Function process

src/worker.js:41–178

({ file, source, map, options = {} })

 * @param {number} [$0.options.corejsVersion]
 */
export async function process ({ file, source, map, options = {} }) {
  const { timings, start, end } = options.timings ? createPerformanceTimings() : noopTimings;
  const { minify, downlevel, modernize } = options;

  const polyfills = new Set();
  let legacy;

  const outputOptions = {
    compact: minify,
    minified: minify,
    // envName: minify ? 'production' : 'development',
    comments: minify ? false : undefined,
    generatorOpts: {
      concise: true
    }
  };

  start('modern');
  const modern = await babel.transformAsync(source, {
    configFile: false,
    babelrc: false,
    filename: file,
    inputSourceMap: map,
    sourceMaps: true,
    sourceFileName: file,
    sourceType: 'module',
    envName: 'modern',
    // ast: true,
    presets: [
      ['@babel/preset-env', {
        loose: true,
        modules: false,
        bugfixes: true,
        targets: {
          esmodules: true
        },
        // corejs: options.corejsVersion,
        useBuiltIns: false
      }],
      modernize && ['babel-preset-modernize', {
        loose: true,
        webpack: true
      }]
    ].filter(Boolean),
    ...outputOptions,
    caller: {
      supportsStaticESM: true,
      name: NAME + '-modern'
    }
  });
  end('modern');

  if (minify) {
    start('modern-minify');
    const minified = await terser.minify(modern.code, {
      // Enables shorthand properties in objects and object patterns:
      ecma: 2017,
      module: false,