CancelCop.Analyzer 1.4.8

CancelCop Analyzer

A surgical Roslyn analyzer focused on CancellationToken best practices: propagation, parameter positioning, loop cancellation checks, and more. Includes automatic code fixes.

Why CancelCop?

CancelCop helps you build responsive, cancellable .NET applications by ensuring CancellationToken is properly used throughout your codebase. It catches issues at compile time and provides automatic fixes.

Features

9 Comprehensive Analyzers

Automatic Code Fixes

• ✅ Adds CancellationToken parameters to method signatures
• ✅ Propagates tokens to inner async calls
• ✅ Adds cancellation checks to loops
• ✅ Handles lambda expressions (Minimal APIs)
• ✅ Smart using directive management
• ✅ Preserves code formatting

Quick Start

Installation

dotnet add package CancelCop.Analyzer

Usage

Once installed, the analyzer runs automatically during build. It will:

1. Detect CancellationToken issues in your code
2. Show warnings in your IDE with clear descriptions
3. Offer code fixes - just click the lightbulb 💡

Example

// ❌ Before (CC001 warning)
public async Task ProcessDataAsync()
{
    await Task.Delay(100);
}

// ✅ After (automatic fix applied)
public async Task ProcessDataAsync(CancellationToken cancellationToken = default)
{
    await Task.Delay(100, cancellationToken);
}

Supported Patterns

Entity Framework Core

await _context.Users.ToListAsync(cancellationToken);
await _context.Users.FirstOrDefaultAsync(u => u.Id == id, cancellationToken);
await _context.SaveChangesAsync(cancellationToken);

HttpClient

await httpClient.GetAsync(url, cancellationToken);
await httpClient.PostAsync(url, content, cancellationToken);
await httpClient.SendAsync(request, cancellationToken);

ASP.NET Core Controllers

[HttpGet]
public async Task<IActionResult> GetUsers(CancellationToken cancellationToken)
{
    var users = await _service.GetUsersAsync(cancellationToken);
    return Ok(users);
}

Minimal APIs

app.MapGet("/users", async (CancellationToken ct) =>
    await GetUsersAsync(ct));

MediatR Handlers

public class MyHandler : IRequestHandler<MyRequest, MyResponse>
{
    public async Task<MyResponse> Handle(
        MyRequest request,
        CancellationToken cancellationToken)
    {
        // ...
    }
}

Loop Cancellation (New in v1.3.0)

public async Task ProcessItemsAsync(List<Item> items, CancellationToken ct)
{
    foreach (var item in items)
    {
        ct.ThrowIfCancellationRequested();  // Analyzer ensures this is present
        await ProcessAsync(item, ct);
    }
}

Benefits

• 🎯 Responsive Applications: Properly cancel long-running operations
• 🚀 Better Performance: Avoid wasting resources on cancelled operations
• 🛡️ Production Ready: Reduce timeout issues and improve reliability
• ⚡ Developer Friendly: Automatic fixes save time and reduce errors
• 📊 Comprehensive: Covers all major .NET async patterns

Configuration

All rules are enabled by default with appropriate severity levels. Configure in .editorconfig:

[*.cs]
# Adjust severity (none, suggestion, warning, error)
dotnet_diagnostic.CC001.severity = warning
dotnet_diagnostic.CC006.severity = suggestion
dotnet_diagnostic.CC009.severity = warning

Supported Frameworks

• .NET 6.0+ (including .NET 8, .NET 9, .NET 10)
• ASP.NET Core (Controllers and Minimal APIs)
• Entity Framework Core (all async methods)
• HttpClient (all async methods)
• MediatR (IRequestHandler implementations)
• ValueTask and ValueTask<T> return types

Test Coverage

• 111 tests ensuring reliability
• All analyzers and code fixes thoroughly tested
• Covers edge cases and complex scenarios

Learn More

• GitHub Repository
• Report Issues
• Sample Project

Built with ❤️ using Roslyn and following TDD best practices.