index.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */
'use strict';

var path = require('path');

module.exports = {
  presets: [
    // Latest stable ECMAScript features
    require.resolve('babel-preset-latest'),
    // JSX, Flow
    require.resolve('babel-preset-react')
  ],
  plugins: [
    // class { handleClick = () => { } }
    require.resolve('babel-plugin-transform-class-properties'),
    // { ...todo, completed: true }
    require.resolve('babel-plugin-transform-object-rest-spread'),
    // function* () { yield 42; yield 43; }
    [require.resolve('babel-plugin-transform-regenerator'), {
      // Async functions are converted to generators by babel-preset-latest
      async: false
    }],
    // Polyfills the runtime needed for async/await and generators
    [require.resolve('babel-plugin-transform-runtime'), {
      helpers: false,
      polyfill: false,
      regenerator: true,
      // Resolve the Babel runtime relative to the config.
      moduleName: path.dirname(require.resolve('babel-runtime/package'))
    }]
  ]
};

// This is similar to how `env` works in Babel:
// https://babeljs.io/docs/usage/babelrc/#env-option
// We are not using `env` because it’s ignored in versions > babel-core@6.10.4:
// https://github.com/babel/babel/issues/4539
// https://github.com/facebookincubator/create-react-app/issues/720
// It’s also nice that we can enforce `NODE_ENV` being specified.
var env = process.env.BABEL_ENV || process.env.NODE_ENV;
if (env !== 'development' && env !== 'test' && env !== 'production') {
  throw new Error(
    'Using `babel-preset-react-app` requires that you specify `NODE_ENV` or '+
    '`BABEL_ENV` environment variables. Valid values are "development", ' +
    '"test", and "production". Instead, received: ' + JSON.stringify(env) + '.'
  );
}
var plugins = module.exports.plugins;
if (env === 'development' || env === 'test') {
  plugins.push.apply(plugins, [
    // Adds component stack to warning messages
    require.resolve('babel-plugin-transform-react-jsx-source'),
    // Adds __self attribute to JSX which React will use for some warnings
    require.resolve('babel-plugin-transform-react-jsx-self')
  ]);
}
if (env === 'production') {
  // Optimization: hoist JSX that never changes out of render()
  // Disabled because of issues:
  // * https://github.com/facebookincubator/create-react-app/issues/525
  // * https://phabricator.babeljs.io/search/query/pCNlnC2xzwzx/
  // * https://github.com/babel/babel/issues/4516
  // TODO: Enable again when these issues are resolved.
  // plugins.push.apply(plugins, [
  //   require.resolve('babel-plugin-transform-react-constant-elements')
  // ]);
}