foo.ts

export const delayUntil = <T>(
  signal$: RxJS.Observable<unknown>,
): RxJS.OperatorFunction<T, T> => ob$ =>
  ob$.pipe(
    RxJSOperators.publishReplay(undefined, undefined, publishedOb$ =>
      RxJS.concat(
        signal$.pipe(RxJSOperators.first(), RxJSOperators.mergeMapTo(RxJS.EMPTY)),
        publishedOb$,
      ),
    ),
  );

/**
 * Waits for a minimum time `ms` before emitting `ob$`.
 */
export const waitMinimumOf = <T>(ms: number): RxJS.OperatorFunction<T, T> => ob$ =>
  ob$.pipe(delayUntil(RxJS.timer(ms)));