Getting all errors from field AND subfield

function allErrorsOfFieldAndSubfield(
  fields: Record<
    string,
    {
      errors: ValidationError[];
    }
  >,
  namespace: string,
) {
  return Object.entries(fields).reduce<ValidationError[]>((errors, [name, field]) => {
    if (!name.startsWith(namespace)) {
      return errors;
    }
    errors.push(...field.errors);
    return errors;
  }, []);
}

// usage
const errors = allErrorsOfFieldAndSubfield(form.getAllErrors().fields, 'parentKey');