Is there a way to add extra options after a type has been created

[bhuynhdev]

I wish to add extra options parameters to a type after it has been created, such as examples or format.

import { Type as t } from '@sinclair/typebox'

const S = t.String()

const S1 = t.MagicalExtend(S, { examples: ['home address']})

const S2 = t.MagicalExtend(S, {examples: ['date string']})

Is there a way to achieve this MagicalExtend (or perhaps MagicalRecreate) feature?

[sinclairzx81]

@bhuynhdev Hi,

TypeBox types just Json Schema objects, so you can just apply additional properties using the JavaScript spread operator. Below applies additional properties from T1 to T2, where we use typeof T1 to give a correct TSchema type of T2 (as they should be the same type)

import { Type as t } from '@sinclair/typebox'

const T1 = t.String()                       // const T1: TString = { type: 'string' }

const T2: typeof T1 = { foo: 'bar', ...T1 } // const T2: TString = { type: 'string', foo: 'bar' }

So, the above applies to all TB types. You may wish to implement a function to make application of additional properties more consistent (where the options are applied before the schema to ensure no properties are overwritten).

import { Type as t, TSchema } from '@sinclair/typebox'

export function MagicExtend<T extends TSchema>(schema: T, options: Record<PropertyKey, unknown>): T {
  return { ...options, ...schema }
}

const T1 = t.String()                       // const T1: TString = { type: 'string' }

const T2 = MagicExtend(T1, { foo: 'bar' })  // const T2: TString = { type: 'string', foo: 'bar' }

Hope this helps
S

[bhuynhdev]

@sinclairzx81 Hi. Thanks a lot for the lightning fast response. This is awesome. As a follow up on your solution, is there a way to get Typescript to infer the keys in the options parameter? For example, if T is Type.Number then options will autocomplete suggest maximum, minimum, whereas if T is Type.String then options will suggest format or minLength

Edit: Digging through the codebase, I found multiple kinds of options, so I wrote this. Unsure if this is correct.

type DynamicTypeboxSchemaOptions<T extends TSchema> = T extends TString
	? StringOptions
	: T extends TArray
	? ArrayOptions
	: T extends TNumber | TInteger
	? NumericOptions<number>
	: T extends TIntersect
	? IntersectOptions
	: T extends TObject | TPartial<T>
	? ObjectOptions
	: SchemaOptions

export function extendSchema<T extends TSchema>(schema: T, options: DynamicTypeboxSchemaOptions<T>): T {
	return { ...options, ...schema }
}

TComposite and TRecord did not have any special handling, as I deemed it to be a bit difficult, and my use case would never result in TComposite being passed to extendSchema anyway. (Use case: I am using Drizzle ORM's drizzle-typebox to createSelectSchema from Drizzle's table definition, but I sometimes need to extend the schema field to add examples and format and minLength)

[sinclairzx81]

@bhuynhdev No problem. You can try the following which should generalize across all types.

TypeScript Link Here

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

type DynamicTypeboxSchemaOptions<T extends TSchema, O extends Record<PropertyKey, unknown>> = T & O

export function extendSchema<T extends TSchema, O extends Record<PropertyKey, unknown> = {}>(schema: T, options: O): DynamicTypeboxSchemaOptions<T, O> {
	return { ...options, ...schema }
}

const T = Type.Object({
    x: Type.Number(),
    y: Type.String(),
    z: Type.Boolean()
})

const E = extendSchema(T, { foo: { bar: { baz: 1 } } } as const)

const N = E.foo.bar.baz   // const N: 1

type E = Static<typeof E> // ok