🛵 TypeSchema

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 (e.g. tRPC)

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 easily providing option 3: support multiple validation libraries out-of-the-box.

Features

• 🚀 Decouple from validation libraries
• 🍃 Tiny client footprint, tree-shakeable
• ✨ Easy-to-use, minimal API

Usage

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

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

// Extracts the schema type
type Output = Infer<typeof schema>; // `string`
type Input = InferIn<typeof schema>; // `string`

// Returns the validated data or throws an `AggregateError`
await assert(schema, '123'); // '123'
await assert(schema, 123); // throws `AggregateError`

// Returns the validated data or a list of `ValidationIssue`s
await validate(schema, '123'); // {data: '123'}
await validate(schema, 123); // {issues: [`ValidationIssue`]}

// Returns an assertion function for a specific schema
const assertString = createAssert(schema);
await assertString('123'); // '123'
await assertString(123); // throws `AggregateError`

Coverage

TypeSchema supports all major schema validation libraries:

Project	Popularity	validate assert	Infer	InferIn	Example schema
zod		✅	✅	✅	z.string()
yup		✅	✅	✅	string()
joi		✅	❌	❌	Joi.string()
ajv		✅	❌	❌	{type: "string"}
superstruct		✅	✅	❌	string()
io-ts		✅	✅	✅	t.string
ow[^1]		✅	✅	✅	ow.string
typia		✅	✅	✅	typia.createAssert<string>()
typebox		✅	✅	✅	Type.String()
valibot		✅	✅	✅	string()
deepkit		✅	❌	❌	typeOf<string>()
runtypes		✅	✅	✅	String
arktype		✅	✅	✅	type('string')

[^1]: For ow, only v0.28.2 is supported (sindresorhus/ow#248)

Custom validations are also supported:

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

await assert(assertString, '123'); // '123'
await assert(assertString, 123); // throws `AggregateError`

await validate(assertString, '123'); // {data: '123'}
await validate(assertString, 123); // {issues: [`ValidationIssue`]}

Setup

Install TypeSchema with your package manager of choice:

Vite

If using Vite, you’ll also need to update your vite.config.ts file:

import {typeschemaPlugin} from '@decs/typeschema/vite';

export default defineConfig({
  plugins: [
    typeschemaPlugin(), // add this plugin
  ],
});

API

Types

• Schema

  Generic interface for schemas
  An union of the schema types of all supported libraries

• ValidationIssue

  Generic interface for validation issues
  Includes a message: string and an optional path?: Array<string | number | symbol>

• Infer<TSchema extends Schema>

  Extracts the output type of a schema

• InferIn<TSchema extends Schema>

  Extracts the input type of a schema

Functions

• assert(schema, data)

  assert<TSchema extends Schema>(
    schema: TSchema,
    data: unknown,
  ): Promise<Infer<TSchema>>

  Returns the validated data or throws an AggregateError

• validate(schema, data)

  validate<TSchema extends Schema>(
    schema: TSchema,
    data: unknown,
  ): Promise<{data: Infer<TSchema>} | {issues: Array<ValidationIssue>}>

  Returns the validated data or a list of ValidationIssues

• createAssert(schema)

  createAssert<TSchema extends Schema>(
    schema: TSchema,
  ): (data: unknown) => Promise<Infer<TSchema>>

  Returns an assertion function for a specific schema

Acknowledgements

• Inspired by tRPC’s input & output validators
• Adapter architecture inspired by @ecyrbe’s suggestions
• API definition inspired by @colinhacks’s proposal