Arkn.Results 0.3.2

Arkn.Results

Conventions you can read. Patterns you can enforce.

Result<T> and Error — business failures as first-class types. No exceptions for domain logic.

Install

dotnet add package Arkn.Results

Quick example

// Return results, never throw
public Result<User> GetUser(Guid id)
{
    var user = _repo.Find(id);
    return user is null
        ? Error.NotFound("User.NotFound", $"User {id} not found.")
        : Result.Success(user);
}

// Consume with Match
return result.Match(
    onSuccess: user  => Ok(user),
    onFailure: error => error.Type switch
    {
        ErrorType.NotFound   => NotFound(),
        ErrorType.Validation => BadRequest(error.Message),
        _                    => Problem(error.Message)
    });

API

// Factories
Result.Success()                    // void success
Result.Success(value)               // typed success
Result<T>.Ok(value)                 // shorthand
Result.Failure(error)               // void failure
Result<T>.Fail(error)               // typed failure
Result<T>.Fail(errors)              // multiple errors

// Error factories — message is optional (defaults to code)
Error.NotFound("User.NotFound")                          // concise
Error.NotFound("User.NotFound", $"User '{id}' not found.") // explicit
Error.Validation("Order.QuantityInvalid")
Error.Conflict("Email.AlreadyRegistered")
Error.Unauthorized("Auth.TokenExpired")

// Chaining
result.Map(v => transform(v))
      .Bind(v => nextOperation(v))
      .Tap(v => sideEffect(v))
      .Match(onSuccess, onFailure);

ErrorGroup pattern

Group all errors for a domain in one static class:

public static class UserErrors
{
    public static Error NotFound(Guid id) =>
        Error.NotFound("User.NotFound", $"User '{id}' not found.");

    public static readonly Error InvalidEmail =
        Error.Validation("User.InvalidEmail", "Email is invalid.");

    public static readonly Error EmailAlreadyRegistered =
        Error.Conflict("User.EmailAlreadyRegistered", "Already in use.");
}

// Usage
return user is null ? UserErrors.NotFound(id) : Result.Success(user);

Part of the Arkn ecosystem

github.com/fernando-terra/arkn · nuget.org/packages/Arkn.Results