old_contents: let { resolve } = require('path')
  let chokidar = require('chokidar')
  let spinner = require('mico-spinner')
  
  let SizeLimitError = require('./size-limit-error')
  let createReporter = require('./create-reporter')
  let loadPlugins = require('./load-plugins')
  let createHelp = require('./create-help')
  let readPkgUp = require('./read-pkg-up')
  let getConfig = require('./get-config')
  let parseArgs = require('./parse-args')
  let debug = require('./debug')
  let calc = require('./calc')
  
  function throttle(fn) {
    let next, running
    // istanbul ignore next
    return () => {
      clearTimeout(next)
      next = setTimeout(async () => {
        await running
        running = fn()
      }, 200)
    }
  }
  
  async function findPlugins(parentPkg) {
    let plugins = loadPlugins(parentPkg)
  
    if (!parentPkg || !plugins.isEmpty) return plugins
  
    let cwd = resolve(parentPkg.path, '..', '..')
    let pkg = await readPkgUp(cwd)
  
    return findPlugins(pkg)
  }
  
  module.exports = async process => {
    function hasArg(arg) {
      return process.argv.includes(arg)
    }
    let isJsonOutput = hasArg('--json')
    let isSilentMode = hasArg('--silent')
    let reporter = createReporter(process, isJsonOutput, isSilentMode)
    let help = createHelp(process)
    let config, args
  
    try {
      if (hasArg('--version')) {
        return help.showVersion()
      }
  
      let pkg = await readPkgUp(process.cwd())
      let plugins = await findPlugins(pkg)
  
      if (hasArg('--help')) {
        return help.showHelp(plugins)
      }
  
      if (!pkg || !pkg.packageJson) {
        throw new SizeLimitError('noPackage')
      }
  
      args = parseArgs(plugins, process.argv)
  
      if (plugins.isEmpty) {
        help.showMigrationGuide(pkg)
        return process.exit(1)
      }
  
      config = await getConfig(plugins, process, args, pkg)
  
      let calcAndShow = async () => {
        let outputFunc = isJsonOutput ? null : spinner
        await calc(plugins, config, outputFunc)
        debug.results(process, args, config)
        reporter.results(plugins, config)
      }
  
      await calcAndShow()
  
      if (hasArg('--watch')) {
        let watcher = chokidar.watch(['**/*.js', 'package.json'], {
          ignored: '**/node_modules/**'
        })
        watcher.on('change', throttle(calcAndShow))
      }
  
      if ((config.failed || config.missed) && !args.why) process.exit(1)
    } catch (e) {
      debug.error(process, args, config)
      reporter.error(e)
      process.exit(1)
    }
  }
  
new_contents: let { resolve } = require('path')
  let chokidar = require('chokidar')
  let spinner = require('mico-spinner')
  
  let SizeLimitError = require('./size-limit-error')
  let createReporter = require('./create-reporter')
  let loadPlugins = require('./load-plugins')
  let createHelp = require('./create-help')
  let readPkgUp = require('./read-pkg-up')
  let getConfig = require('./get-config')
  let parseArgs = require('./parse-args')
  let debug = require('./debug')
  let calc = require('./calc')
  
  function throttle(fn) {
    let next, running
    // istanbul ignore next
    return () => {
      clearTimeout(next)
      next = setTimeout(async () => {
        await running
        running = fn()
      }, 200)
    }
  }
  
  async function findPlugins(parentPkg) {
    let plugins = loadPlugins(parentPkg)
  
    if (!parentPkg || !plugins.isEmpty) return plugins
  
    let cwd = resolve(parentPkg.path, '..', '..')
    let pkg = await readPkgUp(cwd)
  
    return findPlugins(pkg)
  }
  
  module.exports = async process => {
    function hasArg(arg) {
      return process.argv.includes(arg)
    }
    let isJsonOutput = hasArg('--json')
    let isSilentMode = hasArg('--silent')
    let reporter = createReporter(process, isJsonOutput, isSilentMode)
    let help = createHelp(process)
    let config, args
  
    try {
      if (hasArg('--version')) {
        return help.showVersion()
      }
  
      let pkg = await readPkgUp(process.cwd())
      let plugins = await findPlugins(pkg)
  
      if (hasArg('--help')) {
        return help.showHelp(plugins)
      }
  
      if (!pkg || !pkg.packageJson) {
        throw new SizeLimitError('noPackage')
      }
  
      args = parseArgs(plugins, process.argv)
  
      if (plugins.isEmpty) {
        help.showMigrationGuide(pkg)
        return process.exit(1)
      }
  
      config = await getConfig(plugins, process, args, pkg)
  
      let calcAndShow = async () => {
        let outputFunc = isJsonOutput ? null : spinner
        await calc(plugins, config, outputFunc)
        debug.results(process, args, config)
        reporter.results(plugins, config)
      }
  
      await calcAndShow()
  
      if (hasArg('--watch')) {
        let watcher = chokidar.watch(['**/*'], {
          ignored: '**/node_modules/**'
        })
        watcher.on('change', throttle(calcAndShow))
      }
  
      if ((config.failed || config.missed) && !args.why) process.exit(1)
    } catch (e) {
      debug.error(process, args, config)
      reporter.error(e)
      process.exit(1)
    }
  }
  
subject: Improve watch mode (#238)