mastodon/babel.config.js

module.exports = function (api) {
  var validEnv = ['development', 'test', 'production'];
  var currentEnv = api.env();
  var isDevelopmentEnv = api.env('development');
  var isProductionEnv = api.env('production');
  var isTestEnv = api.env('test');

  if (!validEnv.includes(currentEnv)) {
    throw new Error(
      'Please specify a valid `NODE_ENV` or ' +
      '`BABEL_ENV` environment variables. Valid values are "development", ' +
      '"test", and "production". Instead, received: ' +
      JSON.stringify(currentEnv) +
      '.',
    );
  }

  return {
    presets: [
      isTestEnv && [
        '@babel/preset-env',
        {
          targets: {
            node: 'current',
          },
          modules: 'commonjs',
        },
        '@babel/preset-react',
      ],
      (isProductionEnv || isDevelopmentEnv) && [
        '@babel/preset-env',
        {
          forceAllTransforms: true,
          useBuiltIns       : 'entry',
          corejs            : 3,
          modules           : false,
          exclude           : ['transform-typeof-symbol'],
        },
      ],
      [
        '@babel/preset-react',
        {
          development: isDevelopmentEnv || isTestEnv,
          useBuiltIns: true,
        },
      ],
    ].filter(Boolean),
    plugins: [
      'babel-plugin-macros',
      '@babel/plugin-syntax-dynamic-import',
      isTestEnv && 'babel-plugin-dynamic-import-node',
      '@babel/plugin-transform-destructuring',
      [
        '@babel/plugin-proposal-decorators',
        { 'legacy': true },
      ],
      [
        '@babel/plugin-proposal-class-properties',
        {
          loose: true,
        },
      ],
      [
        '@babel/plugin-proposal-object-rest-spread',
        {
          useBuiltIns: true,
        },
      ],
      [
        '@babel/plugin-transform-runtime',
        {
          helpers    : false,
          regenerator: true,
          corejs     : false,
        },
      ],
      [
        '@babel/plugin-transform-regenerator',
        {
          async: false,
        },
      ],
      isProductionEnv && [
        'babel-plugin-transform-react-remove-prop-types',
        {
          removeImport: true,
        },
      ],
    ].filter(Boolean),
  };
};