retry<T> method

Future<T> retry<T>(FutureOr<T> fn(), { FutureOr<bool> retryIf(Exception)?, FutureOr<void> onRetry(Exception)?, })

Call fn retrying so long as retryIf return true for the exception thrown.

At every retry the onRetry function will be called (if given). The function fn will be invoked at-most this.attempts times.

If no retryIf function is given this will retry any for any Exception thrown. To retry on an Error, the error must be caught and rethrown as an Exception.

Implementation

Future<T> retry<T>(
  FutureOr<T> Function() fn, {
  FutureOr<bool> Function(Exception)? retryIf,
  FutureOr<void> Function(Exception)? onRetry,
}) async {
  var attempt = 0;
  // ignore: literal_only_boolean_expressions
  while (true) {
    attempt++; // first invocation is the first attempt
    try {
      return await fn();
    } on Exception catch (e) {
      if (attempt >= maxAttempts ||
          (retryIf != null && !(await retryIf(e)))) {
        rethrow;
      }
      if (onRetry != null) {
        await onRetry(e);
      }
    }

    // Sleep for a delay
    await Future.delayed(delay(attempt));
  }
}