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REslava.Result — Visual Result pipelines for .NET

.NET C# NuGet Version License GitHub contributors GitHub Stars NuGet Downloads Test Coverage Test Suite

Visual Result pipelines for .NET

Don't try to understand the pipeline—watch the flow.

Build Railway-Oriented pipelines with strongly typed errors, automatically generated flow diagrams, and built-in runtime observation — trace every node, debug visually.
✏️ Write Add [ResultFlow] — Mermaid diagram constants generated at compile time
▶️ Run Make your class partial — FlowProxy traces every node (output, type, elapsed ms)
🐛 Debug Drop a reslava-*.json — VS Code Debug Panel replays the trace on your live diagram

nuget-package-reslava-result GitHub repo

Auto-generated pipeline diagram — full type travel, typed error edges, async markers

[ResultFlow] — one attribute, live Mermaid diagram of your pipeline. Type travel, async markers, named error edges — generated from your code.

VS Code sidebar, diagram panel and Debug Panel walkthrough

🎯 Typed Error Pipelines — compile-time failure edges with Result<TValue, TError> (v1.39.0)

Replace IEnumerable<IError> bags with exact, exhaustive error types. Each Bind step grows the error union by one slot (ErrorsOf<T1,T2,...>). At the callsite, Match is exhaustive — the compiler tells you if you missed a case.

→ Typed Error Pipelines

🗺️ See how your Result<T> / Result<T, TError> flows — before it runs. Pipeline Visualization.

Annotate any fluent pipeline with [ResultFlow] and with single-click code action ResultFlow will insert a Mermaid diagram comment — every success path, failure branch, and side effect visualized. For Result<T, TError> pipelines, failure edges show the exact error type (ErrorsOf<ValidationError, InventoryError>) — no body scanning, reads directly from the return type.

→ ResultFlow

⚡ Quick start — Pipeline Visualization

Choose your track based on which Result library you use:

Track A Track B
Use when Using REslava.Result Any other Result library — ErrorOr, LanguageExt, FluentResults, or custom
Install REslava.Result + REslava.Result.Flow REslava.ResultFlow
Analysis Full semantic — typed error edges, type travel, FAIL annotation, body scanning Syntax-only — library-agnostic, convention file
Diagram constants _Diagram · _TypeFlow · _LayerView · _Stats · _ErrorSurface · _ErrorPropagation _Diagram · _TypeFlow

Track A: dotnet add package REslava.Result + dotnet add package REslava.Result.Flow

Track B: dotnet add package REslava.ResultFlow

VS Code extension (both tracks): REslava.Result Extensions — Flow Catalog sidebar + ▶ Open diagram preview CodeLens.

📚 New to functional programming? Start with the progressive tutorial series.

9 self-contained lessons that teach functional & railway-oriented programming step by step — from plain C# exceptions all the way to async pipelines and ASP.NET. Each lesson is a standalone dotnet run, no setup required.

Learn all three packages progressively: REslava.Result · REslava.ResultFlow · REslava.Result.AspNetCore

YouTube video series — coming soon.

→ Tutorial Lessons

  • Getting Started
    Installation, quick start, and the transformation (70-90% less code).

  • Core Concepts
    Functional programming foundation: Result, composition, async, Maybe, OneOf, validation, and more.

  • ASP.NET Integration Minimal API, MVC, SmartEndpoints, OpenAPI, authorization, and problem details.

  • Typed Error Pipelines ErrorsOf<T1..T8> + Result<TValue, TError> — compile-time typed failure edges, exhaustive match.

  • Safety Analyzers 7 Roslyn diagnostics + 3 code fixes — catch Result<T> and OneOf mistakes at compile time.

  • Architecture & Design How the library is built – SOLID, package structure, and the source generator pipeline.

  • Tutorial Series 9 progressive lessons — functional & railway-oriented programming from scratch. REslava.Result · REslava.ResultFlow · REslava.Result.AspNetCore. YouTube series coming soon.

  • Code examples Code examples: Fast APIs, Console and quick code examples.

  • Testing & Quality 3,339+ tests, CI/CD, real‑world impact, and production benefits.

  • Demo Project Runnable console app — every [ResultFlow] and [DomainBoundary] feature with live generated diagrams.

  • Live Panel & Diagnostics REslava.Result.Diagnostics — HTTP trace endpoint + VSIX Live panel with History / Single / Step / Replay modes. ▶ Debug CodeLens streams per-node execution data into VS Code.

  • Reference Version history, roadmap, and API documentation.

  • Community
    Contributing, license, and acknowledgments.

Why REslava.Result?

A Result pattern library for .NET with typed errors, Railway-Oriented pipelines, and automatic flow diagrams generated from your code.

What REslava.Result gives you:

Pillar Features
Railway-oriented pipelines Result<T>, Bind, Map, Ensure, Tap, Or, MapError — sync + async
Typed error pipelines Result<T,TError>, ErrorsOf<T1..T8> — compile-time error type safety
Rich domain errors ValidationError, ForbiddenError, NotFoundError, ConflictError, ExceptionError + TagKey<T>, DomainTags, SystemTags
Error metadata & context ReasonMetadata (caller info), ResultContext (entity / correlation / tenant / operation), auto-enrichment
Pipeline visualization [ResultFlow] → auto-generated Mermaid diagrams from your code
Framework integrations ASP.NET Core Smart Endpoints, FluentValidation, OpenTelemetry, HTTP client mapping
Safety analyzers RESL10xx / RESL20xx Roslyn analyzers enforcing correct usage patterns

⚡ Performance benchmarks — Ok creation 9.6× faster than FluentResults · failure handling 6.8× faster than exceptions · measured on .NET 9 with BenchmarkDotNet.

Feature Comparison

REslava.Result FluentResults ErrorOr LanguageExt
Result<T> pattern ✅ ✅ ✅ ✅
✨ Pipeline visualization ([ResultFlow]) ✅ — — —
OneOf discriminated unions ✅ (2-8 types) — — ✅
Typed error pipelines (ErrorsOf + Result<T,TError>) ✅ — — —
Maybe<T> ✅ — — ✅
ASP.NET source generators (Minimal API + MVC) ✅ — — —
SmartEndpoints (zero-boilerplate APIs) ✅ — — —
OpenAPI metadata auto-generation ✅ — — —
Authorization & Policy support ✅ — — —
Roslyn safety analyzers ✅ — — —
JSON serialization (System.Text.Json) ✅ — — —
Async patterns (WhenAll, Retry, Timeout) ✅ — — —
Domain error hierarchy (NotFound, Validation, etc.) ✅ — Partial —
Validation framework ✅ Basic — ✅
FluentValidation bridge (optional, migration only) ✅ — — —
Zero dependencies (core) ✅ ✅ ✅ —
Ok creation speed 5.9 ns / 48 B 57 ns / 112 B — —
Failure path vs exceptions 6.8× faster ~5.8× faster — —

Ready to Transform Your Error Handling?

📖 Start with the Getting Started Guide

⭐ Star this REslava.Result repository if you find it useful!

Made with ❤️ by Rafa Eslava for the developer community

Report Bug • Request Feature • Discussions