followSkillPointer function

Future<SkillPointerFollow> followSkillPointer(String path, Future<String?> readPointer(String pointerPath))

Reads the <path>.pointer sibling of path through readPointer and classifies it. readPointer returns null when the file does not exist.

The security invariant (gh-1444): only builtin://skills/<name>/SKILL.md targets naming a compiled-in skill whose name matches the directory of path resolve; everything else is SkillPointerRefused.

Implementation

Future<SkillPointerFollow> followSkillPointer(
  String path,
  Future<String?> Function(String pointerPath) readPointer,
) async {
  String? content;
  try {
    content = await readPointer('$path.pointer');
  } on Object {
    return const SkillPointerAbsent();
  }
  if (content == null) return const SkillPointerAbsent();
  final reason = validateSkillPointerTarget(path, content);
  if (reason != null) return SkillPointerRefused(reason);
  final target = skillPointerTarget(content)!;
  final text = builtinSkillTextAt(target);
  if (text == null) {
    return SkillPointerRefused(
      'pointer target $target is not a compiled-in builtin skill',
    );
  }
  return SkillPointerResolved(text, targetSkillName(target)!);
}