Issue #2512718 by Berdir, pfrenssen, Wim Leers, Fabianx, dawehner, catch, effulgentsia, plach, Gábor Hojtsy: EntityManager::getTranslationFromContext() should add the content language cache context to the entity

core/lib/Drupal/Core/Access/AccessResult.php

@@ -25,6 +25,9 @@ use Drupal\Core\Session\AccountInterface;
  *
  * When using ::orIf() and ::andIf(), cacheability metadata will be merged
  * accordingly as well.
+ *
+ * @todo Use RefinableCacheableDependencyInterface and the corresponding trait in
+ *   https://www.drupal.org/node/2526326.
  */
 abstract class AccessResult implements AccessResultInterface, CacheableDependencyInterface {
 

core/lib/Drupal/Core/Cache/CacheableMetadata.php

@@ -10,6 +10,9 @@ namespace Drupal\Core\Cache;
  * Defines a generic class for passing cacheability metadata.
  *
  * @ingroup cache
+ *
+ * @todo Use RefinableCacheableDependencyInterface and the corresponding trait in
+ *   https://www.drupal.org/node/2526326.
  */
 class CacheableMetadata implements CacheableDependencyInterface {
 

core/lib/Drupal/Core/Cache/RefinableCacheableDependencyInterface.php

@@ -0,0 +1,55 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\Core\Cache\RefinableCacheableDependencyInterface.
+ */
+
+namespace Drupal\Core\Cache;
+
+/**
+ * Allows to add cacheability metadata to an object for the current runtime.
+ *
+ * This must be used when changing an object in a way that affects its
+ * cacheability. For example, when changing the active translation of an entity
+ * based on the current content language then a cache context for that must be
+ * added.
+ */
+interface RefinableCacheableDependencyInterface extends CacheableDependencyInterface {
+
+  /**
+   * Adds cache contexts.
+   *
+   * @param string[] $cache_contexts
+   *   The cache contexts to be added.
+   *
+   * @return $this
+   */
+  public function addCacheContexts(array $cache_contexts);
+
+  /**
+   * Adds cache tags.
+   *
+   * @param string[] $cache_tags
+   *   The cache tags to be added.
+   *
+   * @return $this
+   */
+  public function addCacheTags(array $cache_tags);
+
+  /**
+   * Merges the maximum age (in seconds) with the existing maximum age.
+   *
+   * The max age will be set to the given value if it is lower than the existing
+   * value.
+   *
+   * @param int $max_age
+   *   The max age to associate.
+   *
+   * @return $this
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown if a non-integer value is supplied.
+   */
+  public function mergeCacheMaxAge($max_age);
+
+}

core/lib/Drupal/Core/Cache/RefinableCacheableDependencyTrait.php

@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Cache\RefinableCacheableDependencyTrait.
+ */
+
+namespace Drupal\Core\Cache;
+
+/**
+ * Trait for \Drupal\Core\Cache\RefinableCacheableDependencyInterface.
+ */
+trait RefinableCacheableDependencyTrait {
+
+  /**
+   * Cache contexts.
+   *
+   * @var string[]
+   */
+  protected $cacheContexts = [];
+
+  /**
+   * Cache tags.
+   *
+   * @var string[]
+   */
+  protected $cacheTags = [];
+
+  /**
+   * Cache max-age.
+   *
+   * @var int
+   */
+  protected $cacheMaxAge = Cache::PERMANENT;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addCacheContexts(array $cache_contexts) {
+    $this->cacheContexts = Cache::mergeContexts($this->cacheContexts, $cache_contexts);
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addCacheTags(array $cache_tags) {
+    $this->cacheTags = Cache::mergeTags($this->cacheTags, $cache_tags);
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function mergeCacheMaxAge($max_age) {
+    $this->cacheMaxAge = Cache::mergeMaxAges($this->cacheMaxAge, $max_age);
+    return $this;
+  }
+
+}

core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php

@@ -193,7 +193,7 @@ abstract class ConfigEntityBase extends Entity implements ConfigEntityInterface
    */
   public function disable() {
     // An entity was disabled, invalidate its own cache tag.
-    Cache::invalidateTags($this->getCacheTags());
+    Cache::invalidateTags($this->getCacheTagsToInvalidate());
     return $this->setStatus(FALSE);
   }
 
