Fatal error deleting host entity when wait list enabled
>>> [!note] Migrated issue
<!-- Drupal.org comment -->
<!-- Migrated from issue #3570197. -->
Reported by: [ryan-l-robinson](https://www.drupal.org/user/3684696)
Related to !181
>>>
<h3 id="summary-problem-motivation">Problem/Motivation</h3>
<p>I got this error when I tried to delete a node that had registrations on it:</p>
<pre>The website encountered an unexpected error. Try again later.<br><br>Error: Call to a member function getSetting() on null in Drupal\registration_waitlist\EventSubscriber\RegistrationEventSubscriber->onDelete() (line 80 of modules/contrib/registration/modules/registration_waitlist/src/EventSubscriber/RegistrationEventSubscriber.php).<br>Symfony\Component\EventDispatcher\EventDispatcher::Symfony\Component\EventDispatcher\{closure}(Object, 'registration.registration.delete', Object) (Line: 206)<br>Symfony\Component\EventDispatcher\EventDispatcher->callListeners(Array, 'registration.registration.delete', Object) (Line: 56)<br>Symfony\Component\EventDispatcher\EventDispatcher->dispatch(Object, 'registration.registration.delete') (Line: 57)<br>Drupal\registration\RegistrationStorage->invokeHook('delete', Object) (Line: 501)<br>Drupal\Core\Entity\EntityStorageBase->delete(Array) (Line: 753)<br>Drupal\Core\Entity\Sql\SqlContentEntityStorage->delete(Array) (Line: 132)<br>Drupal\registration_purger\RegistrationPurger->purgeRegistrations(Object) (Line: 75)<br>Drupal\registration_purger\RegistrationPurger->onEntityDelete(Object) (Line: 14)<br>registration_purger_entity_delete(Object)<br>call_user_func_array('registration_purger_entity_delete', Array) (Line: 389)<br>Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}('registration_purger_entity_delete', 'registration_purger') (Line: 340)<br>Drupal\Core\Extension\ModuleHandler->invokeAllWith('entity_delete', Object) (Line: 388)<br>Drupal\Core\Extension\ModuleHandler->invokeAll('entity_delete', Array) (Line: 221)<br>Drupal\Core\Entity\EntityStorageBase->invokeHook('delete', Object) (Line: 1038)<br>Drupal\Core\Entity\ContentEntityStorageBase->invokeHook('delete', Object) (Line: 501)<br>Drupal\Core\Entity\EntityStorageBase->delete(Array) (Line: 753)<br>Drupal\Core\Entity\Sql\SqlContentEntityStorage->delete(Array) (Line: 378)<br>Drupal\Core\Entity\EntityBase->delete() (Line: 71)<br>Drupal\Core\Entity\ContentEntityDeleteForm->submitForm(Array, Object) (Line: 108)<br>Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object) (Line: 45)<br>Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object) (Line: 615)<br>Drupal\Core\Form\FormBuilder->processForm('node_event_delete_form', Array, Object) (Line: 347)<br>Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)<br>Drupal\Core\Controller\FormController->getContentResult(Object, Object)<br>call_user_func_array(Array, Array) (Line: 123)<br>Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 634)<br>Drupal\Core\Render\Renderer::Drupal\Core\Render\{closure}()<br>Fiber->resume() (Line: 649)<br>Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 121)<br>Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)<br>Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 183)<br>Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)<br>Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 53)<br>Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)<br>Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 28)<br>Drupal\Core\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 32)<br>Drupal\big_pipe\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 118)<br>Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 92)<br>Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 50)<br>Drupal\ban\BanMiddleware->handle(Object, 1, 1) (Line: 48)<br>Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)<br>Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 53)<br>Drupal\Core\StackMiddleware\AjaxPageState->handle(Object, 1, 1) (Line: 54)<br>Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 745)<br>Drupal\Core\DrupalKernel->handle(Object) (Line: 19)</pre><h4 id="summary-steps-reproduce">Steps to reproduce</h4>
<p>Drupal 11.3.2</p>
<p>PHP 8.3</p>
<p>Install registration, registration_waitlist, and registration_purger</p>
<p>Might need to have some registrations on the node while trying to delete it; I don't think I got any error when I tried deleting an event node earlier that did not have any registrations on it.</p>
<h3 id="summary-proposed-resolution">Proposed resolution</h3>
<p>I just encountered this a few minutes ago and haven't done deep tests, but my guess at this point is that what is happening is this order of operations:</p>
<p>1. Node gets deleted.<br>
2. Registrations start being purged.<br>
3. Once one registration is deleted, that means there's room to move another from the waitlist to complete and it tries to do so.<br>
4. Except that the node it is trying to use that for, the $host_entity at the identified line 80, no longer exists.</p>
<p>If that's true, that solution might just be a type check to confirm that $host_entity is an instance of HostEntityInterface, not null, before proceeding to get its settings.</p>
<p>If I find some time, I'll come back and see what I can do for testing a solution, but in the meantime I'm happy for those more knowledgeable to run with it.</p>
issue
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