EntityRevisionRouteEnhancer.php

<?php

namespace Drupal\Core\Routing\Enhancer;

use Drupal\Core\Routing\EnhancerInterface;
use Symfony\Cmf\Component\Routing\RouteObjectInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Routing\Route;

/**
 * Adds _entity_revision to the request attributes, if possible.
 */
class EntityRevisionRouteEnhancer implements EnhancerInterface {
    
    /**
     * Returns whether the enhancer runs on the current route.
     *
     * @param \Symfony\Component\Routing\Route $route
     *   The current route.
     *
     * @return bool
     */
    protected function applies(Route $route) {
        // Check whether there is any entity revision parameter.
        $parameters = $route->getOption('parameters') ?: [];
        foreach ($parameters as $info) {
            if (isset($info['type']) && strpos($info['type'], 'entity_revision:') === 0) {
                return TRUE;
            }
        }
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function enhance(array $defaults, Request $request) {
        
        /** @var \Symfony\Component\Routing\Route $route */
        $route = $defaults[RouteObjectInterface::ROUTE_OBJECT];
        if (!$this->applies($route)) {
            return $defaults;
        }
        $options = $route->getOptions();
        if (isset($options['parameters'])) {
            foreach ($options['parameters'] as $name => $details) {
                if (!empty($details['type']) && strpos($details['type'], 'entity_revision:') !== FALSE) {
                    $defaults['_entity_revision'] = $defaults[$name];
                    break;
                }
            }
        }
        return $defaults;
    }

}