@@ -409,7 +409,7 @@ abstract class ConfigEntityBase extends Entity implements ConfigEntityInterface
   /**
    * {@inheritdoc}
    */
-  public function getCacheTags() {
+  public function getCacheTagsToInvalidate() {
     // Use cache tags that match the underlying config object's name.
     // @see \Drupal\Core\Config\ConfigBase::getCacheTags()
     return ['config:' . $this->getConfigDependencyName()];

core/lib/Drupal/Core/Datetime/Entity/DateFormat.php

@@ -101,7 +101,7 @@ class DateFormat extends ConfigEntityBase implements DateFormatInterface {
   /**
    * {@inheritdoc}
    */
-  public function getCacheTags() {
+  public function getCacheTagsToInvalidate() {
     return ['rendered'];
   }
 

core/lib/Drupal/Core/Entity/Entity.php

@@ -8,6 +8,7 @@
 namespace Drupal\Core\Entity;
 
 use Drupal\Core\Cache\Cache;
+use Drupal\Core\Cache\RefinableCacheableDependencyTrait;
 use Drupal\Core\DependencyInjection\DependencySerializationTrait;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Component\Utility\Unicode;
@@ -24,6 +25,8 @@ use Drupal\Core\Url;
  */
 abstract class Entity implements EntityInterface {
 
+  use RefinableCacheableDependencyTrait;
+
   use DependencySerializationTrait {
     __sleep as traitSleep;
   }
@@ -440,23 +443,36 @@ abstract class Entity implements EntityInterface {
    * {@inheritdoc}
    */
   public function getCacheContexts() {
-    return [];
+    return $this->cacheContexts;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getCacheTags() {
+  public function getCacheTagsToInvalidate() {
     // @todo Add bundle-specific listing cache tag?
     //   https://www.drupal.org/node/2145751
+    if ($this->isNew()) {
+      return [];
+    }
     return [$this->entityTypeId . ':' . $this->id()];
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheTags() {
+    if ($this->cacheTags) {
+      return Cache::mergeTags($this->getCacheTagsToInvalidate(), $this->cacheTags);
+    }
+    return $this->getCacheTagsToInvalidate();
+  }
+
   /**
    * {@inheritdoc}
    */
   public function getCacheMaxAge() {
-    return Cache::PERMANENT;
+    return $this->cacheMaxAge;
   }
 
   /**
@@ -511,7 +527,7 @@ abstract class Entity implements EntityInterface {
     }
     if ($update) {
       // An existing entity was updated, also invalidate its unique cache tag.
-      $tags = Cache::mergeTags($tags, $this->getCacheTags());
+      $tags = Cache::mergeTags($tags, $this->getCacheTagsToInvalidate());
     }
     Cache::invalidateTags($tags);
   }
@@ -532,7 +548,7 @@ abstract class Entity implements EntityInterface {
       // other pages than the one it's on. The one it's on is handled by its own
       // cache tag, but subsequent list pages would not be invalidated, hence we
       // must invalidate its list cache tags as well.)
-      $tags = Cache::mergeTags($tags, $entity->getCacheTags());
+      $tags = Cache::mergeTags($tags, $entity->getCacheTagsToInvalidate());
     }
     Cache::invalidateTags($tags);
   }

core/lib/Drupal/Core/Entity/EntityForm.php

@@ -101,6 +101,12 @@ class EntityForm extends FormBase implements EntityFormInterface {
       $this->init($form_state);
     }
 
