safeRelativeAssetPath function

String safeRelativeAssetPath(String uri)

A reference inside a model is always relative to the model. An absolute path or a .. segment means the file is reaching outside its directory, which is worth refusing rather than resolving.

Public because the sources that need it are in another package now, and a second copy of this check is a second chance to get it wrong.

Implementation

String safeRelativeAssetPath(String uri) {
  final relative = Uri.decodeComponent(uri);
  if (relative.startsWith('/') ||
      relative.startsWith(r'\') ||
      relative.contains('://') ||
      relative.split(RegExp(r'[/\\]')).contains('..')) {
    throw ArgumentError(
      'Refusing to load "$uri": it escapes the asset directory.',
    );
  }
  return relative;
}