Errors as values in dart

try_or_null.dart

import 'dart:io';

Future<void> main(List<String> arguments) async {
  final x1 = tryOrNull(() => throwing());
  print(x1);

  final (v1, e1) = tryTuple(() => throwing());
  print("$v1, $e1");

  final (v2, e2) = tryTuple(() => nonThrowing());
  print("$v2, $e2");

  final x2 = await tryOrNullAsync(() => timeout(), Duration(seconds: 1));
  print(x2);

  final (v3, e3) = await tryTupleAsync(() => timeout(), Duration(seconds: 1));
  print("$v3, $e3");

  final (v4, e4) = await tryTupleAsync(() => throwingAsync());
  print("$v4, $e4");

  final (v5, e5) = await tryTupleAsync(() => nonThrowingAsync());
  print("$v5, $e5");

  exit(0);
}

String throwing() {
  throw Exception('error message');
}

String nonThrowing() {
  return "foo";
}

Future<String> timeout() async {
  await Future.delayed(Duration(minutes: 30));
  return "foo";
}

Future<String> throwingAsync() async {
  await Future.delayed(Duration(milliseconds: 500));
  throw Exception('error message');
}

Future<String> nonThrowingAsync() async {
  await Future.delayed(Duration(milliseconds: 500));
  return "foo";
}

T? tryOrNull<T>(T Function() fn) {
  try {
    return fn();
  } catch (_) {
    return null;
  }
}

Future<T?> tryOrNullAsync<T>(Future<T> Function() fn,
    [Duration timeout = const Duration(minutes: 1)]) async {
  try {
    final x = await fn().timeout(timeout);
    return x;
  } catch (_) {
    return null;
  }
}

(T?, Object?) tryTuple<T>(T Function() fn) {
  try {
    return (fn(), null);
  } catch (e) {
    return (null, e);
  }
}

Future<(T?, Object?)> tryTupleAsync<T>(Future<T> Function() fn,
    [Duration timeout = const Duration(minutes: 1)]) async {
  try {
    final x = await fn().timeout(timeout);
    return (x, null);
  } catch (e) {
    return (null, e);
  }
}