DefaultHtmlRouteProvider::getAddFormRoute

protected DefaultHtmlRouteProvider::getAddFormRoute(EntityTypeInterface $entity_type)

protected function getAddFormRoute(EntityTypeInterface $entity_type) {
  if ($entity_type->hasLinkTemplate('add-form')) {
    $entity_type_id = $entity_type->id();
    $route = new Route($entity_type->getLinkTemplate('add-form'));
    // Use the add form handler, if available, otherwise default.
    $operation = 'default';
    if ($entity_type->getFormClass('add')) {
      $operation = 'add';
    }
    $route->setDefaults([
      '_entity_form' => "{$entity_type_id}.{$operation}",
      'entity_type_id' => $entity_type_id,
    ]);

    // If the entity has bundles, we can provide a bundle-specific title
    // and access requirements.
    $expected_parameter = $entity_type->getBundleEntityType() ? : $entity_type->getKey('bundle');
    // @todo: We have to check if a route contains a bundle in its path as
    //   test entities have inconsistent usage of "add-form" link templates.
    //   Fix it in https://www.drupal.org/node/2699959.
    if (($bundle_key = $entity_type->getKey('bundle')) && strpos($route->getPath(), '{' . $expected_parameter . '}') !== FALSE) {
      $route->setDefault('_title_callback', EntityController::class . '::addBundleTitle');
      // If the bundles are entities themselves, we can add parameter
      // information to the route options.
      if ($bundle_entity_type_id = $entity_type->getBundleEntityType()) {
        $bundle_entity_type = $this->entityTypeManager->getDefinition($bundle_entity_type_id);

        $route
        // The title callback uses the value of the bundle parameter to
        // fetch the respective bundle at runtime.
        ->setDefault('bundle_parameter', $bundle_entity_type_id)
          ->setRequirement('_entity_create_access', $entity_type_id . ':{' . $bundle_entity_type_id . '}');

        // Entity types with serial IDs can specify this in their route
        // requirements, improving the matching process.
        if ($this->getEntityTypeIdKeyType($bundle_entity_type) === 'integer') {
          $route->setRequirement($entity_type_id, '\d+');
        }

        $bundle_entity_parameter = ['type' => 'entity:' . $bundle_entity_type_id];
        if ($bundle_entity_type instanceof ConfigEntityTypeInterface) {
          // The add page might be displayed on an admin path. Even then, we
          // need to load configuration overrides so that, for example, the
          // bundle label gets translated correctly.
          // @see \Drupal\Core\ParamConverter\AdminPathConfigEntityConverter
          $bundle_entity_parameter['with_config_overrides'] = TRUE;
        }
        $route->setOption('parameters', [$bundle_entity_type_id => $bundle_entity_parameter]);
      }
      else {
        // If the bundles are not entities, the bundle key is used as the
        // route parameter name directly.
        $route
        ->setDefault('bundle_parameter', $bundle_key)
          ->setRequirement('_entity_create_access', $entity_type_id . ':{' . $bundle_key . '}');
      }
    }
    else {
      $route
      ->setDefault('_title_callback', EntityController::class . '::addTitle')
        ->setRequirement('_entity_create_access', $entity_type_id);
    }

    return $route;
  }
}