protected function pointer(string $path, ?string $member = null): array
    {
        /** Member can be '0' which is an empty string. */
        $withoutMember = is_null($member) || '' === $member;
        $pointer = !$withoutMember ? sprintf('%s/%s', rtrim($path, '/'), $member) : $path;

        return [Error::SOURCE_POINTER => $pointer];
    }