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🛵 TypeSchema

Universal adapter for schema validation

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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
  • ✨ 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, 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 a `ValidationIssue`
await assert(schema, '123'); // '123'
await assert(schema, 123); // throws `ValidationIssue`

// 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 `ValidationIssue`

Coverage

TypeSchema supports all major schema validation libraries:

Project Popularity Example schema Support
zod GitHub stars z.string() ✅
yup GitHub stars string() ✅
joi GitHub stars Joi.string() ✅[^1]
ajv GitHub stars {type: "string"} ✅[^1]
superstruct GitHub stars string() ✅[^2]
io-ts GitHub stars t.string ✅
ow GitHub stars ow.string ✅[^3]
typia GitHub stars typia.createAssert<string>() ✅
typebox GitHub stars Type.String() ✅
deepkit GitHub stars typeOf<string>() ✅[^1]
runtypes GitHub stars String ✅
arktype GitHub stars type('string') ✅
valibot GitHub stars string() ✅

[^1]: Type inference is not yet supported for joi, ajv, and deepkit [^2]: Input type inference is not yet supported for superstruct [^3]: 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 `ValidationIssue`

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

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 a ValidationIssue

  • 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