Using Valibot for Recursive Schema Validation

#typescript #demo #valibot

Recursive Type in TypeScript

TypeScript allows defining recursive types. For example, consider the following User interface:

interface User {
 children?: User;
 email: `${string}@${string}`;
 password: string;
}

Using Valibot for Schema Validation

What if you use a schema library, like Zod or Valibot? The schema has been built on value-level, and you cannot assign the variant to its property inside the declaration.

import * as v from 'valibot';

const EmailSchema = v.string([v.minLength(1), v.email()]);
const PasswordSchema = v.string([v.minLength(1), v.minLength(8)]);
// const UserSchema?

Recursive Schema

Base on the Author's reply in this issue, you can use v.lazy(() => UserSchema) and to create a type of the UserSchema as a type param to the v.BaseSchema genre as a type inference of the UserSchema:

type UserSchemaType = {
 children?: UserSchemaType;
 email: v.Input<typeof EmailSchema>;
 password: v.Input<typeof PasswordSchema>;
}

const UserSchema: v.BaseSchema<UserSchemaType> = v.object({
 children: v.optional(v.lazy(() => UserSchema)),
 email: EmailSchema,
 password: PasswordSchema,
});