Error: Call to a member function getEntityTypeId()

Ran into another error if the $arg variable turns out to be a proper EntityInterface object. I put in another check to see if it's a proper entity, just add it to the array, but, also check if it's an int/str to make sure it's safe to pass to entity load.

Still not sure about this solution as a whole, but, it's fixing errors for us at the moment.

I found this issue when installing Notification message to our side crashed a view with contextual filters in the URL.

The error in our case was this

The website encountered an unexpected error. Try again later.

Drupal\Component\Plugin\Exception\PluginNotFoundException: The "arg_0" entity type does not exist. in Drupal\Core\Entity\EntityTypeManager->getDefinition() (line 139 of core/lib/Drupal/Core/Entity/EntityTypeManager.php).

Drupal\Core\Entity\EntityTypeManager->getHandler() (Line: 192)
Drupal\Core\Entity\EntityTypeManager->getStorage() (Line: 129)
Drupal\notification_message\Cache\Context\RouteEntityUuidCacheContext->attachViewRouteEntities() (Line: 86)
Drupal\notification_message\Cache\Context\RouteEntityUuidCacheContext->entityCacheTagsFromRoute() (Line: 60)
Drupal\notification_message\Cache\Context\RouteEntityUuidCacheContext->getContext() (Line: 123)
Drupal\Core\Cache\Context\CacheContextsManager->convertTokensToKeys() (Line: 244)
Drupal\Core\Cache\VariationCache->createCacheIdFast() (Line: 175)
Drupal\Core\Cache\VariationCache->getRedirectChain() (Line: 35)
Drupal\Core\Cache\VariationCache->get() (Line: 71)
Drupal\Core\Render\RenderCache->get() (Line: 113)
Drupal\Core\Render\PlaceholderingRenderCache->get() (Line: 317)
Drupal\Core\Render\Renderer->doRender() (Line: 493)
Drupal\Core\Render\Renderer->doRender() (Line: 240)
Drupal\Core\Render\Renderer->render() (Line: 475)
Drupal\Core\Template\TwigExtension->escapeFilter() (Line: 122)
__TwigTemplate_a80a95a6a8c5a3904dde60ae71cea77e->block_page_pre_content() (Line: 171)
Twig\Template->displayBlock() (Line: 130)
__TwigTemplate_f0b5e2f7c622ad70fb53191694409337->doDisplay() (Line: 394)
Twig\Template->displayWithErrorHandling() (Line: 367)
Twig\Template->display() (Line: 61)
__TwigTemplate_a80a95a6a8c5a3904dde60ae71cea77e->doDisplay() (Line: 394)
Twig\Template->displayWithErrorHandling() (Line: 367)
Twig\Template->display() (Line: 39)
__TwigTemplate_9e59da2f5f2329765a9dfd034cd52843->doDisplay() (Line: 394)
Twig\Template->displayWithErrorHandling() (Line: 367)
Twig\Template->display() (Line: 379)
Twig\Template->render() (Line: 38)
Twig\TemplateWrapper->render() (Line: 39)
twig_render_template() (Line: 348)
Drupal\Core\Theme\ThemeManager->render() (Line: 480)
Drupal\Core\Render\Renderer->doRender() (Line: 240)
Drupal\Core\Render\Renderer->render() (Line: 475)
Drupal\Core\Template\TwigExtension->escapeFilter() (Line: 81)
__TwigTemplate_cba7f8237d6b6745d5fea617efe7d916->doDisplay() (Line: 394)
Twig\Template->displayWithErrorHandling() (Line: 367)
Twig\Template->display() (Line: 39)
__TwigTemplate_f020d8f0b6dad9d1f81515d1f59f880c->doDisplay() (Line: 394)
Twig\Template->displayWithErrorHandling() (Line: 367)
Twig\Template->display() (Line: 379)
Twig\Template->render() (Line: 38)
Twig\TemplateWrapper->render() (Line: 39)
twig_render_template() (Line: 348)
Drupal\Core\Theme\ThemeManager->render() (Line: 480)
Drupal\Core\Render\Renderer->doRender() (Line: 240)
Drupal\Core\Render\Renderer->render() (Line: 158)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 627)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 153)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse() (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray()
call_user_func() (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch() (Line: 186)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 58)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 704)
Drupal\Core\DrupalKernel->handle() (Line: 19)

The patch in this issue fixed the problem. I would be willing to mark this RTBC and mark it Major or even Critical because it causes a crash. I will see if I can come up with another suggestion how to fix this.

I tried to improve the code a bit and made some small improvements. Here is an attached patch with following changes.

1. Added a check for $route_object being null to avoid potential errors.
2. Used instanceof instead of is_a for checking if $arg is an instance of EntityInterface.
3. Some small style changes.

Tested that the issue is still resolved.

I opened a MR for this for easier review and commenting.

I'm marking this RTCB. It should be merged in because it breaks views easily using contextual filters. The patch solves the issue for handling the argument and adds validation for only passing entity types.