+    // Ensure that edit forms have the correct cacheability metadata so they can
+    // be cached.
+    if (!$this->entity->isNew()) {
+      \Drupal::service('renderer')->addCacheableDependency($form, $this->entity);
+    }
+
     // Retrieve the form array using the possibly updated entity in form state.
     $form = $this->form($form, $form_state);
 

core/lib/Drupal/Core/Entity/EntityInterface.php

@@ -9,13 +9,14 @@ namespace Drupal\Core\Entity;
 
 use Drupal\Core\Access\AccessibleInterface;
 use Drupal\Core\Cache\CacheableDependencyInterface;
+use Drupal\Core\Cache\RefinableCacheableDependencyInterface;
 
 /**
  * Defines a common interface for all entity objects.
  *
  * @ingroup entity_api
  */
-interface EntityInterface extends AccessibleInterface, CacheableDependencyInterface {
+interface EntityInterface extends AccessibleInterface, CacheableDependencyInterface, RefinableCacheableDependencyInterface {
 
   /**
    * Gets the entity UUID (Universally Unique Identifier).
@@ -348,6 +349,19 @@ interface EntityInterface extends AccessibleInterface, CacheableDependencyInterf
    */
   public function getOriginalId();
 
+  /**
+   * Returns the cache tags that should be used to invalidate caches.
+   *
+   * This will not return additional cache tags added through addCacheTags().
+   *
+   * @return string[]
+   *   Set of cache tags.
+   *
+   * @see \Drupal\Core\Cache\RefinableCacheableDependencyInterface::addCacheTags()
+   * @see \Drupal\Core\Cache\CacheableDependencyInterface::getCacheTags()
+   */
+  public function getCacheTagsToInvalidate();
+
   /**
    * Sets the original ID.
    *

core/lib/Drupal/Core/Entity/EntityManager.php

@@ -969,6 +969,7 @@ class EntityManager extends DefaultPluginManager implements EntityManagerInterfa
     if ($entity instanceof TranslatableInterface && count($entity->getTranslationLanguages()) > 1) {
       if (empty($langcode)) {
         $langcode = $this->languageManager->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)->getId();
+        $entity->addCacheContexts(['languages:' . LanguageInterface::TYPE_CONTENT]);
       }
 
       // Retrieve language fallback candidates to perform the entity language

core/lib/Drupal/Core/Entity/EntityViewBuilder.php

@@ -117,14 +117,10 @@ class EntityViewBuilder extends EntityHandlerBase implements EntityHandlerInterf
    * {@inheritdoc}
    */
   public function viewMultiple(array $entities = array(), $view_mode = 'full', $langcode = NULL) {
-    if (!isset($langcode)) {
-      $langcode = $this->languageManager->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)->getId();
-    }
-
     $build_list = array(
       '#sorted' => TRUE,
       '#pre_render' => array(array($this, 'buildMultiple')),
-      '#langcode' => $langcode,
+      '#langcode' => $langcode ?: $this->languageManager->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)->getId(),
     );
     $weight = 0;
     foreach ($entities as $key => $entity) {
@@ -133,9 +129,10 @@ class EntityViewBuilder extends EntityHandlerBase implements EntityHandlerInterf
       $entity = $this->entityManager->getTranslationFromContext($entity, $langcode);
 
       // Set build defaults.
-      $build_list[$key] = $this->getBuildDefaults($entity, $view_mode, $langcode);
+      $entity_langcode = $entity->language()->getId();
+      $build_list[$key] = $this->getBuildDefaults($entity, $view_mode, $entity_langcode);
       $entityType = $this->entityTypeId;
-      $this->moduleHandler()->alter(array($entityType . '_build_defaults', 'entity_build_defaults'), $build_list[$key], $entity, $view_mode, $langcode);
+      $this->moduleHandler()->alter(array($entityType . '_build_defaults', 'entity_build_defaults'), $build_list[$key], $entity, $view_mode, $entity_langcode);
 
