Function RandomStringByRegex

tools/security/random_by_regex.go:27–50

RandomStringByRegex generates a random string matching the regex pattern. If optFlags is not set, fallbacks to [syntax.Perl]. NB! While the source of the randomness comes from [crypto/rand] this method is not recommended to be used on its own in critical secure contexts because the generated length

(pattern string, optFlags ...syntax.Flags)

//
// This function is inspired by github.com/pipe01/revregexp, github.com/lucasjones/reggen and other similar packages.
func RandomStringByRegex(pattern string, optFlags ...syntax.Flags) (string, error) {
	var flags syntax.Flags
	if len(optFlags) == 0 {
		flags = syntax.Perl
	} else {
		for _, f := range optFlags {
			flags |= f
		}
	}

	r, err := syntax.Parse(pattern, flags)
	if err != nil {
		return "", err
	}

	var sb = new(strings.Builder)

	err = writeRandomStringByRegex(r, sb)
	if err != nil {
		return "", err
	}

	return sb.String(), nil
}

func writeRandomStringByRegex(r *syntax.Regexp, sb *strings.Builder) error {
	// https://pkg.go.dev/regexp/syntax#Op