Adds a mechanism for subscribers to PageHeaderDisplayEvent to set the cache tags on the PageHeaderBlock.

src/Event/PageHeaderDisplayEvent.php

@@ -39,6 +39,13 @@ class PageHeaderDisplayEvent extends Event {
    */
   protected $visibility = TRUE;
 
+  /**
+   * Cache tags override.
+   *
+   * @var array|null
+   */
+  protected $cacheTags = NULL;
+
   /**
    * {@inheritdoc}
    */
@@ -116,4 +123,23 @@ public function setVisibility($visibility) {
     $this->visibility = $visibility;
   }
 
+  /**
+   * Cache tags getter.
+   *
+   * @return array|null
+   */
+  public function getCacheTags() {
+    return $this->cacheTags;
+  }
+
+  /**
+   * Cache tags setter.
+   *
+   * @param array $cacheTags
+   *   The cache tags.
+   */
+  public function setCacheTags(array $cacheTags) {
+    $this->cacheTags = $cacheTags;
+  }
+
 }

src/Plugin/Block/PageHeaderBlock.php

@@ -83,6 +83,13 @@ class PageHeaderBlock extends BlockBase implements ContainerFactoryPluginInterfa
    */
   protected $visible;
 
+  /**
+   * Cache tags for this block.
+   *
+   * @var array
+   */
+  protected $cacheTags;
+
   /**
    * {@inheritdoc}
    */
@@ -126,10 +133,12 @@ public function __construct(array $configuration, $plugin_id, $plugin_definition
     $event = new PageHeaderDisplayEvent($this->entity);
     $this->eventDispatcher->dispatch($event, PageHeaderDisplayEvent::EVENT_NAME);
 
-    // Set the title, lede and visibility.
+    // Set the title, lede, visibility and cache tags.
     $this->title = is_null($event->getTitle()) ? $this->getTitle() : $event->getTitle();
     $this->lede = is_null($event->getLede()) ? $this->getLede() : $event->getLede();
     $this->visible = $event->getVisibility();
+    $entityCacheTags = is_null($this->entity) ? [] : $this->entity->getCacheTags();
+    $this->cacheTags = is_null($event->getCacheTags()) ? $entityCacheTags : $event->getCacheTags();
   }
 
   /**
@@ -214,8 +223,8 @@ public function defaultConfiguration() {
    * {@inheritdoc}
    */
   public function getCacheTags() {
-    if (!is_null($this->entity)) {
-      return Cache::mergeTags(parent::getCacheTags(), $this->entity->getCacheTags());
+    if (!empty($this->cacheTags)) {
+      return Cache::mergeTags(parent::getCacheTags(), $this->cacheTags);
     }
     return parent::getCacheTags();
   }

tests/localgov_core_page_header_event_test/src/EventSubscriber/PageHeaderSubscriber.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\localgov_core_page_header_event_test\EventSubscriber;
 
+use Drupal\Core\Cache\Cache;
 use Drupal\node\Entity\Node;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Drupal\localgov_core\Event\PageHeaderDisplayEvent;
@@ -27,20 +28,29 @@ public static function getSubscribedEvents() {
    */
   public function setPageHeader(PageHeaderDisplayEvent $event) {
 
+    $node = $event->getEntity();
+
+    if (!$node instanceof Node) {
+      return;
+    }
+
     // Override title and lede for page1 node content types.
-    if ($event->getEntity() instanceof Node &&
-      $event->getEntity()->bundle() == 'page1'
-    ) {
+    if ($node->bundle() == 'page1') {
       $event->setTitle('Overridden title');
       $event->setLede('Overridden lede');
     }
 
     // Hide page header block for page2 content types.
-    if ($event->getEntity() instanceof Node &&
-      $event->getEntity()->bundle() == 'page2'
-    ) {
+    if ($node->bundle() == 'page2') {
       $event->setVisibility(FALSE);
     }
+
+    // Set lede from summary, and cache tags from the parent for page3 nodes.
+    if ($node->bundle() == 'page3') {
+      $parent = $node->parent->entity;
+      $event->setLede($parent->body->summary);
+      $event->setCacheTags(Cache::mergeTags($node->getCacheTags(), $parent->getCacheTags()));
+    }
   }
 
 }

tests/src/Functional/PageHeaderBlockTest.php

@@ -2,12 +2,15 @@
 
 namespace Drupal\Tests\localgov_core\Functional;
 
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\node\NodeInterface;
 use Drupal\taxonomy\Entity\Term;
 use Drupal\Tests\BrowserTestBase;
 use Drupal\Tests\node\Traits\NodeCreationTrait;
 use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
 
+
 /**
  * Functional tests for LocalGovDrupal install profile.
  */
@@ -119,6 +122,67 @@ public function testPageHeaderDisplayEvent() {
     $this->assertSession()->pageTextNotContains($summary);
     $this->assertSession()->responseNotContains('<h1 class="header">Overridden title</h1>');
     $this->assertSession()->pageTextNotContains('Overridden lede');
+
+    // Check cache tags override.
+    // Set up a page3 that can reference other page3 nodes.
+    $this->createContentType(['type' => 'page3']);
+
+    FieldStorageConfig::create([
+      'field_name' => 'parent',
+      'entity_type' => 'node',
+      'type' => 'entity_reference',
+      'cardinality' => -1,
+      'settings' => [
+        'target_type' => 'node',
+      ],
+    ])->save();
+
+    FieldConfig::create([
+      'field_name' => 'parent',
+      'entity_type' => 'node',
+      'bundle' => 'page3',
+      'label' => 'Parent',
+      'cardinality' => -1,
+    ])->save();
+
+    $page3parent = $this->createNode([
+      'type' => 'page3',
+      'title' => 'page 3 parent title',
+      'body' => [
+        'summary' => 'page 3 parent summary',
+        'value' => '',
+      ],
+      'status' => NodeInterface::PUBLISHED,
+    ]);
+
+    $page3child = $this->createNode([
+      'type' => 'page3',
+      'title' => 'page 3 child title',
+      'body' => [
+        'summary' => 'page 3 child summary',
+        'value' => '',
+      ],
+      'parent' => [
+        'target_id' => $page3parent->id(),
+      ],
+      'status' => NodeInterface::PUBLISHED,
+    ]);
+
+    // Load the child page.
+    $this->drupalGet($page3child->toUrl()->toString());
+
+    // Check the child page contains the parent summary.
+    $this->assertSession()->pageTextContains('page 3 parent summary');
+
+    // Update the parent summary.
+    $page3parent->body->summary = 'page 3 parent updated summary';
+    $page3parent->save();
+
+    // Reload the child page.
+    $this->drupalGet($page3child->toUrl()->toString());
+
+    // Check the child page contains the updated parent summary.
+    $this->assertSession()->pageTextContains('page 3 parent updated summary');
   }
 
 }