Fast404ExceptionHtmlSubscriber.php

<?php

namespace Drupal\Core\EventSubscriber;

use Drupal\Core\Config\ConfigFactoryInterface;
use Drupal\Component\Utility\Html;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
use Symfony\Component\HttpKernel\HttpKernelInterface;

/**
 * High-performance 404 exception subscriber.
 *
 * This subscriber will return a minimalist 404 response for HTML requests
 * without running a full page theming operation.
 */
class Fast404ExceptionHtmlSubscriber extends HttpExceptionSubscriberBase {
    
    /**
     * The HTTP kernel.
     *
     * @var \Symfony\Component\HttpKernel\HttpKernelInterface
     */
    protected $httpKernel;
    
    /**
     * The config factory.
     *
     * @var \Drupal\Core\Config\ConfigFactoryInterface
     */
    protected $configFactory;
    
    /**
     * Constructs a new Fast404ExceptionHtmlSubscriber.
     *
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   The configuration factory.
     * @param \Symfony\Component\HttpKernel\HttpKernelInterface $http_kernel
     *   The HTTP Kernel service.
     */
    public function __construct(ConfigFactoryInterface $config_factory, HttpKernelInterface $http_kernel) {
        $this->configFactory = $config_factory;
        $this->httpKernel = $http_kernel;
    }
    
    /**
     * {@inheritdoc}
     */
    protected static function getPriority() {
        // A very high priority so that it can take precedent over anything else,
        // and thus be fast.
        return 200;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getHandledFormats() {
        return [
            'html',
        ];
    }
    
    /**
     * Handles a 404 error for HTML.
     *
     * @param \Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent $event
     *   The event to process.
     */
    public function on404(GetResponseForExceptionEvent $event) {
        $request = $event->getRequest();
        $config = $this->configFactory
            ->get('system.performance');
        $exclude_paths = $config->get('fast_404.exclude_paths');
        if ($config->get('fast_404.enabled') && $exclude_paths && !preg_match($exclude_paths, $request->getPathInfo())) {
            $fast_paths = $config->get('fast_404.paths');
            if ($fast_paths && preg_match($fast_paths, $request->getPathInfo())) {
                $fast_404_html = strtr($config->get('fast_404.html'), [
                    '@path' => Html::escape($request->getUri()),
                ]);
                $response = new Response($fast_404_html, Response::HTTP_NOT_FOUND);
                $event->setResponse($response);
            }
        }
    }

}