       $build_list[$key]['#weight'] = $weight++;
     }

core/modules/aggregator/src/Entity/Item.php

@@ -225,13 +225,13 @@ class Item extends ContentEntityBase implements ItemInterface {
     // handles the regular cases. The Item entity has one special case: a newly
     // created Item is *also* associated with a Feed, so we must invalidate the
     // associated Feed's cache tag.
-    Cache::invalidateTags($this->getCacheTags());
+    Cache::invalidateTags($this->getCacheTagsToInvalidate());
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getCacheTags() {
+  public function getCacheTagsToInvalidate() {
     return Feed::load($this->getFeedId())->getCacheTags();
   }
 

core/modules/block/src/Entity/Block.php

@@ -246,7 +246,7 @@ class Block extends ConfigEntityBase implements BlockInterface, EntityWithPlugin
     // so we must invalidate the associated block's cache tag (which includes
     // the theme cache tag).
     if (!$update) {
-      Cache::invalidateTags($this->getCacheTags());
+      Cache::invalidateTags($this->getCacheTagsToInvalidate());
     }
   }
 

core/modules/block/src/Tests/BlockViewBuilderTest.php

@@ -194,7 +194,7 @@ class BlockViewBuilderTest extends KernelTestBase {
 
     // Enable the block view alter hook that adds a suffix, for basic testing.
     \Drupal::state()->set('block_test_view_alter_suffix', TRUE);
-    Cache::invalidateTags($this->block->getCacheTags());
+    Cache::invalidateTags($this->block->getCacheTagsToInvalidate());
     $build = $this->getBlockRenderArray();
     $this->assertTrue(isset($build['#suffix']) && $build['#suffix'] === '<br>Goodbye!', 'A block with content is altered.');
     $this->assertIdentical($this->renderer->renderRoot($build), 'Llamas &gt; unicorns!<br>Goodbye!');
@@ -206,7 +206,7 @@ class BlockViewBuilderTest extends KernelTestBase {
     $request->setMethod('GET');
 
     \Drupal::state()->set('block_test.content', NULL);
-    Cache::invalidateTags($this->block->getCacheTags());
+    Cache::invalidateTags($this->block->getCacheTagsToInvalidate());
 
     $default_keys = array('entity_view', 'block', 'test_block');
     $default_tags = array('block_view', 'config:block.block.test_block');

core/modules/comment/src/CommentViewBuilder.php

@@ -71,11 +71,9 @@ class CommentViewBuilder extends EntityViewBuilder {
       ->getFieldDefinition($entity->getFieldName())
       ->getSetting('default_mode') === CommentManagerInterface::COMMENT_MODE_THREADED;
     // If threading is enabled, don't render cache individual comments, but do
-    // keep the cache tags, so they can bubble up.
+    // keep the cacheability metadata, so it can bubble up.
     if ($build['#comment_threaded']) {
-      $cache_tags = $build['#cache']['tags'];
-      $build['#cache'] = [];
-      $build['#cache']['tags'] = $cache_tags;
+      unset($build['#cache']['keys']);
     }
 
     return $build;

core/modules/comment/src/Tests/CommentTranslationUITest.php

@@ -32,6 +32,18 @@ class CommentTranslationUITest extends ContentTranslationUITestBase {
    */
   protected $adminUser;
 
