optional_ctx_resolver.ts

gistfile1.txt

type GlobalCtx = {
  session: {
    authorize(): void;
  };
};

type LoginInputType = {
  email: string;
};

export type Fn = (...args: any) => Promise<any>;

export type ResolverDef<T extends Fn> = (
  input: Parameters<T>[0],
  ctx: GlobalCtx
) => ReturnType<T>;

export type CombinedResolver<T extends Fn> = (
  input: Parameters<T>[0],
  ctx?: GlobalCtx
) => ReturnType<T>;

function wrap<T extends ResolverDef<Fn>>(resolverDef: T): CombinedResolver<T>;
function wrap<T extends ResolverDef<Fn>>(resolverDef: T) {
  return (input: Parameters<T>[0], ctx: GlobalCtx) => {
    return resolverDef(input, ctx);
  };
}

const login = wrap(async function login(input: LoginInputType, ctx) {
  ctx.session.authorize();
  return true;
});

// I want both of these to be valid
login({ email: '' }, { session: { authorize: () => {} } });
login({ email: '' });