Issue #2684873 by alexpott, dawehner, Xano: ConfigurableLanguageManager::getConfigOverrideLanguage() returns NULL

core/modules/language/language.services.yml

@@ -14,7 +14,7 @@ services:
       - { name: event_subscriber }
   language.config_factory_override:
     class: Drupal\language\Config\LanguageConfigFactoryOverride
-    arguments: ['@config.storage', '@event_dispatcher', '@config.typed']
+    arguments: ['@config.storage', '@event_dispatcher', '@config.typed', '@language.default']
     tags:
       - { name: config.factory.override, priority: -254 }
       - { name: event_subscriber }

core/modules/language/src/Config/LanguageConfigFactoryOverride.php

@@ -68,11 +68,16 @@ class LanguageConfigFactoryOverride extends ConfigFactoryOverrideBase implements
    *   An event dispatcher instance to use for configuration events.
    * @param \Drupal\Core\Config\TypedConfigManagerInterface $typed_config
    *   The typed configuration manager.
+   * @param \Drupal\Core\Language\LanguageDefault $default_language
+   *   The default language.
    */
-  public function __construct(StorageInterface $storage, EventDispatcherInterface $event_dispatcher, TypedConfigManagerInterface $typed_config) {
+  public function __construct(StorageInterface $storage, EventDispatcherInterface $event_dispatcher, TypedConfigManagerInterface $typed_config, LanguageDefault $default_language) {
     $this->baseStorage = $storage;
     $this->eventDispatcher = $event_dispatcher;
     $this->typedConfigManager = $typed_config;
+    // Prior to negiotiation the override language should be the default
+    // language.
+    $this->language = $default_language->get();
   }
 
   /**

core/modules/language/src/Config/LanguageConfigFactoryOverrideInterface.php

@@ -36,6 +36,10 @@ interface LanguageConfigFactoryOverrideInterface extends ConfigFactoryOverrideIn
    *   The default language.
    *
    * @return $this
+   *
+   * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This
+   *   method has been replaced by injecting the default language into the
+   *   constructor.
    */
   public function setLanguageFromDefault(LanguageDefault $language_default = NULL);
 

core/modules/language/src/LanguageServiceProvider.php

@@ -54,13 +54,6 @@ class LanguageServiceProvider extends ServiceProviderBase {
       $container->setParameter('language.default_values', $default_language_values);
     }
 
-    // For monolingual sites, we explicitly set the default language for the
-    // language config override service as there is no language negotiation.
-    if (!$this->isMultilingual()) {
-      $container->getDefinition('language.config_factory_override')
-        ->addMethodCall('setLanguageFromDefault', array(new Reference('language.default')));
-    }
-
   }
 
   /**

core/modules/language/tests/src/Kernel/LanguageConfigFactoryOverrideTest.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace Drupal\Tests\language\Kernel;
+
+use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests \Drupal\language\Config\LanguageConfigFactoryOverride.
+ *
+ * @group language
+ */
+class LanguageConfigFactoryOverrideTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('system', 'language');
+
+  /**
+   * Tests language.config_factory_override service has the default language.
+   */
+  public function testLanguageConfigFactoryOverride() {
+    $this->installConfig('system');
+    $this->installConfig('language');
+
+    /** @var \Drupal\language\Config\LanguageConfigFactoryOverride $config_factory_override */
+    $config_factory_override = \Drupal::service('language.config_factory_override');
+    $this->assertEquals('en', $config_factory_override->getLanguage()->getId());
+
+    ConfigurableLanguage::createFromLangcode('de')->save();
+
+    // Invalidate the container.
+    $this->config('system.site')->set('default_langcode', 'de')->save();
+    drupal_flush_all_caches();
+
+    $config_factory_override = \Drupal::service('language.config_factory_override');
+    $this->assertEquals('de', $config_factory_override->getLanguage()->getId());
+  }
+
+}