memoizeFuture<T> function

Future<T> Function() memoizeFuture<T>(AsyncAction<T> fn)

Cache single async result (memoize Future). Returns a function that runs fn once and reuses the same Future. Roadmap #180.

CAVEAT: the result is cached unconditionally, INCLUDING a failure. If fn's future rejects, every later call returns that same rejected future — the operation is never retried. Use a retrying helper (e.g. the idempotent-run utility, which evicts on completion) when failures should be retried. Audited: 2026-06-12 11:26 EDT

Implementation

Future<T> Function() memoizeFuture<T>(AsyncAction<T> fn) {
  Future<T>? cached;
  return () async {
    final future = cached ??= fn();
    return await future;
  };
}