storybook/lib/builder-webpack5/src/presets/preview-preset.ts

import webpackConfig from '../preview/iframe-webpack.config';

export const webpack = async (_: unknown, options: any) => webpackConfig(options);

export const entries = async (_: unknown, options: any) => {
  let result: string[] = [];

  result = result.concat(await options.presets.apply('previewEntries', [], options));

  if (options.configType === 'DEVELOPMENT') {
    // Suppress informational messages when --quiet is specified. webpack-hot-middleware's quiet
    // parameter would also suppress warnings.
    result = result.concat(
      `${require.resolve('webpack-hot-middleware/client')}?reload=true&quiet=false&noInfo=${
        options.quiet
      }`
    );
  }

  return result;
};

export const babel = async (config: any, options: any) => ({
  ...config,
  overrides: [
    ...(config?.overrides || []),
    {
      test: /\.(story|stories).*$/,
      plugins: [require.resolve('babel-plugin-named-exports-order')],
    },
  ],
});