EntityRouteProviderSubscriber.php

<?php

namespace Drupal\Core\EventSubscriber;

use Drupal\Core\Entity\EntityTypeManagerInterface;
use Drupal\Core\Routing\RouteBuildEvent;
use Drupal\Core\Routing\RoutingEvents;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\Routing\RouteCollection;

/**
 * Ensures that routes can be provided by entity types.
 */
class EntityRouteProviderSubscriber implements EventSubscriberInterface {
    
    /**
     * The entity type manager service.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * Constructs a new EntityRouteProviderSubscriber instance.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager service.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager) {
        $this->entityTypeManager = $entity_type_manager;
    }
    
    /**
     * Provides routes on route rebuild time.
     *
     * @param \Drupal\Core\Routing\RouteBuildEvent $event
     *   The route build event.
     */
    public function onDynamicRouteEvent(RouteBuildEvent $event) {
        $route_collection = $event->getRouteCollection();
        foreach ($this->entityTypeManager
            ->getDefinitions() as $entity_type) {
            if ($entity_type->hasRouteProviders()) {
                foreach ($this->entityTypeManager
                    ->getRouteProviders($entity_type->id()) as $route_provider) {
                    // Allow to both return an array of routes or a route collection,
                    // like route_callbacks in the routing.yml file.
                    $routes = $route_provider->getRoutes($entity_type);
                    if ($routes instanceof RouteCollection) {
                        $routes = $routes->all();
                    }
                    foreach ($routes as $route_name => $route) {
                        // Don't override existing routes.
                        if (!$route_collection->get($route_name)) {
                            $route_collection->add($route_name, $route);
                        }
                    }
                }
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        $events[RoutingEvents::DYNAMIC][] = [
            'onDynamicRouteEvent',
        ];
        return $events;
    }

}