Issue #1899994 by katbailey, plach, YesCT: Fixed Disentangle language...

Issue #1899994 by katbailey, plach, YesCT: Fixed Disentangle language initialization from path resolution.

core/lib/Drupal/Core/EventSubscriber/PathSubscriber.php

@@ -81,10 +81,13 @@ public function onKernelRequestFrontPageResolve(GetResponseEvent $event) {
    *   The Event to process.
    */
   public function onKernelRequestLanguageResolve(GetResponseEvent $event) {
-    $request = $event->getRequest();
+    // We need to act only on the master request, otherwise subrequests will
+    // inherit the main request path and an infinite loop will be started.
+    if ($event->getRequestType() == HttpKernelInterface::MASTER_REQUEST) {
       $path = _language_resolved_path();
       if ($path !== NULL) {
-      $this->setPath($request, $path);
+        $this->setPath($event->getRequest(), $path);
+      }
     }
   }
 

core/modules/language/lib/Drupal/language/Tests/LanguageUrlRewritingTest.php

@@ -19,7 +19,7 @@ class LanguageUrlRewritingTest extends WebTestBase {
    *
    * @var array
    */
-  public static $modules = array('language');
+  public static $modules = array('language', 'language_test');
 
   public static function getInfo() {
     return array(
@@ -59,6 +59,10 @@ function testUrlRewritingEdgeCases() {
     $non_existing = language_default();
     $non_existing->langcode = $this->randomName();
     $this->checkUrl($non_existing, 'Path language is ignored if language is not installed.', 'URL language negotiation does not work with non-installed languages');
+
+    // Check that URL rewriting is not applied to subrequests.
+    $this->drupalGet('language_test/subrequest');
+    $this->assertText($this->web_user->name, 'Page correctly retrieved');
   }
 
   /**

core/modules/language/tests/language_test/language_test.module

@@ -5,6 +5,9 @@
  * Mock module for language layer tests.
  */
 
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpKernel\HttpKernelInterface;
+
 /**
  * Implements hook_init().
  */
@@ -94,3 +97,25 @@ function language_test_store_language_negotiation() {
 function language_test_language_negotiation_method($languages) {
   return 'it';
 }
+
+/**
+ * Implements hook_menu().
+ */
+function language_test_menu() {
+  $items = array();
+
+  $items['language_test/subrequest'] = array(
+    'page callback' => 'language_test_subrequest',
+    'access callback' => TRUE,
+    'type' => MENU_CALLBACK,
+  );
+
+  return $items;
+}
+
+/**
+ * Page callback. Uses a subrequest to retrieve the 'user' page.
+ */
+function language_test_subrequest() {
+  return drupal_container()->get('http_kernel')->handle(Request::create('/user'), HttpKernelInterface::SUB_REQUEST);
+}