createAliasResolver function

ResolveActions createAliasResolver(Map<String, Object> aliases, { String anyActionName = anyAction, bool validate = true, })

Builds a resolver from a map of alias to what it means.

final resolve = createAliasResolver({
  'modify': ['update', 'delete'],
  'access': ['read', 'modify'],
});

An alias may point at another alias, and the chain is followed. access above resolves to read, update, delete — so can('access', 'Article') grants a delete check.

Why this validates so aggressively

Both mistakes it catches produce an ability that is wrong rather than one that fails. A cycle would loop forever or silently truncate; aliasing the wildcard action would make one alias quietly grant everything. Neither is visible in a passing test that happens not to use the alias.

anyActionName is the action that already means "everything" — manage by default, and it must match the ability's.

Implementation

ResolveActions createAliasResolver(
  Map<String, Object> aliases, {
  String anyActionName = anyAction,
  bool validate = true,
}) {
  final expanded = <String, List<String>>{
    for (final entry in aliases.entries)
      entry.key: switch (entry.value) {
        final String single => [single],
        final Iterable<Object?> many => many.cast<String>().toList(),
        _ => throw ArgumentError.value(
          entry.value,
          entry.key,
          'an alias must map to a String or a List<String>',
        ),
      },
  };

  if (validate) {
    if (expanded.containsKey(anyActionName)) {
      throw ArgumentError.value(
        anyActionName,
        'aliases',
        'cannot alias "$anyActionName" because it already means every action',
      );
    }
    for (final name in expanded.keys) {
      _walk(expanded, [name], anyActionName, {name});
    }
  }

  return (actions) {
    final result = <String>[];
    final seen = <String>{};
    void add(String action) {
      if (!seen.add(action)) return;
      result.add(action);
      (expanded[action] ?? const <String>[]).forEach(add);
    }

    actions.forEach(add);
    return result;
  };
}