index.js

/**
 * Babel webpack block.
 *
 * @see https://github.com/babel/babel-loader
 */

module.exports = babel

/**
 * @param {object} [options]
 * @param {bool}                    [options.cacheDirectory]  Use cache directory. Defaults to true.
 * @param {string[]}                [options.plugins]         Babel plugins to use.
 * @param {string[]}                [options.presets]         Babel presets to use.
 * @return {Function}
 */
function babel(options = {}) {
  options = Object.assign(
    {
      cacheDirectory: true
    },
    options
  )

  const setter = context => prevConfig => {
    context.babel = context.babel || {}

    // Merge babel config into the one stored in context
    context.babel = Object.assign(
      {},
      context.babel,
      options,
      options.plugins ? { plugins: (context.babel.plugins || []).concat(options.plugins) } : {},
      options.presets ? { presets: (context.babel.presets || []).concat(options.presets) } : {}
    )
    return prevConfig
  }

  return Object.assign(setter, { post: postConfig })
}

function postConfig(context, util) {
  const ruleConfig = Object.assign(
    {
      test: /\.(js|jsx)$/,
      exclude: /node_modules/,
      use: [{ loader: 'babel-loader', options: context.babel }]
    },
    context.match
  )

  return util.addLoader(ruleConfig)
}