Discriminated Union

[lifeiscontent]

I created this Type, to be specifically used for OpenAPI:

import {
  TSchema,
  Kind,
  Static,
  SchemaOptions,
  CreateType,
  Never,
  TObject,
  TRef,
} from "@sinclair/typebox";

type DiscriminatedUnionStatic<
  T extends TObject[] | TRef<TObject>[],
  P extends unknown[]
> = {
  [K in keyof T]: T[K] extends TSchema ? Static<T[K], P> : never;
}[number];

export interface DiscriminatedUnion<
  T extends TObject[] | TRef<TObject>[] = TObject[] | TRef<TObject>[]
> extends TSchema {
  [Kind]: "DiscriminatedUnion";
  static: DiscriminatedUnionStatic<T, this["params"]>;
  oneOf: T;
  type: "object";
  discriminator: {
    propertyName: keyof T[number];
  };
}

function DiscriminatedUnionCreate<T extends TObject[] | TRef<TObject>[]>(
  propertyName: keyof T[number],
  T: [...T],
  options?: SchemaOptions
): DiscriminatedUnion<T> {
  return CreateType(
    {
      [Kind]: "DiscriminatedUnion",
      oneOf: T,
      type: "object",
      discriminator: {
        propertyName,
      },
    },
    options
  ) as never;
}

export function DiscriminatedUnion<T extends TObject[] | TRef<TObject>[]>(
  propertyName: keyof T[number],
  T: [...T],
  options?: SchemaOptions
): DiscriminatedUnion<T> {
  return (
    T.length === 0
      ? Never(options)
      : T.length === 1
      ? CreateType(T[0], options)
      : DiscriminatedUnionCreate(propertyName, T, options)
  ) as DiscriminatedUnion<T>;
}

I just wanted to get your take on using it, I'm currently using Fastify with Ajv but was wondering if I need to register this with the TypeRegistry of Typebox or not.

You can see the usage here: https://github.com/lifeiscontent/fastify-example/pull/1

[lifeiscontent]

@sinclairzx81 ^

[ehaynes99]

Your example link is broken. Is it private?