Clarifying the _current_path() problem as it relates to path alias caching and...

Clarifying the _current_path() problem as it relates to path alias caching and making the request param non-optional in language_from_url

core/includes/path.inc

@@ -214,18 +214,16 @@ function drupal_cache_system_paths() {
   $cache = &drupal_static('drupal_lookup_path', array());
   if (empty($cache['system_paths']) && !empty($cache['map'])) {
 
-    // @todo Because caching happens during $kernel->terminate(), i.e.
-    // after we have left the scope of the Request, the call to current_path()
-    // here does not return the system path, and instead calls out to
-    // _current_path(), which returns the alias. So the alias gets used as the
-    // key instead. At lookup time, whether the alias or the source is used as
-    // the key depends on when the first call to url() is made for that path.
-    // If this is within the request scope, it uses the system_path and so will
-    // be a cache miss. There is a separate issue for fixing up the path alias
-    // logic here: http://drupal.org/node/1269742
+    // @todo Because we are not within the request scope at this time, we cannot
+    //   use current_path(), which would give us the system path to use as the
+    //   key. Instead we call _current_path(), which may give us the alias
+    //   instead. However, at lookup time the system path will be used as the
+    //   key, because it uses current_path(), and so it will be a cache miss.
+    //   There is a critical issue for fixing the path alias logic here:
+    //   http://drupal.org/node/1269742
 
     // Generate a cache ID (cid) specifically for this page.
-    $cid = current_path();
+    $cid = _current_path();
     // The static $map array used by drupal_lookup_path() includes all
     // system paths for the page request.
     if ($paths = current($cache['map'])) {
@@ -369,11 +367,14 @@ function drupal_match_path($path, $patterns) {
  * @see request_path()
  */
 function current_path() {
+  // @todo Remove the check for whether the request service exists and the
+  // fallback code below, once the path alias logic has been figured out in
+  // http://drupal.org/node/1269742.
   if (drupal_container()->has('request')) {
     return drupal_container()->get('request')->attributes->get('system_path');
   }
-  // If we are outside the request scope, e.g. during $kernel->terminate, fall
-  // back to using the path stored in _current_path().
+  // If we are outside the request scope, fall back to using the path stored in
+  // _current_path().
   return _current_path();
 }
 

core/modules/language/language.negotiation.inc

@@ -197,10 +197,13 @@ function language_from_session($languages) {
  * @param $languages
  *   An array of valid language objects.
  *
+ * @param $request
+ *   The HttpRequest object representing the current request.
+ *
  * @return
  *   A valid language code on success, FALSE otherwise.
  */
-function language_from_url($languages, $request = NULL) {
+function language_from_url($languages, $request) {
   $language_url = FALSE;
 
   if (!language_negotiation_method_enabled(LANGUAGE_NEGOTIATION_URL)) {
@@ -209,23 +212,17 @@ function language_from_url($languages, $request = NULL) {
 
   switch (variable_get('language_negotiation_url_part', LANGUAGE_NEGOTIATION_URL_PREFIX)) {
     case LANGUAGE_NEGOTIATION_URL_PREFIX:
-      // Language negotiation happens before the public function current_path()
-      // is available.
-      // @todo Refactor with Symfony's Request object.
-      if ($request) {
-        $current_path = $request->attributes->get('system_path');
-        if (!isset($current_path)) {
-          $current_path = trim($request->getPathInfo(), '/');
-        }
-      }
-      else {
-        $current_path = _current_path();
+
+      $current_path = $request->attributes->get('system_path');
+      if (!isset($current_path)) {
+        $current_path = trim($request->getPathInfo(), '/');
       }
 
       list($language, $path) = language_url_split_prefix($current_path, $languages);
-      if ($request) {
-        $request->attributes->set('system_path', $path);
-      }
+      // Store the correct system path, i.e. minus the path prefix, in the
+      // request.
+      $request->attributes->set('system_path', $path);
+
       if ($language !== FALSE) {
         $language_url = $language->langcode;
       }