Issue #2170117 by webflo: CMI FileStorage fails with absolute paths.

core/lib/Drupal/Core/Config/FileStorage.php

@@ -208,7 +208,7 @@ public function listAll($prefix = '') {
       throw new StorageException($this->directory . '/ not found.');
     }
     $extension = '.' . static::getFileExtension();
-    $files = new \GlobIterator(DRUPAL_ROOT . '/' . $this->directory . '/' . $prefix . '*' . $extension);
+    $files = new \GlobIterator($this->directory . '/' . $prefix . '*' . $extension);
 
     $names = array();
     foreach ($files as $file) {

core/modules/config/lib/Drupal/config/Tests/Storage/FileStorageTest.php

@@ -47,4 +47,24 @@ protected function update($name, $data) {
   protected function delete($name) {
     unlink($this->storage->getFilePath($name));
   }
+
+  /**
+   * Tests the FileStorage::listAll method with a relative and absolute path.
+   */
+  protected function testlistAll() {
+    $expected_files = array(
+      'system.module',
+      'system.performance',
+    );
+
+    $config_files = $this->storage->listAll();
+    $this->assertIdentical($config_files, $expected_files, 'Relative path, two config files found.');
+
+    // Initialize FileStorage with absolute file path.
+    $absolute_path = realpath($this->configDirectories[CONFIG_ACTIVE_DIRECTORY]);
+    $storage_absolute_path = new FileStorage($absolute_path);
+    $config_files = $storage_absolute_path->listAll();
+    $this->assertIdentical($config_files, $expected_files, 'Absolute path, two config files found.');
+  }
+
 }