CssAssetController.php

<?php

namespace Drupal\system\Controller;

use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\HttpFoundation\Request;
use Drupal\Core\Asset\AttachedAssetsInterface;
use Drupal\Core\Asset\AssetGroupSetHashTrait;

/**
 * Defines a controller to serve CSS aggregates.
 */
class CssAssetController extends AssetControllerBase {
  use AssetGroupSetHashTrait;
  
  /**
   * {@inheritdoc}
   */
  protected string $contentType = 'text/css';
  
  /**
   * {@inheritdoc}
   */
  protected string $assetType = 'css';
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('stream_wrapper_manager'), $container->get('library.dependency_resolver'), $container->get('asset.resolver'), $container->get('theme.initialization'), $container->get('theme.manager'), $container->get('asset.css.collection_grouper'), $container->get('asset.css.collection_optimizer'), $container->get('asset.css.dumper'));
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getGroups(AttachedAssetsInterface $attached_assets, Request $request) : array {
    $language = $this->languageManager()
      ->getLanguage($request->get('language'));
    $assets = $this->assetResolver
      ->getCssAssets($attached_assets, FALSE, $language);
    return $this->grouper
      ->group($assets);
  }

}