netlify-cli/src/detectors/parcel.js

const { hasRequiredDeps, hasRequiredFiles, getYarnOrNPMCommand, scanScripts } = require('./utils/jsdetect')

module.exports = function() {
  /* REQUIRED FILES */
  if (!hasRequiredFiles(['package.json'])) return false

  /* REQUIRED DEPS */
  if (!(hasRequiredDeps(['parcel-bundler']) || hasRequiredDeps(['parcel']))) return false

  /* Everything below now assumes that we are within parcel */

  const possibleArgsArrs = scanScripts({
    preferredScriptsArr: ['start', 'dev', 'run'],
    preferredCommand: 'parcel'
  })

  if (possibleArgsArrs.length === 0) {
    /* Offer to run it when the user doesnt have any scripts setup! 🤯 */
    possibleArgsArrs.push(['parcel'])
  }

  return {
    type: 'parcel',
    command: getYarnOrNPMCommand(),
    port: 8888,
    proxyPort: 1234,
    env: { ...process.env },
    possibleArgsArrs,
    urlRegexp: new RegExp(`(http://)([^:]+:)${1234}(/)?`, 'g'),
    dist: 'dist'
  }
}