+  /**
+   * {inheritdoc}
+   */
+  protected $defaultCacheContexts = [
+    'languages:language_interface',
+    'theme',
+    'user.permissions',
+    'timezone',
+    'url.query_args.pagers:0',
+    'user.roles'
+  ];
+
   /**
    * Modules to install.
    *

core/modules/contact/src/Tests/Views/ContactLinkTest.php

@@ -86,7 +86,7 @@ class ContactLinkTest extends ViewTestBase {
     // Disable contact link for no_contact.
     $this->userData->set('contact', $no_contact_account->id(), 'enabled', FALSE);
     // @todo Remove cache invalidation in https://www.drupal.org/node/2477903.
-    Cache::invalidateTags($no_contact_account->getCacheTags());
+    Cache::invalidateTags($no_contact_account->getCacheTagsToInvalidate());
     $this->drupalGet('test-contact-link');
     $this->assertContactLinks($accounts, array('root', 'admin'));
   }

core/modules/content_translation/src/Tests/ContentTranslationUITestBase.php

@@ -7,18 +7,22 @@
 
 namespace Drupal\content_translation\Tests;
 
+use Drupal\Core\Cache\Cache;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Url;
 use Drupal\language\Entity\ConfigurableLanguage;
 use Drupal\Component\Utility\SafeMarkup;
+use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Tests the Content Translation UI.
  */
 abstract class ContentTranslationUITestBase extends ContentTranslationTestBase {
 
+  use AssertPageCacheContextsAndTagsTrait;
+
   /**
    * The id of the entity being translated.
    *
@@ -33,6 +37,15 @@ abstract class ContentTranslationUITestBase extends ContentTranslationTestBase {
    */
   protected $testLanguageSelector = TRUE;
 
+  /**
+   * Default cache contexts expected on a non-translated entity.
+   *
+   * Cache contexts will not be checked if this list is empty.
+   *
+   * @var string[]
+   */
+  protected $defaultCacheContexts = ['languages:language_interface', 'theme', 'user.permissions'];
+
   /**
    * Tests the basic translation UI.
    */
@@ -64,6 +77,11 @@ abstract class ContentTranslationUITestBase extends ContentTranslationTestBase {
     $this->assertTrue($entity, 'Entity found in the database.');
     $this->drupalGet($entity->urlInfo());
     $this->assertResponse(200, 'Entity URL is valid.');
+
+    // Ensure that the content language cache context is not yet added to the
+    // page.
+    $this->assertCacheContexts($this->defaultCacheContexts);
+
     $this->drupalGet($entity->urlInfo('drupal:content-translation-overview'));
     $this->assertNoText('Source language', 'Source language column correctly hidden.');
 
@@ -87,9 +105,14 @@ abstract class ContentTranslationUITestBase extends ContentTranslationTestBase {
     ], array('language' => $language));
     $this->drupalPostForm($add_url, $this->getEditValues($values, $langcode), $this->getFormSubmitActionForNewTranslation($entity, $langcode));
 
-    // Get the entity and reset its cache, so that the new translation gets the
-    // updated values.
+    // Ensure that the content language cache context is not yet added to the
+    // page.
     $entity = entity_load($this->entityTypeId, $this->entityId, TRUE);
+    $this->drupalGet($entity->urlInfo());
+    $this->assertCacheContexts(Cache::mergeContexts(['languages:language_content'], $this->defaultCacheContexts));
+
+    // Reset the cache of the entity, so that the new translation gets the
+    // updated values.
     $metadata_source_translation = $this->manager->getTranslationMetadata($entity->getTranslation($default_langcode));
     $metadata_target_translation = $this->manager->getTranslationMetadata($entity->getTranslation($langcode));
 

core/modules/image/src/Entity/ImageStyle.php

@@ -267,7 +267,7 @@ class ImageStyle extends ConfigEntityBase implements ImageStyleInterface, Entity
     // Clear caches so that formatters may be added for this style.
     drupal_theme_rebuild();
 
-    Cache::invalidateTags($this->getCacheTags());
+    Cache::invalidateTags($this->getCacheTagsToInvalidate());
 
     return $this;
   }

core/modules/menu_link_content/src/Tests/MenuLinkContentTranslationUITest.php

@@ -17,6 +17,11 @@ use Drupal\menu_link_content\Entity\MenuLinkContent;
  */
 class MenuLinkContentTranslationUITest extends ContentTranslationUITestBase {
 
