States

AsyncData<A> tracks three internal signals: optional value, optional error, and optional pending start time (via Luxon DateTime). The public state field derives from their combination.

State diagram (simplified)

Empty ──pending()──► Pending ──ready(v)──► Ready
  │                    │                      │
  │                    │ fail(e)              │ pending()
  │                    ▼                      ▼
  │                 Failed              PendingStale
  │                    │                      │
  │                    │                      │ ready(v) / fail(e)
  └────────────────────┴──────────────────────┘

Predicates

Property	True when
isEmpty	No value stored
nonEmpty	Value is present
isPending	A pending start time is set
isReady	Has value and is not stale
isStale	Has value and (pending or failed)
isFailed	An error is stored

isReady means “show the success path.” isStale means “we have a value but should indicate loading or error overlay.”

Duration

While pending, duration() returns elapsed milliseconds since pending() was called (Luxon UTC by default):

data.duration().map((ms) => `${ms}ms`);

Zipping

zip combines two AsyncData values into a tuple. Pending start times and errors merge according to the “latest start” and “first error wins” rules — useful when coordinating parallel requests.

Immutability

All transitions return new instances. Store the latest reference in React state or a reducer; do not mutate in place.