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prefer-unwrapping-future-or

added in: 1.4.0
warning
Pro+

Warns when a FutureOr is not unwrapped before being used.

Awaiting FutureOr without checking if the returned value is actually a Future results in unnecessary async gap.

Example​

❌ Bad:

FutureOr<int> futureOrFunction() async => 1;

Future<void> main() async {
  await futureOrFunction(); // LINT: Ensure that the type of this expression is 'Future' before awaiting it.
}

✅ Good:

FutureOr<int> futureOrFunction() async => 1;

Future<void> main() async {
  final futureOr = futureOrFunction();

  int result;
  if (futureOr is Future) {
    result = await futureOr;
  } else {
    result = futureOr;
  }

  // Or

  final value = futureOr is Future ? await futureOr : futureOr;
}

Additional Resources​