Update to Drupal 8.0.0-beta15. For more information, see: https://www.drupal.org/node/2563023

core/modules/forum/src/Breadcrumb/ForumBreadcrumbBuilderBase.php

@@ -8,6 +8,7 @@
 namespace Drupal\forum\Breadcrumb;
 
 use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
+use Drupal\Core\Breadcrumb\Breadcrumb;
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Link;
@@ -65,14 +66,18 @@ abstract class ForumBreadcrumbBuilderBase  implements BreadcrumbBuilderInterface
    * {@inheritdoc}
    */
   public function build(RouteMatchInterface $route_match) {
-    $breadcrumb[] = Link::createFromRoute($this->t('Home'), '<front>');
+    $breadcrumb = new Breadcrumb();
+    $breadcrumb->setCacheContexts(['route']);
+
+    $links[] = Link::createFromRoute($this->t('Home'), '<front>');
 
     $vocabulary = $this->entityManager
       ->getStorage('taxonomy_vocabulary')
       ->load($this->config->get('vocabulary'));
-    $breadcrumb[] = Link::createFromRoute($vocabulary->label(), 'forum.index');
+    $breadcrumb->addCacheableDependency($vocabulary);
+    $links[] = Link::createFromRoute($vocabulary->label(), 'forum.index');
 
-    return $breadcrumb;
+    return $breadcrumb->setLinks($links);
   }
 
 }

core/modules/forum/src/Breadcrumb/ForumListingBreadcrumbBuilder.php

@@ -27,19 +27,26 @@ class ForumListingBreadcrumbBuilder extends ForumBreadcrumbBuilderBase {
    */
   public function build(RouteMatchInterface $route_match) {
     $breadcrumb = parent::build($route_match);
+    $breadcrumb->addCacheContexts(['route']);
 
     // Add all parent forums to breadcrumbs.
-    $term_id = $route_match->getParameter('taxonomy_term')->id();
+    /** @var \Drupal\Taxonomy\TermInterface $term */
+    $term = $route_match->getParameter('taxonomy_term');
+    $term_id = $term->id();
+    $breadcrumb->addCacheableDependency($term);
+
     $parents = $this->forumManager->getParents($term_id);
     if ($parents) {
       foreach (array_reverse($parents) as $parent) {
         if ($parent->id() != $term_id) {
-          $breadcrumb[] = Link::createFromRoute($parent->label(), 'forum.page', array(
+          $breadcrumb->addCacheableDependency($parent);
+          $breadcrumb->addLink(Link::createFromRoute($parent->label(), 'forum.page', [
             'taxonomy_term' => $parent->id(),
-          ));
+          ]));
         }
       }
     }
+
     return $breadcrumb;
   }
 

core/modules/forum/src/Breadcrumb/ForumNodeBreadcrumbBuilder.php

@@ -29,18 +29,21 @@ class ForumNodeBreadcrumbBuilder extends ForumBreadcrumbBuilderBase {
    */
   public function build(RouteMatchInterface $route_match) {
     $breadcrumb = parent::build($route_match);
+    $breadcrumb->addCacheContexts(['route']);
 
     $parents = $this->forumManager->getParents($route_match->getParameter('node')->forum_tid);
     if ($parents) {
       $parents = array_reverse($parents);
       foreach ($parents as $parent) {
-        $breadcrumb[] = Link::createFromRoute($parent->label(), 'forum.page',
+        $breadcrumb->addCacheableDependency($parent);
+        $breadcrumb->addLink(Link::createFromRoute($parent->label(), 'forum.page',
           array(
             'taxonomy_term' => $parent->id(),
           )
-        );
+        ));
       }
     }
+
     return $breadcrumb;
   }
 

core/modules/forum/src/Controller/ForumController.php

@@ -190,6 +190,7 @@ class ForumController extends ControllerBase {
     else {
       // Set the page title to forum's vocabulary name.
       $build['#title'] = $vocabulary->label();
+      $this->renderer->addCacheableDependency($build, $vocabulary);
     }
     return $build;
   }

core/modules/forum/src/Tests/ForumTest.php

@@ -115,6 +115,7 @@ class ForumTest extends WebTestBase {
       'access comments',
     ));
     $this->drupalPlaceBlock('help_block', array('region' => 'help'));
+    $this->drupalPlaceBlock('local_actions_block');
   }
 
   /**
@@ -235,6 +236,7 @@ class ForumTest extends WebTestBase {
 
     // Test the root forum page title change.
     $this->drupalGet('forum');
+    $this->assertCacheTag('config:taxonomy.vocabulary.' . $this->forum['vid']);
     $this->assertTitle(t('Forums | Drupal'));
     $vocabulary = Vocabulary::load($this->forum['vid']);
     $vocabulary->set('name', 'Discussions');

core/modules/forum/src/Tests/Migrate/d6/MigrateForumConfigsTest.php

@@ -13,7 +13,7 @@ use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 /**
  * Upgrade variables to forum.settings.yml.
  *
- * @group forum
+ * @group migrate_drupal_6
  */
 class MigrateForumConfigsTest extends MigrateDrupal6TestBase {
 
@@ -36,7 +36,6 @@ class MigrateForumConfigsTest extends MigrateDrupal6TestBase {
         array(array(1), array('vocabulary_1_i_0_')),
       )
     ));
-    $this->loadDumps(['Variable.php']);
     $this->executeMigration('d6_forum_settings');
   }