Pipeline diagrams generated at compile time are great for understanding structure. But structure tells you what could happen — not what did happen. That's where runtime observation comes in.

REslava.Result has a three-layer story:

✏️ Write — add [ResultFlow] to any fluent Result method. The source generator emits a Mermaid diagram constant at compile time. You can paste it into GitHub, Notion, VS Code, or mermaid.live and see the entire pipeline shape before you ever run it.

▶️ Run — make your class partial. The same generator now emits a FlowProxy alongside the diagram. Call svc.Flow.Process(...) instead of svc.Process(...) and every node in the pipeline is traced automatically: output value, error type, elapsed milliseconds. The RingBufferObserver holds the last N traces in memory with zero allocation.

🐛 Debug — call svc.Flow.Debug.Process(...) for a single-trace debug run. The generator writes reslava-debug-{Method}.json to your bin/ folder automatically. The VS Code extension watches */reslava-.json — the Debug Panel opens by itself, no manual trigger, no port to configure, no HTTP server.

Inside the Debug Panel:

• The pipeline diagram is rendered live


• Each trace is listed: pass/fail icon, method name, node count, elapsed ms total


• Step through nodes one at a time — the current step is highlighted in the diagram


• Animated replay — plays through all nodes automatically


• Multi-file picker — switch between trace files without closing the panel

The FlowProxy is generated — you write no observer wiring, no DI registration, no startup hooks. Make the class partial, rebuild, and you have full observability.

// You write

public partial class OrderService

{

[ResultFlow]

public Result Process(int userId, int productId) =>

FindUser(userId)

.Ensure(IsActive, new ForbiddenError("inactive"))

.Bind(u => FindProduct(productId))

.Ensure(InStock, new NotFoundError("out of stock"))

.Bind(PlaceOrder);

}

// You call (for debug):

svc.Flow.Debug.Process(userId, productId);

// → reslava-debug-Process.json written automatically

// → VSIX file watcher fires

// → Debug Panel opens with the trace, ready to step through

Everything generated. Nothing hand-written.

https://reslava.github.io/nuget-package-reslava-result/resultflow/runtime/

dotnet #csharp #sourcegenerators #debugging #railwayorientedprogramming #functionalprogramming #roslyn #developerexperience