OPENEUROPA-1754: Add cacheablemetadata.

src/Plugin/Block/ContentLanguageBlock.php

@@ -4,6 +4,7 @@
 
 namespace Drupal\oe_multilingual\Plugin\Block;
 
+use Drupal\Core\Cache\CacheableMetadata;
 use Drupal\Core\Entity\ContentEntityInterface;
 use Drupal\Core\Path\PathMatcherInterface;
 use Drupal\Core\Language\LanguageManagerInterface;
@@ -82,17 +83,21 @@ public static function create(ContainerInterface $container, array $configuratio
    */
   public function build() {
     $build = [];
+    $cache = new CacheableMetadata();
 
     $entity = $this->multilingualHelper->getEntityFromCurrentRoute();
     // Bail out if there is no entity or if it's not a content entity.
     if (!$entity || !$entity instanceof ContentEntityInterface) {
       return $build;
     }
+    $cache->addCacheableDependency($entity);
 
     // Render the links only if the current entity translation language is not
     // the same as the current site language.
     $translation = $this->multilingualHelper->getCurrentLanguageEntityTranslation($entity);
+    $cache->addCacheableDependency($translation->language());
     if ($translation->language()->getId() === $this->languageManager->getCurrentLanguage()->getId()) {
+      $cache->applyTo($build);
       return $build;
     }
 
@@ -108,7 +113,7 @@ public function build() {
       ],
       '#set_active_class' => TRUE,
     ];
-
+    $cache->applyTo($build);
     return $build;
   }