@sap/cds-dk/lib/watch/open.js

Command line client and development toolkit for the SAP Cloud Application Programming Model

const childProcess = require('child_process')
const os = require('os')

module.exports.openURL = (urlArg, port) => {
  const url = _url(urlArg, port)
  return _open(url)
}

function _url (urlArg, port) {
  const base = `http://localhost:${port}/`
  if (typeof urlArg === 'string') {
    if (urlArg.startsWith('http'))  return urlArg
    return base + urlArg // partial URL
  }
  return base
}

function _open(args) {
  // http://stackoverflow.com/q/1480971/3191, but see below for Windows.
  let platform = process.platform

  // Attempt to detect Windows Subsystem for Linux (WSL). WSL  itself as Linux (which works in most cases), but in
  // this specific case we need to treat it as actually being Windows. The 'Windows-way' of opening things through
  // cmd.exe works just fine here, whereas using xdg-open does not, since there is no X Windows in WSL.
  if (platform === 'linux' && os.release().indexOf('Microsoft') !== -1) {
    platform = 'win32'
  }

  let command = process.env.BROWSER
  if (!command) {
    switch (platform) {
      case 'win32':  { command = 'cmd.exe';  break }
      case 'darwin': { command = 'open';     break }
      default:       { command = 'xdg-open'; break }
    }
  }

  if (typeof args === 'string')  args = [args]

  if (platform === 'win32') {
    // On Windows, we really want to use the 'start' command. But, the rules regarding arguments with spaces, and
    // escaping them with quotes, can get really arcane. So the easiest way to deal with this is to pass off the
    // responsibility to 'cmd /c', which has that logic built in.
    //
    // Furthermore, if 'cmd /c' double-quoted the first parameter, then 'start' will interpret it as a window title,
    // so we need to add a dummy empty-string window title: http://stackoverflow.com/a/154090/3191
    //
    // Additionally, on Windows ampersand and caret need to be escaped when passed to 'start'
    args = args.map(value => value.replace(/[&^]/g, '^$&'))
    args = ['/c', 'start'].concat(args)
  }

  const delay = parseInt(process.env.CDS_WATCH_OPEN_DELAY) || 1000
  setTimeout(() => {
    childProcess.execFile(command, args, null, err => {
      err && console.error(`Error opening '${command} ${args}' : ${err.message}`)
    })
  }, delay);
}