4
  socket.cursorTo = require('tty').WriteStream.prototype.cursorTo
  socket.clearLine = require('tty').WriteStream.prototype.clearLine

  // hack #5
  socket._emitKey = require('tty').ReadStream.prototype._emitKey
  socket.on('data', function (b) {
    socket._emitKey(b)
  })

  var r = repl.start('socket repl > ', socket)

  // if REPLServer was an EE, and fired "exit", then this *would* work
  /*r.on('exit', function () {
    console.error('repl exit event, closing socket')
    socket.end()
  })*/
}).listen(1337)

// repl-client.js
var tty = require('tty')
var net = require('net')

var sock = net.createConnection(1337)

sock.on('connect', function () {
  process.stdin.resume();
  tty.setRawMode(true)
})

process.stdin.pipe(sock)
sock.pipe(process.stdout)

sock.on('end', function () {
  tty.setRawMode(false)
  process.stdin.pause()
})

Would have posted as a gist but github is erroring on me :(

[TooTallNate]

So we need to:

• Extend tty module to accept existing net.Socket instances. Currently it always creates a new instance.
• Remove existing "tty" semantics from "readline". Instead just turn this into an explicit "enabled" option/argument to readline.Interface.
• Move the "SIGWINCH" process handler from readline itself to somewhere else (or better detection for when process.stdin/stdout is being used)...
• Would also be nice to turn REPLServer into an EventEmitter, so that it can fire "exit" event and "error" events. Currently there's no way to really be sure when .exit was typed.

Comments?

[mranney]

This is great work, thanks. The value of a good interactive net REPL is perhaps hard to understand until you need to fix tricky problems in production.

[TooTallNate]

Fixed by #2922 :)