msw/cli/init.js

const fs = require('fs')
const path = require('path')
const chalk = require('chalk')
const inquirer = require('inquirer')
const invariant = require('./invariant')
const { SERVICE_WORKER_BUILD_PATH } = require('../config/constants')

const CWD = process.cwd()

module.exports = function init(args) {
  const { publicDir, save } = args

  // When running as a part of "postinstall" script, "cwd" equals the library's directory.
  // The "postinstall" script resolves the right absolute public directory path.
  const absolutePublicDir = path.isAbsolute(publicDir)
    ? publicDir
    : path.resolve(CWD, publicDir)
  const relativePublicDir = path.relative(CWD, absolutePublicDir)
  const dirExists = fs.existsSync(absolutePublicDir)

  invariant(
    dirExists,
    'Failed to create a Service Worker at "%s": directory does not exist.\nMake sure to include a relative path to the root directory of your server.',
    absolutePublicDir,
  )

  console.log(
    'Initializing the Mock Service Worker at "%s"...',
    absolutePublicDir,
  )

  const serviceWorkerFilename = path.basename(SERVICE_WORKER_BUILD_PATH)
  const swDestFilepath = path.resolve(absolutePublicDir, serviceWorkerFilename)

  fs.copyFileSync(SERVICE_WORKER_BUILD_PATH, swDestFilepath)

  console.log(`
${chalk.green('Service Worker successfully created!')}
${chalk.gray(swDestFilepath)}

Continue by creating a mocking definition module in your application:

${chalk.cyan.bold('https://mswjs.io/docs/getting-started/mocks')}
`)

  const packageJsonPath = path.resolve(CWD, 'package.json')
  const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8'))
  const { msw: mswConfig } = packageJson

  if (mswConfig && mswConfig.workerDirectory === relativePublicDir) {
    return
  }

  // When called `msw init --no-save` do not show the save suggestions.
  if (save === false) {
    return
  }

  if (!mswConfig) {
    console.log(`\
${chalk.cyan('INFO')} In order to ease the future updates to the worker script,
we recommend saving the path to the worker directory in your package.json.
        `)

    if (save) {
      return saveWorkerDirectory(packageJsonPath, relativePublicDir)
    }

    return promptWorkerDirectoryUpdate(
      `Do you wish to save "${relativePublicDir}" as the worker directory?`,
      packageJsonPath,
      relativePublicDir,
    )
  }

  if (mswConfig.workerDirectory !== relativePublicDir) {
    console.log(
      `\
${chalk.yellowBright(
  'WARN',
)} The "msw.workerDirectory" in your package.json ("%s")
is different from the worker directory used right now ("%s").
    `,
      mswConfig.workerDirectory,
      relativePublicDir,
    )

    if (save) {
      return saveWorkerDirectory(packageJsonPath, relativePublicDir)
    }

    return promptWorkerDirectoryUpdate(
      `Do you wish to use "${relativePublicDir}" instead of "${mswConfig.workerDirectory}" as the worker directory?`,
      packageJsonPath,
      relativePublicDir,
    )
  }
}

function saveWorkerDirectory(packageJsonPath, publicDir) {
  const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8'))

  console.log(
    chalk.gray('Writing "msw.workerDirectory" to "%s"...'),
    packageJsonPath,
  )

  const nextPackageJson = Object.assign({}, packageJson, {
    msw: {
      workerDirectory: publicDir,
    },
  })

  fs.writeFileSync(
    packageJsonPath,
    JSON.stringify(nextPackageJson, null, 2),
    'utf8',
  )
}

function promptWorkerDirectoryUpdate(message, packageJsonPath, publicDir) {
  return inquirer
    .prompt({
      type: 'confirm',
      name: 'saveWorkerDirectory',
      prefix: chalk.yellowBright('?'),
      message,
    })
    .then((answers) => {
      if (!answers.saveWorkerDirectory) {
        return
      }

      saveWorkerDirectory(packageJsonPath, publicDir)
    })
}