+  /**
+   * {inheritdoc}
+   */
+  protected $defaultCacheContexts = ['languages:language_interface', 'theme', 'user.permissions', 'user.roles:authenticated'];
+
   /**
    * Modules to enable.
    *

core/modules/node/src/Tests/NodeTranslationUITest.php

@@ -21,6 +21,21 @@ use Drupal\language\Entity\ConfigurableLanguage;
  */
 class NodeTranslationUITest extends ContentTranslationUITestBase {
 
+  /**
+   * {inheritdoc}
+   */
+  protected $defaultCacheContexts = [
+    'languages:language_interface',
+    'theme',
+    'user.permissions',
+    'route.menu_active_trails:account',
+    'route.menu_active_trails:footer',
+    'route.menu_active_trails:main',
+    'route.menu_active_trails:tools',
+    'timezone',
+    'user.roles'
+  ];
+
   /**
    * Modules to enable.
    *

core/modules/shortcut/src/Entity/Shortcut.php

@@ -102,7 +102,7 @@ class Shortcut extends ContentEntityBase implements ShortcutInterface {
     // newly created shortcut is *also* added to a shortcut set, so we must
     // invalidate the associated shortcut set's cache tag.
     if (!$update) {
-      Cache::invalidateTags($this->getCacheTags());
+      Cache::invalidateTags($this->getCacheTagsToInvalidate());
     }
   }
 
@@ -178,7 +178,7 @@ class Shortcut extends ContentEntityBase implements ShortcutInterface {
   /**
    * {@inheritdoc}
    */
-  public function getCacheTags() {
+  public function getCacheTagsToInvalidate() {
     return $this->shortcut_set->entity->getCacheTags();
   }
 

core/modules/shortcut/src/Tests/ShortcutTranslationUITest.php

@@ -18,6 +18,11 @@ use Drupal\Core\Language\Language;
  */
 class ShortcutTranslationUITest extends ContentTranslationUITestBase {
 
+  /**
+   * {inheritdoc}
+   */
+  protected $defaultCacheContexts = ['languages:language_interface', 'theme', 'user'];
+
   /**
    * Modules to enable.
    *

core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php

@@ -571,7 +571,7 @@ abstract class EntityCacheTagsTestBase extends PageCacheTagsTestBase {
     // a cache miss for every route except the ones for the non-referencing
     // entity and the empty entity listing.
     $this->pass("Test invalidation of referenced entity's cache tag.", 'Debug');
-    Cache::invalidateTags($this->entity->getCacheTags());
+    Cache::invalidateTags($this->entity->getCacheTagsToInvalidate());
     $this->verifyPageCache($referencing_entity_url, 'MISS');
     $this->verifyPageCache($listing_url, 'MISS');
     $this->verifyPageCache($nonempty_entity_listing_url, 'MISS');

core/modules/system/src/Tests/Entity/EntityWithUriCacheTagsTestBase.php

@@ -121,7 +121,7 @@ abstract class EntityWithUriCacheTagsTestBase extends EntityCacheTagsTestBase {
     // Verify that after invalidating the entity's cache tag directly, there is
     // a cache miss.
     $this->pass("Test invalidation of entity's cache tag.", 'Debug');
-    Cache::invalidateTags($this->entity->getCacheTags());
+    Cache::invalidateTags($this->entity->getCacheTagsToInvalidate());
     $this->verifyPageCache($entity_url, 'MISS');
 
     // Verify a cache hit.

core/modules/views/src/Plugin/views/cache/CachePluginBase.php

@@ -153,7 +153,7 @@ abstract class CachePluginBase extends PluginBase {
    * Clear out cached data for a view.
    */
   public function cacheFlush() {
-    Cache::invalidateTags($this->view->storage->getCacheTags());
+    Cache::invalidateTags($this->view->storage->getCacheTagsToInvalidate());
   }
 
