When creating a decorator using class-validator how do I set a default error message?

Question

If the user using my decorator does not define "message" in validationOptions my constraint is reported with an empty string ''.

export function IsISO6391(validationOptions?: ValidationOptions) {
  return function (object: Object, propertyName: string) {
    registerDecorator({
      name: 'IsISO6391',
      target: object.constructor,
      propertyName: propertyName,
      constraints: [],
      options: validationOptions,
      validator: {
        validate,
      }
    });
  };
}

How do I set a default error message?

Answer 1

Found a way to do it:

export function IsISO6391(validationOptions?: ValidationOptions) {
  return function (object: Object, propertyName: string) {
    registerDecorator({
      name: 'IsISO6391',
      target: object.constructor,
      propertyName: propertyName,
      constraints: [],
      options: validationOptions,
      validator: {
        validate,
        defaultMessage(args: ValidationArguments) {
          return `${args.property} is not a valid ISO639-1 language code`;
        },
      },
    });
  };
}