AvoidUnawaitedFutureRule class

Warns when a Future is not awaited and not explicitly marked.

Since: v2.3.10 | Updated: v4.13.0 | Rule version: v3

Implementation note for developers: Expression statements whose expression is a call to unawaited(...) are never reported. The check uses node.expression (the statement's expression), not node.parent, so that unawaited(someFuture()); is correctly recognized as intentional fire-and-forget regardless of static type resolution. When we don't report: (1) the expression is unawaited(...), (2) safe fire-and-forget patterns (subscription.cancel() in dispose, .catchError()/.ignore(), etc.).

Quick fix available: Wrap in unawaited().

Alias: unawaited_future, missing_await, fire_and_forget

Unawaited Futures lose their errors and can cause unexpected behavior. Either await the Future or use unawaited() to explicitly mark it.

BAD:

void doSomething() {
  saveData(); // Future returned but not awaited
}

GOOD:

Future<void> doSomething() async {
  await saveData();
}

// Or if intentionally fire-and-forget:
void doSomething() {
  unawaited(saveData());
}

ALLOWED (safe fire-and-forget patterns):

// StreamSubscription.cancel() in dispose() - can't await in sync method
@override
void dispose() {
  _subscription?.cancel(); // OK - disposal cleanup
  super.dispose();
}

// Future chains with .catchError() - errors are handled
_scrollController.animateTo(100).catchError((e) {
  debugPrint('Animation failed: $e');
}); // OK - error is handled

// Future.ignore() - explicitly ignored
someAsyncOperation().ignore(); // OK - explicitly fire-and-forget