Persistent Null Reference Error in Block Content Entities Following Update from Core 10.2.4 to 10.2.5 or 10.2.6

For general debugging, here are a series of steps to take that increase in complexity. Start at the first step then continue if you can't solve it there.

1. Post the complete error message here, including line numbers.
2. Post the stack trace here. Sometimes that alone points to the cause.
3. Use a PHP debugger like Xdebug to stop execution in the function that throws the exception. Examine the call stack and values.
4. Execute `git bisect` on Drupal Core to identify the commit that changed behavior.

I am adding complete error message here, including line numbers. Thank you @cilefen for your feedback.
The website encountered an unexpected error. Try again later.

Error: Call to a member function label() on null in Drupal\block_content\Plugin\Derivative\BlockContent->getDerivativeDefinitions() (line 52 of core/modules/block_content/src/Plugin/Derivative/BlockContent.php).
Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator->getDerivatives(Array) (Line: 87)
Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator->getDefinitions() (Line: 323)
Drupal\Core\Plugin\DefaultPluginManager->findDefinitions() (Line: 205)
Drupal\Core\Plugin\DefaultPluginManager->getDefinitions() (Line: 22)
Drupal\Core\Plugin\DefaultPluginManager->getDefinition('block_content:2f516acc-dd9d-44cf-b764-ac9c80821252') (Line: 16)
Drupal\Core\Plugin\Factory\ContainerFactory->createInstance('block_content:2f516acc-dd9d-44cf-b764-ac9c80821252', Array) (Line: 76)
Drupal\Component\Plugin\PluginManagerBase->createInstance('block_content:2f516acc-dd9d-44cf-b764-ac9c80821252', Array) (Line: 62)
Drupal\Core\Plugin\DefaultSingleLazyPluginCollection->initializePlugin('block_content:2f516acc-dd9d-44cf-b764-ac9c80821252') (Line: 57)
Drupal\block\BlockPluginCollection->initializePlugin('block_content:2f516acc-dd9d-44cf-b764-ac9c80821252') (Line: 80)
Drupal\Component\Plugin\LazyPluginCollection->get('block_content:2f516acc-dd9d-44cf-b764-ac9c80821252') (Line: 45)
Drupal\block\BlockPluginCollection->get('block_content:2f516acc-dd9d-44cf-b764-ac9c80821252') (Line: 83)
Drupal\Core\Plugin\DefaultSingleLazyPluginCollection->setConfiguration(Array) (Line: 99)
Drupal\Core\Plugin\DefaultSingleLazyPluginCollection->addInstanceId('block_content:2f516acc-dd9d-44cf-b764-ac9c80821252', Array) (Line: 55)
Drupal\Core\Plugin\DefaultSingleLazyPluginCollection->__construct(Object, 'block_content:2f516acc-dd9d-44cf-b764-ac9c80821252', Array) (Line: 34)
Drupal\block\BlockPluginCollection->__construct(Object, 'block_content:2f516acc-dd9d-44cf-b764-ac9c80821252', Array, 'aboutusmenuheader') (Line: 156)
Drupal\block\Entity\Block->getPluginCollection() (Line: 145)
Drupal\block\Entity\Block->getPlugin() (Line: 118)
Drupal\block\BlockAccessControlHandler->checkAccess(Object, 'view', Object) (Line: 109)
Drupal\Core\Entity\EntityAccessControlHandler->access(Object, 'view', Object, 1) (Line: 329)
Drupal\Core\Entity\EntityBase->access('view', NULL, 1) (Line: 63)
Drupal\block\BlockRepository->getVisibleBlocksPerRegion(Array) (Line: 137)
Drupal\block\Plugin\DisplayVariant\BlockPageVariant->build() (Line: 270)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 128)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 186)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 53)
Asm89\Stack\Cors->handle(Object, 1, 1) (Line: 50)
Drupal\ban\BanMiddleware->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 704)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

I found additional information regarding the error while traced through our server logs.

Error Log Entry:

WARNING: [pool www] child 7000 said into stderr: "NOTICE: PHP message: Uncaught PHP Exception Error: "Call to a member function label() on null" at /var/www/html/docroot/core/modules/block_content/src/Plugin/Derivative/BlockContent.php line 52"
2024/05/08 15:42:46 [error] 2069#2069: *227 FastCGI sent in stderr: "PHP message: Uncaught PHP Exception Error: "Call to a member function label() on null" at /var/www/html/docroot/core/modules/block_content/src/Plugin/Derivative/BlockContent.php line 52" while reading response header from upstream, client: 172.18.0.5, server: , request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/run/php-fpm.sock:", host: "www.mydomain.com"

Code Location:
The error is consistently pointing to line 52 in /var/www/html/docroot/core/modules/block_content/src/Plugin/Derivative/BlockContent.php, where there seems to be a null object reference issue when attempting to access the label() function.

