Argument 2 passed to Drupal\jsonapi\Routing\Routes::Drupal\jsonapi\Routing\{closure}() must be an instance of Drupal\jsonapi\ResourceType\ResourceType, NULL given

Problem/Motivation

The following error has been reported multiple times:

Argument 2 passed to Drupal\jsonapi\Routing\Routes::Drupal\jsonapi\Routing\{closure}() must be an instance of Drupal\jsonapi\ResourceType\ResourceType, NULL given

The only potential source of this error is in Drupal\jsonapi\ResourceType\ResourceTypeRepository::getRelatableResourceTypesFromFieldDefinition():

    $has_target_bundles = isset($handler_settings['target_bundles']) && !empty($handler_settings['target_bundles']);
    $target_bundles = $has_target_bundles ?
      $handler_settings['target_bundles']
      : $this->getAllBundlesForEntityType($entity_type_id);

    return array_map(function ($target_bundle) use ($entity_type_id, $resource_types) {
      $type_name = "$entity_type_id--$target_bundle";
      return isset($resource_types[$type_name]) ? $resource_types[$type_name] : NULL;
    }, $target_bundles);

The two known reasons that NULL might be generated is if an entity reference field has handler settings referencing a missing target bundle or the resource type name has been overridden by JSON:API Extras.

Proposed resolution

Neither of these reasons is a bug in JSON:API, per se. Instead, they could be caused by bad configuration, a poorly defined custom base field, or by JSON:API Extras.

In order to help users suffering from those bugs, introduce exceptions that will pinpoint the source of the errors.

User interface changes

Nope.

API changes

Nope.

Data model changes

Nope.

Release notes snippet

N/a