BbQ.Outcome 1.0.2

Outcome

Outcome is a modern C# functional result type inspired by ErrorOr.
It builds on the excellent foundation of ErrorOr by adding async workflows, LINQ query syntax, deconstruction, Source Link, and multi-targeting — making error-aware programming feel like a first-class citizen in modern .NET.

✨ Why Outcome?

ErrorOr pioneered the idea of replacing exceptions with a discriminated union of either a value or errors.
Outcome takes this idea further:

• Structured errors: Rich Error record with Code, Description, and Severity.
• Async composition: BindAsync, MapAsync, CombineAsync for natural async pipelines.
• LINQ integration: Native Select/SelectMany support for sync + async queries.
• Deconstruction: Tuple-style unpacking (isSuccess, value, errors) for ergonomic handling.
• Friendly ToString: Human-readable logging like Success: 42 or Errors: [DIV_ZERO: Division by zero].
• Multi-targeting: Works across netstandard2.0, net6.0, and net8.0.
• Source Link enabled: Step directly into source when debugging NuGet packages.
• Source generator support: Auto-generate Error<T> helper properties from enums with the [QbqOutcome] attribute.

🚀 Example

var query =
    from x in ParseAsync("10")
    from y in DivideAsync(x, 2)
    select y * 2;

var (ok, value, errors) = await query;

Console.WriteLine(ok
    ? $"Result: {value}"
    : $"Errors: {string.Join("; ", errors.Select(e => e.Description))}");

Output:

Result: 10

📦 Installation

dotnet add package BbQ.Outcome

🔧 Source Generator: Error Helper Properties

The [QbqOutcome] attribute enables automatic generation of Error<TCode> helper properties for enums. This eliminates boilerplate and keeps error definitions DRY.

Usage

Mark your error enum with [QbqOutcome]:

[QbqOutcome]
public enum ApiErrorCode
{
    /// <summary>
    /// The requested resource was not found.
    /// </summary>
    NotFound,

    /// <summary>
    /// The user does not have permission to access this resource.
    /// </summary>
    Unauthorized,

    /// <summary>
    /// An internal server error occurred.
    /// </summary>
    InternalError
}

The source generator automatically creates a static class ApiErrorCodeErrors with helper properties:

// Generated code (do not edit)
public static class ApiErrorCodeErrors
{
    public static Error<ApiErrorCode> NotFoundError =>
        new(
            ApiErrorCode.NotFound,
            "The requested resource was not found.",
            ErrorSeverity.Error
        );

    public static Error<ApiErrorCode> UnauthorizedError =>
        new(
            ApiErrorCode.Unauthorized,
            "The user does not have permission to access this resource.",
            ErrorSeverity.Error
        );

    public static Error<ApiErrorCode> InternalErrorError =>
        new(
            ApiErrorCode.InternalError,
            "An internal server error occurred.",
            ErrorSeverity.Error
        );
}

Benefits

• Zero boilerplate: No manual Error<TCode> construction.
• Documentation-driven: Descriptions are extracted from XML doc comments (<summary> tags).
• Consistent naming: Property names follow the pattern {EnumMember}Error.
• Type-safe: Full compile-time type checking with Error<YourEnumType>.

How It Works

1. The generator scans for enums decorated with [QbqOutcome].
2. For each enum member, it extracts the summary from XML documentation comments.
3. It generates a static helper class with pre-constructed Error<T> properties.
4. If no documentation is found, it falls back to the enum member name.