typebox/docs/types/unsafe.md

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Unsafe Types

TypeBox supports user defined types with Unsafe. This type allows you to specify both schema representation and inference type. The following creates an Unsafe type with a number schema that infers as string.

const T = Type.Unsafe<string>({ type: "number" }); // const T = { type: 'number' }

type T = Static<typeof T>; // type T = string - ?

The Unsafe type is often used to create schematics for extended specifications like OpenAPI.

const Nullable = <T extends TSchema>(schema: T) =>
  Type.Unsafe<Static<T> | null>({
    ...schema,
    nullable: true,
  });

const T = Nullable(Type.String()); // const T = {
//   type: 'string',
//   nullable: true
// }

type T = Static<typeof T>; // type T = string | null

const StringEnum = <T extends string[]>(values: [...T]) =>
  Type.Unsafe<T[number]>({
    type: "string",
    enum: values,
  });
const S = StringEnum(["A", "B", "C"]); // const S = {
//   enum: ['A', 'B', 'C']
// }

type S = Static<typeof T>; // type S = 'A' | 'B' | 'C'

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