Schema of JSON Schema

[MatanYadaev]

Is there a way to make a schema of JSON schema with TypeBox?

AFAIK, this is a schema of JSON Schema 2019-09: https://json-schema.org/draft/2019-09/schema

Use case: I have an endpoint that clients can pass JSON Schemas, as part of the endpoint, I would like to check that this given schema is a valid JSON Schema.

[sinclairzx81]

@MatanYadaev Hi,

Is there a way to make a schema of JSON schema with TypeBox?

Yes, partially. However you may run into some challenges adequately expressing both the Json Schema specification while retaining type inference (as schematics can get recursive). This said, The following sets up a few Json Schema types and shows the Recursive / Generic pattern self referential schematics.

import { Type, TSchema, Static } from '@sinclair/typebox'
import { Value } from '@sinclair/typebox/value'

export const AnyOf = <T extends TSchema>(This: T) => Type.Object({
  anyOf: Type.Array(This)
})
export const AllOf = <T extends TSchema>(This: T) => Type.Object({
  allOf: Type.Array(This)
})
export const Object = <T extends TSchema>(This: T) => Type.Object({
  type: Type.Literal('object'),
  properties: Type.Record(Type.String(), This),
  required: Type.Array(Type.String())
})
export const Array = <T extends TSchema>(This: T) => Type.Object({
  type: Type.Literal('array'),
  items: This
})
export const String = Type.Object({ type: Type.Literal('string') })
export const Number = Type.Object({ type: Type.Literal('number') })
export const Boolean = Type.Object({ type: Type.Literal('boolean') })
export const Null = Type.Object({ type: Type.Literal('null') })

export type Schema = Static<typeof Schema>
export const Schema = Type.Recursive(This => Type.Union([
  AllOf(This),
  AnyOf(This),
  Object(This),
  Array(This),
  String,
  Number,
  Boolean,
  Null
]), { $id: 'Schema' })

// some tests
console.log(Schema)
console.log(Value.Check(Schema, { type: 'null' }))
console.log(Value.Check(Schema, { type: 'string' }))
console.log(Value.Check(Schema, { type: 'object', properties: {
  x: { type: 'number' }
}, required: ['x'] }))

Hope this helps S

[MatanYadaev]

Thanks @sinclairzx81 for the quick reply.

[nounderline]

Thank you @sinclairzx81

Creating JSON Schema of JSON Schema in TypeBox feels quite meta and powerful :)