diff core/lib/Drupal/Core/Session/WriteSafeSessionHandler.php @ 18:af1871eacc83

Update to Drupal core 8.7.1

--- a/core/lib/Drupal/Core/Session/WriteSafeSessionHandler.php	Thu Feb 28 13:21:36 2019 +0000
+++ b/core/lib/Drupal/Core/Session/WriteSafeSessionHandler.php	Thu May 09 15:33:08 2019 +0100
@@ -3,7 +3,7 @@
 namespace Drupal\Core\Session;
 
 /**
- * Wraps another SessionHandlerInterface to prevent writes when not allowed.
+ * Wraps the session handler to prevent writes when not necessary or allowed.
  */
 class WriteSafeSessionHandler implements \SessionHandlerInterface, WriteSafeSessionHandlerInterface {
 
@@ -20,6 +20,14 @@
   protected $sessionWritable;
 
   /**
+   * The read sessions.
+   *
+   * @var array
+   *   Session data keyed by the session ID.
+   */
+  private $readSessions;
+
+  /**
    * Constructs a new write safe session handler.
    *
    * @param \SessionHandlerInterface $wrapped_session_handler
@@ -64,19 +72,23 @@
    * {@inheritdoc}
    */
   public function read($session_id) {
-    return $this->wrappedSessionHandler->read($session_id);
+    $value = $this->wrappedSessionHandler->read($session_id);
+    $this->readSessions[$session_id] = $value;
+    return $value;
   }
 
   /**
    * {@inheritdoc}
    */
   public function write($session_id, $session_data) {
+    // Only write the session when it has been modified.
+    if (isset($this->readSessions[$session_id]) && $this->readSessions[$session_id] === $session_data) {
+      return TRUE;
+    }
     if ($this->isSessionWritable()) {
       return $this->wrappedSessionHandler->write($session_id, $session_data);
     }
-    else {
-      return TRUE;
-    }
+    return TRUE;
   }
 
   /**