Issue #2689607 by morenstrat, Ante890: Language from URL negotiator does not...

Issue #2689607 by morenstrat, Ante890: Language from URL negotiator does not add request query to language switcher links

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

@@ -192,6 +192,7 @@ public function processOutbound($path, &$options = array(), Request $request = N
    */
   public function getLanguageSwitchLinks(Request $request, $type, Url $url) {
     $links = array();
+    $query = $request->query->all();
 
     foreach ($this->languageManager->getNativeLanguages() as $language) {
       $links[$language->getId()] = array(
@@ -202,6 +203,7 @@ public function getLanguageSwitchLinks(Request $request, $type, Url $url) {
         'title' => $language->getName(),
         'language' => $language,
         'attributes' => array('class' => array('language-link')),
+        'query' => $query,
       );
     }
 

core/modules/language/src/Tests/LanguageSwitchingTest.php

@@ -118,8 +118,9 @@ protected function doTestLanguageBlockAuthenticated($block_label) {
   protected function doTestLanguageBlockAnonymous($block_label) {
     $this->drupalLogout();
 
-    // Assert that the language switching block is displayed on the frontpage.
-    $this->drupalGet('');
+    // Assert that the language switching block is displayed on the frontpage
+    // and ensure that the active class is added when query params are present.
+    $this->drupalGet('', ['query' => ['foo' => 'bar']]);
     $this->assertText($block_label, 'Language switcher block found.');
 
     // Assert that only the current language is marked as active.