@decs/typeschema

🛵 TypeSchema

Unified interface for TypeScript schema validations

Many libraries rely on some sort of type validation. Their maintainers have the choice of either to:

1. ⁠Implement their own validation logic: which leads to more code to maintain, and we already have many good solutions out there (e.g. zod, arktype, typia)
2. Couple their code with a specific validation library: which limits adoption by developers who use another
3. Support multiple validation libraries: which is a burden to keep up-to-date (tRPC picked this one)

There's no best validation library because there's always a tradeoff. Each developer chooses the library that makes the most sense to them. TypeSchema solves this problem by providing option 3 (support multiple validation libraries) out-of-the-box.

Features

• 🚀 Decouple your code from validation libraries
• 🍃 Less than 3 kB, zero dependencies
• ✨ Easy-to-use, minimal API

Setup

Install TypeSchema with your package manager of choice:

npm	npm install @decs/typeschema
Yarn	yarn add @decs/typeschema
pnpm	pnpm add @decs/typeschema

Usage

import type {Infer, Schema} from '@decs/typeschema';
import {assert} from '@decs/typeschema';

// Use your favorite validation library, e.g. `zod`
const schema: Schema<string> = z.string();

// Extracts the schema type
type Type = Infer<typeof schema>; // `string`

// Returns the validated value or throws an exception
await assert(schema, '123'); // '123'
await assert(schema, 123); // `ZodError`

API

Types

• Schema<T>
  Generic schema
• Infer<T as Schema<unknown>>
  Extracts the equivalent TypeScript type of a schema

Functions

• assert<T>(schema: Schema<T>, data: unknown): Promise<T>
  Returns the validated value or throws an exception

Coverage

Project	Popularity	Example schema	Support
zod		z.string()	✅
yup		string()	✅
joi		Joi.string()	✅
superstruct		string()	✅
io-ts		t.string	❌
ow		ow.string	❌
typebox		Type.String()	❌
typia		typia.createAssert<string>()	✅
runtypes		String	✅
arktype		type('string')	✅

Custom validations are also supported:

export function assertString(value: unknown): string {
  if (typeof value !== 'string') {
    throw new Error('Expected a string, got: ' + value);
  }
  return value;
}

await assert(assertString, '123'); // Returns '123'
await assert(assertString, 123); // Throws an exception

Acknowledgement

• Inspired by tRPC's input & output validators