   /**

core/modules/views/src/Tests/Plugin/CacheTagTest.php

@@ -197,7 +197,7 @@ class CacheTagTest extends PluginTestBase {
     $view->destroy();
     // Invalidate the views cache tags in order to invalidate the render
     // caching.
-    \Drupal::service('cache_tags.invalidator')->invalidateTags($view->storage->getCacheTags());
+    \Drupal::service('cache_tags.invalidator')->invalidateTags($view->storage->getCacheTagsToInvalidate());
     $build = $view->buildRenderable();
     $renderer->renderPlain($build);
 

core/modules/views_ui/src/ViewUI.php

@@ -1336,4 +1336,32 @@ class ViewUI implements ViewEntityInterface {
     return $this->storage->hasTrustedData();
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function addCacheContexts(array $cache_contexts) {
+    return $this->storage->addCacheContexts($cache_contexts);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function mergeCacheMaxAge($max_age) {
+    return $this->storage->mergeCacheMaxAge($max_age);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheTagsToInvalidate() {
+    return $this->storage->getCacheTagsToInvalidate();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addCacheTags(array $cache_tags) {
+    return $this->storage->addCacheTags($cache_tags);
+  }
+
 }

core/tests/Drupal/Tests/Core/Entity/EntityUnitTest.php

@@ -8,6 +8,7 @@
 namespace Drupal\Tests\Core\Entity;
 
 use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Cache\Cache;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\Entity\Entity;
 use Drupal\Core\Entity\Exception\NoCorrespondingEntityClassException;
@@ -486,4 +487,58 @@ class EntityUnitTest extends UnitTestCase {
   public function testReferencedEntities() {
     $this->assertSame(array(), $this->entity->referencedEntities());
   }
+
+  /**
+   * @covers ::getCacheTags
+   * @covers ::getCacheTagsToInvalidate
+   * @covers ::addCacheTags
+   */
+  public function testCacheTags() {
+    // Ensure that both methods return the same by default.
+    $this->assertEquals([$this->entityTypeId . ':' . 1], $this->entity->getCacheTags());
+    $this->assertEquals([$this->entityTypeId . ':' . 1], $this->entity->getCacheTagsToInvalidate());
+
+    // Add an additional cache tag and make sure only getCacheTags() returns
+    // that.
+    $this->entity->addCacheTags(['additional_cache_tag']);
+
+    $this->assertEquals(['additional_cache_tag', $this->entityTypeId . ':' . 1], $this->entity->getCacheTags());
+    $this->assertEquals([$this->entityTypeId . ':' . 1], $this->entity->getCacheTagsToInvalidate());
+  }
+
+  /**
+   * @covers ::getCacheContexts
+   * @covers ::addCacheContexts
+   */
+  public function testCacheContexts() {
+    $cache_contexts_manager = $this->getMockBuilder('Drupal\Core\Cache\Context\CacheContextsManager')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $container = new ContainerBuilder();
+    $container->set('cache_contexts_manager', $cache_contexts_manager);
+    \Drupal::setContainer($container);
+
+    // There are no cache contexts by default.
+    $this->assertEquals([], $this->entity->getCacheContexts());
+
+    // Add an additional cache context.
+    $this->entity->addCacheContexts(['user']);
+    $this->assertEquals(['user'], $this->entity->getCacheContexts());
+  }
+
+  /**
+   * @covers ::getCacheMaxAge
+   * @covers ::mergeCacheMaxAge
+   */
+  public function testCacheMaxAge() {
+    // Cache max age is permanent by default.
+    $this->assertEquals(Cache::PERMANENT, $this->entity->getCacheMaxAge());
+
+    // Set two cache max ages, the lower value is the one that needs to be
+    // returned.
+    $this->entity->mergeCacheMaxAge(600);
+    $this->entity->mergeCacheMaxAge(1800);
+    $this->assertEquals(600, $this->entity->getCacheMaxAge());
+  }
+
 }