next.js/bin/next-dev

#!/usr/bin/env node
import 'source-map-support/register'
import { resolve, join } from 'path'
import parseArgs from 'minimist'
import { existsSync, readFileSync } from 'fs'
import Server from '../server'
import { printAndExit } from '../lib/utils'
import pkgUp from 'pkg-up'

process.env.NODE_ENV = process.env.NODE_ENV || 'development'

const argv = parseArgs(process.argv.slice(2), {
  alias: {
    h: 'help',
    p: 'port'
  },
  boolean: ['h'],
  default: {
    p: 3000
  }
})

if (argv.help) {
  console.log(`
    Description
      Starts the application in development mode (hot-code reloading, error
      reporting, etc)

    Usage
      $ next dev <dir> -p <port number>

    <dir> represents where the compiled .next folder should go.
    If no directory is provided, .next will be created in the current directory

    Options
      --port, -p      A port number on which to start the application
      --help, -h      Displays this message
  `)
  process.exit(0)
}

const dir = resolve(argv._[0] || '.')

// Check if pages dir exists and warn if not
if (!existsSync(dir)) {
  printAndExit(`> No such directory exists as the project root: ${dir}`)
}

if (!existsSync(join(dir, 'pages'))) {
  if (existsSync(join(dir, '..', 'pages'))) {
    printAndExit('> No `pages` directory found. Did you mean to run `next` in the parent (`../`) directory?')
  }

  printAndExit('> Couldn\'t find a `pages` directory. Please create one under the project root')
}

const srv = new Server({ dir, dev: true })
srv.start(argv.port)
.then(async () => {
  if (!process.env.NOW) {
    console.log(`> Ready on http://localhost:${argv.port}`)
  }
})
.catch((err) => {
  if (err.code === 'EADDRINUSE') {
    let errorMessage = `Port ${argv.port} is already in use.`
    const pkgAppPath = pkgUp.sync('.')
    const appPackage = JSON.parse(readFileSync(pkgAppPath, 'utf8'))
    const nextScript = Object.entries(appPackage.scripts).find(scriptLine => scriptLine[1] === 'next')
    if (nextScript) errorMessage += `\nUse \`npm run ${nextScript[0]} -- -p <some other port>\`.`
    console.error(errorMessage)
  } else {
    console.error(err)
  }
  process.nextTick(() => process.exit(1))
})