ConfigManager::diff

public ConfigManager::diff(StorageInterface $source_storage, StorageInterface $target_storage, $source_name, $target_name = NULL, $collection = StorageInterface::DEFAULT_COLLECTION)

public function diff(StorageInterface $source_storage, StorageInterface $target_storage, $source_name, $target_name = NULL, $collection = StorageInterface::DEFAULT_COLLECTION) {
  if ($collection != StorageInterface::DEFAULT_COLLECTION) {
    $source_storage = $source_storage->createCollection($collection);
    $target_storage = $target_storage->createCollection($collection);
  }
  if (!isset($target_name)) {
    $target_name = $source_name;
  }
  // The output should show configuration object differences formatted as YAML.
  // But the configuration is not necessarily stored in files. Therefore, they
  // need to be read and parsed, and lastly, dumped into YAML strings.
  $source_data = explode("\n", Yaml::encode($source_storage->read($source_name)));
  $target_data = explode("\n", Yaml::encode($target_storage->read($target_name)));

  // Check for new or removed files.
  if ($source_data === array('false')) {
    // Added file.
    // Cast the result of t() to a string, as the diff engine doesn't know
    // about objects.
    $source_data = array((string) $this->t('File added'));
  }
  if ($target_data === array('false')) {
    // Deleted file.
    // Cast the result of t() to a string, as the diff engine doesn't know
    // about objects.
    $target_data = array((string) $this->t('File removed'));
  }

  return new Diff($source_data, $target_data);
}