Issue #3343859 Session storage methods should not rely on cache

src/Session/SessionStorage.php

@@ -88,10 +88,10 @@ class SessionStorage implements SessionStorageInterface {
   public function exists(
     string $id = SessionInterface::SESSION_ID_DEFAULT
   ): bool {
-    // Creating/deleting sessions should always happen through the interface
-    // provided by this storage. We therefore do not need to actually load the
-    // session from the storage.
-    return isset($this->cache[$id]);
+    // We don't check existing in the cache because we load sessions as
+    // requested. There may therefore exist sessions in the store that do not
+    // yet exist in the cache.
+    return $this->store->has($id);
   }
 
   /**
@@ -106,10 +106,10 @@ class SessionStorage implements SessionStorageInterface {
    * {@inheritdoc}
    */
   public function getCount(): int {
-    // Creating/deleting sessions should always happen through the interface
-    // provided by this storage. We therefore do not need to actually load the
-    // sessions from the storage.
-    return count(array_filter($this->cache));
+    // We don't get the count from the cache because we load sessions as
+    // requested. There may therefore exist sessions in the store that do not
+    // yet exist in the cache.
+    return count($this->store->getAll());
   }
 
   /**