AssetRoutes.php

<?php

namespace Drupal\system\Routing;

use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
use Drupal\Core\StreamWrapper\StreamWrapperManagerInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\Routing\Route;

/**
 * Defines a routes' callback to register a URL for serving assets.
 */
class AssetRoutes implements ContainerInjectionInterface {
    
    /**
     * Constructs an asset routes object.
     *
     * @param \Drupal\Core\StreamWrapper\StreamWrapperManagerInterface $streamWrapperManager
     *   The stream wrapper manager service.
     */
    public function __construct(StreamWrapperManagerInterface $streamWrapperManager) {
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('stream_wrapper_manager'));
    }
    
    /**
     * Returns an array of route objects.
     *
     * @return \Symfony\Component\Routing\Route[]
     *   An array of route objects.
     */
    public function routes() : array {
        $routes = [];
        // Generate assets. If clean URLs are disabled image derivatives will always
        // be served through the routing system. If clean URLs are enabled and the
        // image derivative already exists, PHP will be bypassed.
        $directory_path = $this->streamWrapperManager
            ->getViaScheme('assets')
            ->getDirectoryPath();
        $routes['system.css_asset'] = new Route('/' . $directory_path . '/css/{file_name}', [
            '_controller' => 'Drupal\\system\\Controller\\CssAssetController::deliver',
        ], [
            '_access' => 'TRUE',
        ]);
        $routes['system.js_asset'] = new Route('/' . $directory_path . '/js/{file_name}', [
            '_controller' => 'Drupal\\system\\Controller\\JsAssetController::deliver',
        ], [
            '_access' => 'TRUE',
        ]);
        return $routes;
    }

}