How to use the @rails/webpacker.config.publicPath function in @rails/webpacker

serverWebpackConfig.optimization = {
    minimize: false
  }
  serverWebpackConfig.plugins.unshift(
    new webpack.optimize.LimitChunkCountPlugin({ maxChunks: 1 })
  )

  // Custom output for the server-bundle that matches the config in
  // config/initializers/react_on_rails.rb
  serverWebpackConfig.output = {
    filename: 'server-bundle.js',
    globalObject: 'this',
    // If using the React on Rails Pro node server renderer, uncomment the next line
    // libraryTarget: 'commonjs2',
    path: config.outputPath,
    publicPath: config.publicPath,
    // https://webpack.js.org/configuration/output/#outputglobalobject
  }

  // Don't hash the server bundle b/c would conflict with the client manifest
  // And no need for the MiniCssExtractPlugin
  serverWebpackConfig.plugins = serverWebpackConfig.plugins.filter(
    (plugin) =>
      plugin.constructor.name !== 'WebpackAssetsManifest' &&
      plugin.constructor.name !== 'MiniCssExtractPlugin' &&
      plugin.constructor.name !== 'ForkTsCheckerWebpackPlugin'
  )

  // Configure loader rules for SSR
  // Remove the mini-css-extract-plugin from the style loaders because
  // the client build will handle exporting CSS.
  // replace file-loader with null-loader