Function memoizeAsync

pwa/utils/memoizeAsync.ts:13–31

(
  fn: (...args: Args) => Promise<R>,
  keyFn: (...args: Args) => string = (...args) => JSON.stringify(args)
)

 * rejection is evicted so failures are not memoized.
 */
export function memoizeAsync<Args extends any[], R>(
  fn: (...args: Args) => Promise<R>,
  keyFn: (...args: Args) => string = (...args) => JSON.stringify(args)
): (...args: Args) => Promise<R> {
  const store = new Map<string, Promise<R>>();

  return (...args: Args): Promise<R> => {
    const key = keyFn(...args);
    const existing = store.get(key);
    if (existing) return existing;

    const promise = fn(...args).catch((error) => {
      store.delete(key);
      throw error;
    });
    store.set(key, promise);
    return promise;
  };
}