Dependency injection in create() method of block plugin with derivatives

I am trying to extend the menu_block module to allow it to work with domains (via the domain module). In order to do this I am extending the MenuBlock class, and trying to access the domain.negotiator service from within getDerivativeID(). I am using the create() method to inject the service and store it to a $domainNegotiator property as follows:

  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    $instance = parent::create($container, $configuration, $plugin_id, $plugin_definition);
    $instance->domainNegotiator = $container->get('domain.negotiator');
    return $instance;
  }

When I attempt to call $this->domainNegotiator from within getDerivativeID() I get an error stating the property doesn't exist and I therefore cannot access methods on it. In debugging I was able to trace the issue to MenuBlock::defaultConfiguration() calling $this->getDerivativeID().

Default configuration is set in __construct() inside BlockPluginTrait (called in BlockBase), so ultimately it boils up to being called in my class's create() method.

I am able to work around this issue by using a non-injected version of the service in my getDerivativeID() method, however this isn't a great practice:

$active_domain = \Drupal::service('domain.negotiator')->getActiveDomain();

Is there a way to inject dependencies so they are available before calling parent::create() in my class's create() method?

The Drupal plugin system has four levels. Plugin definition, derivatives, configuration and finally the run-time instance.

As you can see in your error message you configure a specific plugin definition or a derivative of the plugin definition. This definition is static and you can't change it after you have configured it.

Only the run-time instance of the plugin can react on dynamic conditions like the active domain.

I was unable to figure out how to extend MenuBlock using only create(). I had to change to a __construct() and create() system, and returned static() from within create() while manually injecting the dependencies from both the MenuBlock and SystemMenuBlock classes. This is a bit less robust in that it will break if the MenuBlock class ever changes dependencies, however it still accomplishes the intended behavior of using an injected dependency within getDerivitiveId():

  public function __construct(array $configuration, $plugin_id, $plugin_definition, MenuLinkTreeInterface $menu_tree, MenuActiveTrailInterface $menu_active_trail, MenuParentFormSelectorInterface $menu_parent_form_selector, EntityTypeManagerInterface $entity_type_manager, DomainNegotiatorInterface $domain_negotiator) {
    $this->domainNegotiator = $domain_negotiator;
    $this->menuParentFormSelector = $menu_parent_form_selector;
    $this->entityTypeManager = $entity_type_manager;
    parent::__construct($configuration, $plugin_id, $plugin_definition, $menu_tree, $menu_active_trail);
  }

  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->get('menu.link_tree'),
      $container->get('menu.active_trail'),
      $container->get('menu.parent_form_selector'),
      $container->get('entity_type.manager'),
      $container->get('domain.negotiator'));
  }