Can routing use parameters already in the URL?

Question

I'm actually using D9 to build a system with entities using sub-entities. The main entity system use the following path : /item/{item} Each sub entity is related to a main entity and use this path : /item/{item}/sub_item/{sub_item}

So to access the edit or delete form, the following pathes are required :

/item/{item}/sub_item/{sub_item}/edit /item/{item}/sub_item/{sub_item}/delete

For example : /item/1/sub_item/4/edit

I declared the following route :

entity.sub_item.edit_form:
  path: '/item/{item}/sub_item/{sub_item}/edit'
  defaults:
    _entity_form: 'sub_item.edit'
    _title: 'Edit sub item'
  options:
    _admin_route: TRUE
    parameters:
      item:
        type: entity:item
        with_config_overrides: TRUE
      sub_item:
        type: entity:sub_item
        with_config_overrides: TRUE
  requirements:
    _permission: 'administer site configuration'

Edit and Delete links are generated by list builder from getOperations. The list builder is on the following route : /item/1/sub_items (this is the "collection" to show the sub-items attached to main item).

I was hoping that the fact the current URL contained item/{item} can be directly re-used by the link generator, but it's not the fact...

Symfony\Component\Routing\Exception\MissingMandatoryParametersException : Some mandatory parameters are missing ("item") to generate a URL for route "entity.sub_item.edit_form". in Drupal\Core\Routing\UrlGenerator->doGenerate() (line 181 of /core/lib/Drupal/Core/Routing/UrlGenerator.php).

I tried to build a specific htmlRouteProvider class for my sub-item entity class but in this case too, the routes are built when cache are cleared, and I don't have access to the item in the URL to set it...

So... My question is : I'm missing something to do it easily, or must I re-implement the "toUrl()" method of my sub-item entity class to include the new "item" parameter "on the fly" ?

Thanks in advance for any suggestion.

PS : it's the solution I have actually in my sub-item entity class :

  public function toUrl($rel = 'canonical', array $options = []) {
    $uri = parent::toUrl($rel, $options);
    $uri->setRouteParameter('item', \Drupal::routeMatch()->getRawParameter('item'));
    return $uri;
  }

But maybe a better solution can be found ?

Answer 1

I would override SubItem::urlRouteParameters() and make this independent from the current route match so that the entity can build links on all pages:

  protected function urlRouteParameters($rel) {
    $parameters = parent::urlRouteParameters($rel);
    // assuming the parent relationship is a reference field
    $parameters['item'] = $this->parent->target_id;
    // if the reference field is in the parent you have to run an entity query
    return $parameters;
  }