Update to Drupal 8.0.0 beta 14. For more information, see https://drupal.org/node/2544542

core/modules/forum/forum.module

@@ -540,7 +540,7 @@ function template_preprocess_forum_list(&$variables) {
   $row = 0;
   // Sanitize each forum so that the template can safely print the data.
   foreach ($variables['forums'] as $id => $forum) {
-    $variables['forums'][$id]->description = Xss::filterAdmin($forum->description->value);
+    $variables['forums'][$id]->description = array('#markup' => $forum->description->value);
     $variables['forums'][$id]->link = forum_uri($forum);
     $variables['forums'][$id]->name = SafeMarkup::checkPlain($forum->label());
     $variables['forums'][$id]->is_container = !empty($forum->forum_container->value);

core/modules/forum/migration_templates/d6_forum_settings.yml

@@ -0,0 +1,29 @@
+id: d6_forum_settings
+label: Drupal 6 forum configuration
+migration_tags:
+  - Drupal 6
+source:
+  plugin: variable
+  variables:
+    - forum_hot_topic
+    - forum_per_page
+    - forum_order
+    - forum_block_num_0
+    - forum_block_num_1
+    - forum_nav_vocabulary
+process:
+  'block/active/limit': forum_block_num_0
+  'block/new/limit': forum_block_num_1
+  'topics/hot_threshold': forum_hot_topic
+  'topics/page_limit': forum_per_page
+  'topics/order': forum_order
+  vocabulary:
+    plugin: migration
+    migration: d6_taxonomy_vocabulary
+    source: forum_nav_vocabulary
+destination:
+  plugin: config
+  config_name: forum.settings
+migration_dependencies:
+  required:
+    - d6_taxonomy_vocabulary

core/modules/forum/src/Form/Overview.php

@@ -86,9 +86,7 @@ class Overview extends OverviewTerms {
     // Remove the alphabetical reset.
     unset($form['actions']['reset_alphabetical']);
 
-    // The form needs to have submit and validate handlers set explicitly.
     // Use the existing taxonomy overview submit handler.
-    $form['#submit'] = array('::submitForm');
     $form['terms']['#empty'] = $this->t('No containers or forums available. <a href="@container">Add container</a> or <a href="@forum">Add forum</a>.', array(
       '@container' => $this->url('forum.add_container'),
       '@forum' => $this->url('forum.add_forum')

core/modules/forum/src/ProxyClass/ForumUninstallValidator.php

@@ -0,0 +1,92 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\forum\ProxyClass\ForumUninstallValidator.
+ */
+
+/**
+ * This file was generated via php core/scripts/generate-proxy-class.php 'Drupal\forum\ForumUninstallValidator' "core/modules/forum/src".
+ */
+
+namespace Drupal\forum\ProxyClass {
+
+    /**
+     * Provides a proxy class for \Drupal\forum\ForumUninstallValidator.
+     *
+     * @see \Drupal\Component\ProxyBuilder
+     */
+    class ForumUninstallValidator implements \Drupal\Core\Extension\ModuleUninstallValidatorInterface
+    {
+
+        use \Drupal\Core\DependencyInjection\DependencySerializationTrait;
+
+        /**
+         * The id of the original proxied service.
+         *
+         * @var string
+         */
+        protected $drupalProxyOriginalServiceId;
+
+        /**
+         * The real proxied service, after it was lazy loaded.
+         *
+         * @var \Drupal\forum\ForumUninstallValidator
+         */
+        protected $service;
+
+        /**
+         * The service container.
+         *
+         * @var \Symfony\Component\DependencyInjection\ContainerInterface
+         */
+        protected $container;
+
+        /**
+         * Constructs a ProxyClass Drupal proxy object.
+         *
+         * @param \Symfony\Component\DependencyInjection\ContainerInterface $container
+         *   The container.
+         * @param string $drupal_proxy_original_service_id
+         *   The service ID of the original service.
+         */
+        public function __construct(\Symfony\Component\DependencyInjection\ContainerInterface $container, $drupal_proxy_original_service_id)
+        {
+            $this->container = $container;
+            $this->drupalProxyOriginalServiceId = $drupal_proxy_original_service_id;
+        }
+
+        /**
+         * Lazy loads the real service from the container.
+         *
+         * @return object
+         *   Returns the constructed real service.
+         */
+        protected function lazyLoadItself()
+        {
+            if (!isset($this->service)) {
+                $this->service = $this->container->get($this->drupalProxyOriginalServiceId);
+            }
+
+            return $this->service;
+        }
+
+        /**
+         * {@inheritdoc}
+         */
+        public function validate($module)
+        {
+            return $this->lazyLoadItself()->validate($module);
+        }
+
+        /**
+         * {@inheritdoc}
+         */
+        public function setStringTranslation(\Drupal\Core\StringTranslation\TranslationInterface $translation)
+        {
+            return $this->lazyLoadItself()->setStringTranslation($translation);
+        }
+
+    }
+
+}

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

@@ -0,0 +1,59 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\forum\Tests\Migrate\d6\MigrateForumConfigsTest.
+ */
+
+namespace Drupal\forum\Tests\Migrate\d6;
+
+use Drupal\config\Tests\SchemaCheckTestTrait;
+use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
+
+/**
+ * Upgrade variables to forum.settings.yml.
+ *
+ * @group forum
+ */
+class MigrateForumConfigsTest extends MigrateDrupal6TestBase {
+
+  use SchemaCheckTestTrait;
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('comment', 'forum', 'taxonomy');
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->prepareMigrations(array(
+      'd6_taxonomy_vocabulary' => array(
+        array(array(1), array('vocabulary_1_i_0_')),
+      )
+    ));
+    $this->loadDumps(['Variable.php']);
+    $this->executeMigration('d6_forum_settings');
+  }
+
+  /**
+   * Tests migration of forum variables to forum.settings.yml.
+   */
+  public function testForumSettings() {
+    $config = $this->config('forum.settings');
+    $this->assertIdentical(15, $config->get('topics.hot_threshold'));
+    $this->assertIdentical(25, $config->get('topics.page_limit'));
+    $this->assertIdentical(1, $config->get('topics.order'));
+    $this->assertIdentical('vocabulary_1_i_0_', $config->get('vocabulary'));
+    // This is 'forum_block_num_0' in D6, but block:active:limit' in D8.
+    $this->assertIdentical(5, $config->get('block.active.limit'));
+    // This is 'forum_block_num_1' in D6, but 'block:new:limit' in D8.
+    $this->assertIdentical(5, $config->get('block.new.limit'));
+    $this->assertConfigSchema(\Drupal::service('config.typed'), 'forum.settings', $config->get());
+  }
+
+}