steady 1.2.0

A Result type library for Dart inspired by Rust's Result<T, E>. Provides type-safe error handling with rich utility methods.

steady

steady provides Result<T, E> and Option<T> for explicit, type-safe control flow in Dart. It is inspired by Rust and is intended for codebases that prefer modeling success, failure, and optional values without relying on unchecked exceptions or nullable values.

Features

• Explicit success and failure handling with Result<T, E extends Exception>
• Explicit optional values with Option<T>
• Sync and async transformation helpers
• Chaining and fallback APIs for readable workflows
• Immutable sealed data types with pattern matching support

Installation

Add the package to your pubspec.yaml:

dependencies:
  steady: ^1.1.1

Then install dependencies:

dart pub get

Quick Start

Import the package:

import 'package:steady/steady.dart';

Result

Create success and failure values:

final ok = Result<int, Exception>.ok(42);
final err = Result<int, Exception>.error(Exception('failed'));

Read values safely:

final value = ok.unwrap(); // 42
final fallback = err.unwrapOr(0); // 0

final computed = err.unwrapOrElse((error) {
  print('error: $error');
  return 0;
});

Transform and chain:

final result = Result<int, Exception>.ok(21)
    .map((value) => value * 2)
    .andThen((value) => Result.ok(value + 1));

print(result.unwrap()); // 43

Recover from errors:

final recovered = Result<int, Exception>.error(Exception('network'))
    .recover((error) => Result.ok(0));

print(recovered.unwrap()); // 0

Work with async callbacks:

final asyncResult = await Result<String, Exception>.ok('steady')
    .mapAsync((value) async => value.toUpperCase());

print(asyncResult.unwrap()); // STEADY

Option

Create present and absent values:

final some = Option.some(42);
final none = Option<int>.none();

Read values safely:

final value = some.unwrap(); // 42
final fallback = none.unwrapOr(0); // 0

Transform and chain:

final option = Option.some(21)
    .map((value) => value * 2)
    .andThen((value) => Option.some(value + 1));

print(option.unwrap()); // 43

Convert an Option to a Result:

final userId = Option<String>.none();

final result = userId.toResult(() => StateError('missing user id'));
print(result.isErr); // true

Core APIs

Result<T, E>:

• unwrap, unwrapOr, unwrapOrElse, expect
• map, mapAsync, mapErr, mapErrAsync
• andThen, andThenAsync
• orElse, orElseAsync, recover, recoverAsync
• fold

Option<T>:

• fromNullable
• unwrap, unwrapOr, unwrapOrElse, expect
• map, mapAsync
• andThen, andThenAsync
• orElse, orElseAsync
• filter, fold, toResult

Example

Future<Result<User, Exception>> fetchUser(ApiClient client, int id) async {
  try {
    final response = await client.getUser(id);
    return Result.ok(response);
  } on Exception catch (error) {
    return Result.error(error);
  }
}

Future<String> loadUserName(ApiClient client, int id) async {
  final result = await fetchUser(client, id);
  return result.map((user) => user.name).unwrapOr('Unknown');
}

Additional Resources

• API reference: https://pub.dev/documentation/steady/latest/
• Example app: example/example.dart
• Issue tracker: https://github.com/cos-overclock/steady/issues

Release Automation

This repository includes a GitHub Actions workflow at .github/workflows/release_publish.yml. When you push a tag like v1.1.1, GitHub Actions will:

• verify that the tag matches the version in pubspec.yaml
• create a GitHub Release using the matching section from CHANGELOG.md
• publish the package to pub.dev

The workflow runs on tag pushes regardless of which branch the tag was created from.

Before using it, configure automated publishing on pub.dev:

1. Open https://pub.dev/packages/steady/admin.
2. Enable publishing from GitHub Actions for cos-overclock/steady.
3. Set the tag pattern to v{{version}}.

This workflow uses GitHub OIDC via the official dart-lang/setup-dart reusable workflow, so no pub.dev API token needs to be stored as a GitHub secret.

If you enable a required GitHub Actions environment on pub.dev, add the same environment name to the publish job in .github/workflows/release_publish.yml.

License

This package is available under the MIT License. See LICENSE.