paths.js

const path = require('path')
const fs = require('fs')
const url = require('url')
const findMonorepo = require('react-dev-utils/workspaceUtils').findMonorepo

// Make sure any symlinks in the project folder are resolved:
// https://github.com/facebook/create-react-app/issues/637
const appDirectory = fs.realpathSync(process.cwd())
const resolveApp = relativePath => path.resolve(appDirectory, relativePath)

const envPublicUrl = process.env.PUBLIC_URL

function ensureSlash (inputPath, needsSlash) {
  const hasSlash = inputPath.endsWith('/')
  if (hasSlash && !needsSlash) {
    return inputPath.substr(0, inputPath.length - 1)
  } else if (!hasSlash && needsSlash) {
    return `${inputPath}/`
  } else {
    return inputPath
  }
}

const getPublicUrl = appPackageJson =>
  envPublicUrl || require(appPackageJson).homepage

// We use `PUBLIC_URL` environment variable or "homepage" field to infer
// "public path" at which the app is served.
// Webpack needs to know it to put the right <script> hrefs into HTML even in
// single-page apps that may serve index.html for nested URLs like /todos/42.
// We can't use a relative path in HTML because we don't want to load something
// like /todos/42/static/js/bundle.7289d.js. We have to know the root.
function getServedPath (appPackageJson) {
  const publicUrl = getPublicUrl(appPackageJson)
  const servedUrl =
    envPublicUrl || (publicUrl ? url.parse(publicUrl).pathname : '/')
  return ensureSlash(servedUrl, true)
}

// config after eject: we're in ./config/
module.exports = {
  dotenv: resolveApp('.env'),
  appPath: resolveApp('.'),
  appBuild: resolveApp('build'),
  appPublic: resolveApp('public'),
  appHtml: resolveApp('public/index.html'),
  appIndexJs: resolveApp('../common/index.js'),
  appPackageJson: resolveApp('package.json'),
  appSrc: resolveApp('../.'),
  testsSetup: resolveApp('src/setupTests.js'),
  appNodeModules: resolveApp('node_modules'),
  publicUrl: getPublicUrl(resolveApp('package.json')),
  servedPath: getServedPath(resolveApp('package.json'))
}

let checkForMonorepo = true

module.exports.srcPaths = [module.exports.appSrc + '/common']

module.exports.useYarn = fs.existsSync(
  path.join(module.exports.appPath, 'yarn.lock')
)

if (checkForMonorepo) {
  // if app is in a monorepo (lerna or yarn workspace), treat other packages in
  // the monorepo as if they are app source
  const mono = findMonorepo(appDirectory)
  if (mono.isAppIncluded) {
    Array.prototype.push.apply(module.exports.srcPaths, mono.pkgs)
  }
  module.exports.useYarn = module.exports.useYarn || mono.isYarnWs
}