babel.config.js

const path = require('path');

function resolveAliasPath(relativeToBabelConf) {
  const resolvedPath = path.relative(process.cwd(), path.resolve(__dirname, relativeToBabelConf));
  return `./${resolvedPath.replace('\\', '/')}`;
}

module.exports = function getBabelConfig(api) {
  const useESModules = api.env(['regressions', 'legacy', 'modern', 'stable', 'rollup']);

  const defaultAlias = {
    '@pigment-css/react': resolveAliasPath('./packages/pigment-css-react/src'),
  };

  const presets = [
    [
      '@babel/preset-env',
      {
        bugfixes: true,
        browserslistEnv: process.env.BABEL_ENV || process.env.NODE_ENV,
        debug: process.env.MUI_BUILD_VERBOSE === 'true',
        modules: useESModules ? false : 'commonjs',
        shippedProposals: api.env('modern'),
      },
    ],
    [
      '@babel/preset-react',
      {
        runtime: 'automatic',
      },
    ],
    '@babel/preset-typescript',
  ];

  const plugins = [];

  if (process.env.NODE_ENV === 'test') {
    plugins.push([
      'babel-plugin-module-resolver',
      {
        alias: defaultAlias,
        root: ['./'],
      },
    ]);
  }

  return {
    assumptions: {
      noDocumentAll: true,
    },
    presets,
    plugins,
    ignore: [/@babel[\\|/]runtime/], // Fix a Windows issue.
    overrides: [
      {
        exclude: /\.test\.(js|ts|tsx)$/,
        plugins: ['@babel/plugin-transform-react-constant-elements'],
      },
    ],
    env: {
      coverage: {
        plugins: [
          'babel-plugin-istanbul',
          [
            'babel-plugin-module-resolver',
            {
              root: ['./'],
              alias: defaultAlias,
            },
          ],
        ],
      },
      development: {
        plugins: [
          [
            'babel-plugin-module-resolver',
            {
              alias: {
                ...defaultAlias,
                modules: './modules',
              },
              root: ['./'],
            },
          ],
        ],
      },
      rollup: {
        plugins: [
          [
            'babel-plugin-module-resolver',
            {
              alias: defaultAlias,
            },
          ],
        ],
      },
      test: {
        sourceMaps: 'both',
        plugins: [
          [
            'babel-plugin-module-resolver',
            {
              root: ['./'],
              alias: defaultAlias,
            },
          ],
        ],
      },
      benchmark: {
        plugins: [
          [
            'babel-plugin-module-resolver',
            {
              alias: defaultAlias,
            },
          ],
        ],
      },
    },
  };
};