Getting Started

MonadicSharp.Recovery adds two recovery operators to MonadicSharp pipelines — RescueAsync for single-attempt recovery and StartFixBranchAsync for multi-attempt recovery.

Install

dotnet add package MonadicSharp.Recovery

Requires: .NET 8.0+, MonadicSharp ≥ 1.5.

RescueAsync — single recovery

using MonadicSharp.Recovery;

var result = await FetchUserAsync(userId)
    .RescueAsync(
        when: err => err is UserError.NotFound,
        recover: _ => CreateGuestUserAsync());

// If FetchUserAsync fails with UserError.NotFound → CreateGuestUserAsync() is tried.
// If CreateGuestUserAsync also fails → the new error propagates.
// All other errors from FetchUserAsync pass through unchanged.

StartFixBranchAsync — multi-attempt recovery

var result = await CallExternalApiAsync(request)
    .StartFixBranchAsync(
        when: err => err is ApiError.RateLimit or ApiError.Timeout,
        maxAttempts: 3,
        delay: TimeSpan.FromSeconds(2),
        fix: _ => CallExternalApiAsync(request));

// Attempts recovery up to 3 times with 2-second delays.
// On exhaustion, returns the last error from the fix attempts.

With telemetry

var telemetry = new MyRecoveryTelemetry(logger);

var result = await FetchDataAsync()
    .RescueAsync(
        when: err => err is DataError.Stale,
        recover: _ => RefreshAndFetchAsync(),
        telemetry: telemetry);  // optional

Three-lane model

Input → [ Green track: success path ] → Output ✅
            ↓ on matching error
         [ Amber track: recovery ]
            ↓ on recovery success    ↓ on recovery failure
         [ Back to Green ✅ ]      [ Red track ❌ ]

Next steps

• The Three Lanes — conceptual overview
• RescueAsync API — full parameter reference
• StartFixBranchAsync API — multi-attempt recovery reference