Change the "add entity" page title on a custom content entity type using alterRoutes()?

Question

I created a custom content entity type dog using drush generate entity:content.

When I go to www.example.com/dog/add, the page title (the one in the <title> tag, not the <h1> tag) is "Add dog". I want to change this to "Send a dog to outer space (and bring him back safely)".

It seems there is no place to set the title in the entity annotations, so I attempted to add an event subscriber:

dog/src/Routing/DogRouteSubscriber.php

class DogRouteSubscriber extends RouteSubscriberBase {

  /**
   * {@inheritdoc}
   */
  protected function alterRoutes(RouteCollection $collection) {
    if ($route = $collection->get('entity.dog.add_form')) {
      $route->setDefault('_title', 'Send a dog to outer space (and bring him back safely)');
    }
  }
}

dog.services.yml

services:
  dog.route_subscriber:
    class: Drupal\dog\Routing\DogRouteSubscriber
    tags:
      - { name: event_subscriber }

I am using $route->setDefault('_title', 'Send a dog to outer space (and bring him back safely)' based on code in this blog post, but even after rebuilding the cache, the page title isn't changed.

So: Where do I alter (or set) the entity add form's page title?

Similar but different questions:

• How can I change the page title? (general question about page titles)
• How can I change the title of the node/add page of a specific content type? (question about node content types, not custom entity types in general)

Answer 1

If your entity uses DefaultHtmlRouteProvider as route_provider handler then it sets a title callback which has a higher priority than the static title. So you would need to remove this default in alterRoutes().

However, if this is your own entity, a more straightforward approach would be to edit the entity annotations and replace the route_provider handler with your own class , which extends DefaultHtmlRouteProvider and overrides the method getAddPageRoute():

  protected function getAddPageRoute(EntityTypeInterface $entity_type) {
    if ($entity_type->hasLinkTemplate('add-page') && $entity_type->getKey('bundle')) {
      $route = new Route($entity_type->getLinkTemplate('add-page'));
      $route->setDefault('_controller', EntityController::class . '::addPage');
      $route->setDefault('_title_callback', EntityController::class . '::addTitle');
      $route->setDefault('entity_type_id', $entity_type->id());
      $route->setRequirement('_entity_create_any_access', $entity_type->id());

      return $route;
    }
  }

Or keep the dynamic controller method and return the static text from there.

Answer 2

Wow, this turned out to be way more complex than I thought.

In addition to the DogRouteSubscriber shown in the original question, I had to override getAddFormRoute (because the basic entity type generated with drush generate does not have an add-page route) with my own DogHtmlRouteProvider class (as described in 4uk4's answer):

class DogHtmlRouteProvider extends DefaultHtmlRouteProvider {

  /**
   * Gets the add-form route.
   *
   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
   *   The entity type.
   *
   * @return \Symfony\Component\Routing\Route|null
   *   The generated route, if available.
   */
  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,
      ]);

      $route
        ->setRequirement('_entity_create_access', $entity_type_id);

      return $route;
    }
  }

Here, I removed the line $route->setDefault('_title_callback', EntityController::class . '::addTitle'); I did not override this with another method because _title_callback apparently only accepts a method on a descendant of EntityController, and my module doesn't have such a controller.