Implements \Drupal\Core\Path\AliasManagerInterface::getSystemPath().
Overrides AliasManagerInterface::getSystemPath
public function getSystemPath($path, $path_language = NULL) {
  // If no language is explicitly specified we default to the current URL
  // language. If we used a language different from the one conveyed by the
  // requested URL, we might end up being unable to check if there is a path
  // alias matching the URL path.
  $path_language = $path_language ?: $this->langcode;
  $original_path = $path;
  // Lookup the path alias first.
  if (!empty($path) && ($source = $this
    ->lookupPathSource($path, $path_language))) {
    $path = $source;
  }
  return $path;
}