veto

Schema validation package for fuf projects.

Install

pnpm add @fuf-stack/veto

Quick Start

import v, { object, string } from '@fuf-stack/veto';

const schema = {
  user: object({
    name: string(),
  }),
};

const result = v(schema).validate({
  user: { name: 'Ada' },
});

Deep Partial

Use deepPartial(schema) for schema-backed override configs where every nested field should become optional while scalar validation still applies when a value is provided.

import { deepPartial, object, string } from '@fuf-stack/veto';

const overrides = deepPartial(
  object({
    theme: object({
      color: string(),
    }),
  }),
);

overrides.parse({ theme: {} });

deepPartial supports objects, arrays, tuples, records, optional/nullable wrappers, default/catch/readonly/lazy wrappers, unions, discriminated unions, and intersections. For discriminated unions, the discriminator remains required so the matching branch can still be selected.

Arrays stay arrays: object elements become partial, while scalar elements keep their scalar type (string[] stays string[], not (string | undefined)[]).