TypeScript helpers

infer-example.ts

import { copyStream } from '../common/messages'

type Unarray<T> = T extends Array<infer R> ? R : T;
type Unobservable<T> = T extends Observable<infer R> ? R : T;
type Unpacked<T> = T extends Array<infer R> ? R : T extends Observable<infer R> ? R : never;

type CopyData = Unobservable<typeof copyStream>
type BackgroundEvent =
  | { type: 'copy'; data: CopyData }
  | { type: 'xstate.done.performCopy'; data: { tabId: string } }

negate.ts

export function not<Predicate extends (...args: any[]) => boolean>(
  fn: Predicate
): Predicate {
  // @ts-expect-error We're forwarding the args and negating the result
  return (...args: Parameters<Predicate>) => !fn(...args)
}