How to create a Partial-like that requires a single property to be set

Question

We have a structure that is like the following:

export type LinkRestSource = {
    model: string;
    rel?: string;
    title?: string;
} | {
    model?: str         


        

Answer 1

A simpler version of the solution by jcalz:

type AtLeastOne = { [K in keyof T]: Pick }[keyof T]

so the whole implementation becomes

type FullLinkRestSource = {
  model: string;
  rel: string;
  title: string;
}

type AtLeastOne = { [K in keyof T]: Pick }[keyof T]
type LinkRestSource = AtLeastOne

const okay0: LinkRestSource = { model: 'a', rel: 'b', title: 'c' }
const okay1: LinkRestSource = { model: 'a', rel: 'b' }
const okay2: LinkRestSource = { model: 'a' }
const okay3: LinkRestSource = { rel: 'b' }
const okay4: LinkRestSource = { title: 'c' }

const error0: LinkRestSource = {} // missing property
const error1: LinkRestSource = { model: 'a', titel: 'c' } // excess property on string literal

and here's the TS playground link to try it