Custom validation rules

Use the public synchronous ValidationSchema.custom predicate for field-level HTTP validation. Return true for success, false or an error message for failure.

import assert from 'node:assert/strict';
import type { ValidationSchema } from '@tagna/udiot';

const code: ValidationSchema = {
  type: 'string',
  required: true,
  custom: value => /^[A-Z]{3}$/.test(value) || 'Use three uppercase letters',
};
assert.equal(code.custom?.('ABC'), true);
assert.equal(code.custom?.('abc'), 'Use three uppercase letters');

For forms, use a validationRules helper or an application-owned object with validate(value): boolean and message: string. Do not pass async callbacks to synchronous rules. Keep regular expressions bounded and reviewed for hostile input.

The internal natural-language parser, registerPattern and registerFieldPattern are not public registry extension points. Unknown natural-language text must not be used as a security validation rule.