      1 <?php
      2 
      3 namespace Drupal\block_content\Plugin\Derivative;
      4 
      5 use Drupal\Component\Plugin\Derivative\DeriverBase;
      6 use Drupal\Core\Entity\EntityStorageInterface;
      7 use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
      8 use Symfony\Component\DependencyInjection\ContainerInterface;
      9 
     10 /**
     11  * Retrieves block plugin definitions for all content blocks.
     12  */
     13 class BlockContent extends DeriverBase implements ContainerDeriverInterface {
     14 
     15   /**
     16    * The content block storage.
     17    *
     18    * @var \Drupal\Core\Entity\EntityStorageInterface
     19    */
     20   protected $blockContentStorage;
     21 
     22   /**
     23    * Constructs a BlockContent object.
     24    *
     25    * @param \Drupal\Core\Entity\EntityStorageInterface $block_content_storage
     26    *   The content block storage.
     27    */
     28   public function __construct(EntityStorageInterface $block_content_storage) {
     29     $this->blockContentStorage = $block_content_storage;
     30   }
     31 
     32   /**
     33    * {@inheritdoc}
     34    */
     35   public static function create(ContainerInterface $container, $base_plugin_id) {
     36     $entity_type_manager = $container->get('entity_type.manager');
     37     return new static(
     38       $entity_type_manager->getStorage('block_content')
     39     );
     40   }
     41 
     42   /**
     43    * {@inheritdoc}
     44    */
     45   public function getDerivativeDefinitions($base_plugin_definition) {
     46     $block_contents = $this->blockContentStorage->loadByProperties(['reusable' => TRUE]);
     47     // Reset the discovered definitions.
     48     $this->derivatives = [];
     49     /** @var \Drupal\block_content\Entity\BlockContent $block_content */
     50     foreach ($block_contents as $block_content) {
     51       $this->derivatives[$block_content->uuid()] = $base_plugin_definition;
     52       $this->derivatives[$block_content->uuid()]['admin_label'] = $block_content->label() ?? ($block_content->type->entity->label() . ': ' . $block_cont     52 ent->id());
     53       $this->derivatives[$block_content->uuid()]['config_dependencies']['content'] = [
     54         $block_content->getConfigDependencyName(),
     55       ];
     56     }
     57     return parent::getDerivativeDefinitions($base_plugin_definition);
     58   }
     59 
     60 }

I would like to propose changes to the BlockContent.php file within the block_content module to handle potential null entity issues that have been causing errors in our environment.

Issue Description:
We have encountered a recurring error when the label() function is called on a null block_content entity. This results in a PHP exception "Call to a member function label() on null."

Proposed Changes:
To address this issue, I've implemented a null check before accessing the block_content entity's methods. Below is the diff of the changes made:

diff --git a/docroot/core/modules/block_content/src/Plugin/Derivative/BlockContent.php b/docroot/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
index 5ba836f1a8..73a99af376 100644
--- a/docroot/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
+++ b/docroot/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
@@ -48,13 +48,19 @@ public function getDerivativeDefinitions($base_plugin_definition) {
     $this->derivatives = [];
     /** @var \Drupal\block_content\Entity\BlockContent $block_content */
     foreach ($block_contents as $block_content) {
-      $this->derivatives[$block_content->uuid()] = $base_plugin_definition;
-      $this->derivatives[$block_content->uuid()]['admin_label'] = $block_content->label();
-      $this->derivatives[$block_content->uuid()]['config_dependencies']['content'] = [
-        $block_content->getConfigDependencyName(),
-      ];
+      if ($block_content !== null) {
+        $uuid = $block_content->uuid();
+        $this->derivatives[$uuid] = $base_plugin_definition;
+        // Use null coalescing operator to safely attempt to call label()
+        $this->derivatives[$uuid]['admin_label'] = $block_content->label() ?? 'Default Label';
+        $this->derivatives[$uuid]['config_dependencies']['content'] = [
+          $block_content->getConfigDependencyName(),
+        ];
+      } else {
+        // Optionally log or handle the case when block_content is unexpectedly null
+        \Drupal::logger('block_content')->warning('Encountered a null block content entity.');
+      }
     }
     return parent::getDerivativeDefinitions($base_plugin_definition);
   }
-
 }

I am looking forward a feedback on this patch. If deemed suitable, I would appreciate guidance on the formal submission process for these changes to the Drupal community.

Thank you for your attention and support.

Mario

This is a bug report that needs steps to reproduce. Why is the value null?

Also: the way to propose changes is with a pull request.

I have created and attached a patch that addresses the null reference error in BlockContent.php. I have thoroughly tested it in my environment, and it resolves the issue effectively.

Please find the patch attached for review. I welcome any feedback or additional testing from the community to ensure the change meets all necessary criteria and does not introduce any regressions.

Thank you for reviewing this patch.

Can you turn to an MR please

🐛 Prevent empty block_content info fields from causing php deprecation notices when placing blocks with no label. Fixed may be related

That line has 2 calls to ->label() it would be good to know which one is throwing the error. I.e is loadByProperties() returning NULL, or is $block_content->type->entity returning NULL.

If it's the former then that's a larger issue, if it's the latter then it means the block content type for your block no longer exists which is an issue with your site.

We need steps to reproduce from a fresh installation. The current steps are not sufficient to reproduce the bug.

Should be PMNMI