@vielzeug/spell

Zero-dependency schema validation library with strict-by-default objects, unified sync/async validate(), coercion, flexible schema composition, and full TypeScript inference.

Package: @vielzeug/spell  ·  Category: Validation

Key exports: s, SpellValidationError, setMessages, setLogger, resetMessages, ErrorCode, errorsAt, descriptorToJsonSchema

When to use: Zero-dependency schema validation library with strict-by-default objects, async refinements, coercion, flexible schema composition, and full TypeScript inference.

Related: @vielzeug/forge · @vielzeug/courier · @vielzeug/vault

@vielzeug/spell is part of Vielzeug and ships as a zero-dependency TypeScript package with ESM+CJS output.

Installation

pnpm add @vielzeug/spell
npm install @vielzeug/spell
yarn add @vielzeug/spell

Quick Start

import { s, type Infer } from '@vielzeug/spell';

const UserSchema = s.object({
  id: s.coerce.number().int().positive(),
  name: s.string().trim().min(1),
  email: s.string().trim().email(),
  role: s.union('admin', 'editor', 'viewer').default('viewer'),
  tags: s.array(s.string()).unique().default([]),
});

type User = Infer<typeof UserSchema>;

const result = UserSchema.safeParse({ id: '42', name: 'Ada', email: '[email protected]' });

if (result.success) {
  const user: User = result.data;
  console.log(user.id); // 42

  // Assertion form — narrows type, throws SpellValidationError on failure
  UserSchema.assert(result.data, 'user');
} else {
  const { fieldErrors, formErrors } = result.error.flattenFirst();
  console.log(fieldErrors, formErrors);
}

Documentation

• Overview
• Usage Guide
• API Reference
• Examples

License

MIT © Helmuth Saatkamp — part of the Vielzeug monorepo.