Issue #3130751 by stefanos.petrakis, Medha Kumari, larowlan, alexpott, jungle: Fix LanguageNegotiationContentEntity::getLangcode() errors thrown

(cherry picked from commit 5738144ad9)

core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationContentEntity.php

@@ -90,6 +90,10 @@ class LanguageNegotiationContentEntity extends LanguageNegotiationMethodBase imp
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
+    if ($request === NULL || $this->languageManager === NULL) {
+      return NULL;
+    }
+
     $langcode = $request->query->get(static::QUERY_PARAMETER);
 
     $language_enabled = array_key_exists($langcode, $this->languageManager->getLanguages());

core/modules/language/tests/src/Unit/Plugin/LanguageNegotiation/LanguageNegotiationContentEntityTest.php

@@ -0,0 +1,116 @@
+<?php
+
+namespace Drupal\Tests\language\Unit\Plugin\LanguageNegotiation;
+
+use Symfony\Component\HttpFoundation\Request;
+use Drupal\Core\Cache\Context\CacheContextsManager;
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\Core\Entity\EntityTypeManager;
+use Drupal\Core\Language\LanguageInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\language\ConfigurableLanguageManagerInterface;
+use Drupal\Tests\UnitTestCase;
+use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationContentEntity;
+
+/**
+ * Tests the LanguageNegotiationContentEntity plugin class.
+ *
+ * @group language
+ * @coversDefaultClass \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationContentEntity
+ * @see \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationContentEntity
+ */
+class LanguageNegotiationContentEntityTest extends UnitTestCase {
+
+  /**
+   * An array of mock LanguageInterface objects.
+   *
+   * @var \Drupal\Core\Language\LanguageInterface
+   */
+  protected array $languages;
+
+  /**
+   * A mock LanguageManager object.
+   *
+   * @var \Drupal\language\ConfigurableLanguageManagerInterface
+   */
+  protected $languageManager;
+
+  /**
+   * A mock object implementing the AccountInterface.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $user;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+
+    // Set up some languages to be used by the language-based path processor.
+    $language_de = $this->createMock(LanguageInterface::class);
+    $language_de->expects($this->any())
+      ->method('getId')
+      ->will($this->returnValue('de'));
+    $language_en = $this->createMock(LanguageInterface::class);
+    $language_en->expects($this->any())
+      ->method('getId')
+      ->will($this->returnValue('en'));
+    $languages = [
+      'de' => $language_de,
+      'en' => $language_en,
+    ];
+    $this->languages = $languages;
+
+    $language_manager = $this->getMockBuilder(ConfigurableLanguageManagerInterface::class)
+      ->getMock();
+    $language_manager->expects($this->any())
+      ->method('getLanguages')
+      ->will($this->returnValue($languages));
+    $this->languageManager = $language_manager;
+
+    $this->user = $this->getMockBuilder(AccountInterface::class)
+      ->getMock();
+
+    $cache_contexts_manager = $this->getMockBuilder(CacheContextsManager::class)
+      ->disableOriginalConstructor()
+      ->getMock();
+    $cache_contexts_manager->method('assertValidTokens')->willReturn(TRUE);
+    $container = new ContainerBuilder();
+    $container->set('cache_contexts_manager', $cache_contexts_manager);
+    \Drupal::setContainer($container);
+  }
+
+  /**
+   * @covers ::getLangcode
+   */
+  public function testGetLangcode() {
+    $entityTypeManagerMock = $this->getMockBuilder(EntityTypeManager::class)
+      ->disableOriginalConstructor()
+      ->getMock();
+    $languageNegotiationContentEntity = new LanguageNegotiationContentEntity($entityTypeManagerMock);
+    $languageNegotiationContentEntity->setLanguageManager($this->languageManager);
+
+    // Case 1: NULL request object argument.
+    $this->assertSame(NULL, $languageNegotiationContentEntity->getLangcode());
+
+    // Case 2: A request object is available, but the languageManager is not
+    // set.
+    $request = Request::create('/foo', 'GET');
+    $this->assertSame(NULL, $languageNegotiationContentEntity->getLangcode($request));
+
+    // Case 3: A request object is available, but static::QUERY_PARAMETER is
+    // set to a non-enabled language.
+    $request = Request::create('/foo', 'GET',
+      [LanguageNegotiationContentEntity::QUERY_PARAMETER => 'it']);
+    $this->assertSame(NULL, $languageNegotiationContentEntity->getLangcode($request));
+
+    // Case 4: A request object is available and static::QUERY_PARAMETER is
+    // set to an enabled language.
+    $request = Request::create('/foo', 'GET',
+      [LanguageNegotiationContentEntity::QUERY_PARAMETER => 'de']);
+    $this->assertSame('de', $languageNegotiationContentEntity->getLangcode($request));
+
+  }
+
+}