Created a model class to move entity hook functions out of .module file.

rng.module

@@ -190,51 +190,9 @@ function _rng_entity_postsave(EntityInterface $entity) {
  * Implements hook_entity_predelete().
  */
 function rng_entity_predelete(EntityInterface $entity) {
-  /** @var \Drupal\courier\Service\IdentityChannelManagerInterface $icm */
-  $icm = \Drupal::service('plugin.manager.identity_channel');
-  if (in_array($entity->getEntityType(), $icm->getIdentityTypes())) {
-    // Remove registrant references to this identity.
-    $registrant_ids = Registrant::getRegistrantsIdsForIdentity($entity);
-    foreach (Registrant::loadMultiple($registrant_ids) as $registrant) {
-      $registrant->clearIdentity();
-      $registrant->save();
-    }
-  }
-
-  // Delete related entities when an event is deleted.
-  /** @var \Drupal\rng\EventManagerInterface $event_manager */
-  $event_manager = \Drupal::service('rng.event_manager');
-  try{
-    $event_meta = $event_manager->getMeta($entity);
-
-    // Delete registrations.
-    \Drupal::entityTypeManager()
-      ->getStorage('registration')
-      ->delete($event_meta->getRegistrations());
-
-    // Delete groups.
-    \Drupal::entityTypeManager()
-      ->getStorage('registration_group')
-      ->delete($event_meta->getGroups());
-
-    // Delete rules.
-    \Drupal::entityTypeManager()
-      ->getStorage('rng_rule')
-      ->delete($event_meta->getRules(NULL, FALSE, NULL));
-  }
-  // Not an event, thrown by getMeta().
-  catch (InvalidEventException $e) { }
-
-  if ($entity instanceof RuleComponentInterface) {
-    // Delete a TemplateCollection if the entity is a component with
-    // configuration for 'rng_courier_message'.
-    if ($entity->getPluginId() == 'rng_courier_message') {
-      $action = $entity->createInstance();
-      if (($action instanceof CourierTemplateCollection) && ($template_collection = $action->getTemplateCollection())) {
-        $template_collection->delete();
-      }
-    }
-  }
+  /** @var \Drupal\rng\RngModel $rng_model */
+  $rng_model = \Drupal::service('rng.entity.model');
+  $rng_model->hook_entity_predelete($entity);
 }
 
 /**

rng.services.yml

@@ -6,6 +6,9 @@ services:
     class: Drupal\rng\EventManager
     arguments: ['@entity.manager']
     parent: container.trait
+  rng.entity.model:
+    class: Drupal\rng\RngModel
+    arguments: ['@rng.event_manager', '@plugin.manager.identity_channel']
   rng.registrant.factory:
     class: Drupal\rng\RegistrantFactory
     arguments: ['@entity_type.manager', '@rng.event_manager']

src/RngModel.php

@@ -0,0 +1,162 @@
+<?php
+
+namespace Drupal\rng;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\courier\Service\IdentityChannelManagerInterface;
+use Drupal\rng\Entity\Registrant;
+use Drupal\rng\Plugin\Action\CourierTemplateCollection;
+
+/**
+ * Enforces RNG model relationships.
+ */
+class RngModel {
+
+  /**
+   * Storage for registration entities.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $registrationStorage;
+
+  /**
+   * Storage for registrant entities.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $registrantStorage;
+
+  /**
+   * Storage for registration group entities.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $registrationGroupStorage;
+
+  /**
+   * Storage for RNG rule entities.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $ruleStorage;
+
+  /**
+   * The RNG event manager.
+   *
+   * @var \Drupal\rng\EventManagerInterface
+   */
+  protected $eventManager;
+
+  /**
+   * The identity channel manager.
+   *
+   * @var \Drupal\courier\Service\IdentityChannelManagerInterface
+   */
+  protected $identityChannelManager;
+
+  /**
+   * Constructs a new RegistrantFactory object.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager.
+   * @param \Drupal\rng\EventManagerInterface $event_manager
+   *   The RNG event manager.
+   * @param \Drupal\courier\Service\IdentityChannelManagerInterface $identity_channel_manager
+   *   The identity channel manager.
+   */
+  public function __construct(EntityTypeManagerInterface $entity_type_manager, EventManagerInterface $event_manager, IdentityChannelManagerInterface $identity_channel_manager) {
+    $this->registrationStorage = $entity_type_manager->getStorage('registration');
+    $this->registrantStorage = $entity_type_manager->getStorage('registrant');
+    $this->registrationGroupStorage = $entity_type_manager->getStorage('registration_group');
+    $this->ruleStorage = $entity_type_manager->getStorage('rng_rule');
+    $this->eventManager = $event_manager;
+    $this->identityChannelManager = $identity_channel_manager;
+  }
+
+  /**
+   * React to Drupal `hook_entity_predelete` hook.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $entity
+   *   The entity object for the entity that is about to be deleted.
+   *
+   * @see hook_entity_predelete();
+   */
+  public function hook_entity_predelete(EntityInterface $entity) {
+    if (in_array($entity->getEntityType(), $this->identityChannelManager->getIdentityTypes())) {
+      $this->deletePerson($entity);
+    }
+
+    if ($this->eventManager->isEvent($entity)) {
+      $this->deleteRngEvent($entity);
+    }
+
+    if ($entity instanceof RuleComponentInterface) {
+      $this->deleteRngRuleComponent($entity);
+    }
+  }
+
+  /**
+   * Delete related entities when a person entity.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $entity
+   *   An identity/person entity.
+   */
+  protected function deletePerson(EntityInterface $entity) {
+    // Remove registrant references to this identity.
+    $registrant_ids = Registrant::getRegistrantsIdsForIdentity($entity);
+    foreach ($this->registrantStorage->loadMultiple($registrant_ids) as $registrant) {
+      /** @var \Drupal\rng\RegistrantInterface $registrant */
+      $registrant->clearIdentity();
+      $registrant->save();
+    }
+  }
+
+  /**
+   * Delete related entities when an event is deleted.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $entity
+   *   An RNG event entity.
+   */
+  protected function deleteRngEvent(EntityInterface $entity) {
+    // Don't need to catch exception from getMeta(), it is already checked by
+    // the calling method.
+    $event_meta = $this->eventManager->getMeta($entity);
+
+    // Delete registrations.
+    $registrations = $event_meta->getRegistrations();
+    $this->registrationStorage
+      ->delete($registrations);
+
+    // Delete groups.
+    $groups = $event_meta->getGroups();
+    $this->registrationGroupStorage
+      ->delete($groups);
+
+    // Delete rules.
+    $rules = $event_meta->getRules(NULL, FALSE, NULL);
+    $this->ruleStorage
+      ->delete($rules);
+  }
+
+  /**
+   * Delete related entities when a rule component entity is deleted.
+   *
+   * @param \Drupal\rng\RuleComponentInterface $entity
+   *   An RNG rule component entity.
+   */
+  protected function deleteRngRuleComponent(RuleComponentInterface $entity) {
+    // Delete a TemplateCollection if the entity is a component with
+    // configuration for 'rng_courier_message'.
+    if ('rng_courier_message' == $entity->getPluginId()) {
+      $action = $entity->createInstance();
+      if ($action instanceof CourierTemplateCollection) {
+        $template_collection = $action->getTemplateCollection();
+        if ($template_collection) {
+          $template_collection->delete();
+        }
+      }
+    }
+  }
+
+}