https://github.com/facebook/stylex/pull/781#discussion_r1857173353

postcss.config.js

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 *
 */

const fs = require('fs');
const path = require('path');

function getPackageExports(packageName) {
  const packageJsonPath = require.resolve(`${packageName}/package.json`);
  const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8'));

  if (packageJson.exports) {
    const exports = {};
    for (const key in packageJson.exports) {
      if (typeof packageJson.exports[key] === 'string') {
        exports[key] = require.resolve(
          path.join(packageName, packageJson.exports[key]),
        );
      } else if (typeof packageJson.exports[key] === 'object') {
        exports[key] = getPackageExports(path.join(packageName, key));
      }
    }
    return exports;
  } else {
    return require.resolve(packageName);
  }
}

module.exports = {
  plugins: {
    '@stylexjs/postcss-plugin': {
      include: [
        'app/**/*.{js,jsx,ts,tsx}',
        'components/**/*.{js,jsx,ts,tsx}',
        getPackageExports('@stylexjs/open-props'),
      ],
      useCSSLayers: true,
    },
    autoprefixer: {},
  },
};