Source Generator

TurboMediator uses a Roslyn Incremental Source Generator to produce compile-time optimized code. This is the core of the library's performance advantage.

What Gets Generated

The source generator produces:

1. Mediator class — The concrete IMediator implementation with switch-expression dispatch for each message type
2. ExecuteWithPipeline method — Resolves pre-processors, pipeline behaviors, exception handlers, and post-processors from DI and chains them
3. AddTurboMediator() extension — DI registration that wires all discovered handlers

Example Generated Code

For a project with PingRequest and GetUserQuery:

// Generated by TurboMediator Source Generator
internal sealed class Mediator : IMediator
{
    private readonly IServiceProvider _serviceProvider;

    public Mediator(IServiceProvider serviceProvider)
    {
        _serviceProvider = serviceProvider;
    }

    public ValueTask<TResponse> Send<TResponse>(IRequest<TResponse> request, CancellationToken ct)
    {
        return request switch
        {
            PingRequest msg => ExecuteWithPipeline<PingRequest, string>(msg, ct),
            _ => throw new InvalidOperationException($"No handler for {request.GetType().Name}")
        };
    }

    public ValueTask<TResponse> Send<TResponse>(IQuery<TResponse> query, CancellationToken ct)
    {
        return query switch
        {
            GetUserQuery msg => ExecuteWithPipeline<GetUserQuery, User?>(msg, ct),
            _ => throw new InvalidOperationException($"No handler for {query.GetType().Name}")
        };
    }

    // ... similar for Commands and Notifications
}

No Reflection

The key benefit is that dispatch is a compile-time switch expression — no Dictionary<Type, Handler> lookups, no Activator.CreateInstance, no MethodInfo.Invoke. This makes it:

• Faster than reflection-based mediators
• Compatible with Native AOT publishing
• Fully trimmable by the .NET linker

Build-Time Diagnostics

The source generator emits diagnostics during compilation:

Example Build Errors

error TURBO002: Multiple handlers found for 'GetUserQuery': GetUserHandler, AnotherGetUserHandler
error TURBO008: Handler 'InternalHandler' must be public to be discovered by TurboMediator
warning TURBO001: No handler found for message 'OrphanedCommand'

How It Works Internally

1. Parser Phase: Scans the syntax tree for:

   • Classes implementing handler interfaces (IRequestHandler, ICommandHandler, IQueryHandler, INotificationHandler, streaming variants)
   • Types implementing message interfaces (IRequest, ICommand, IQuery, INotification, streaming variants)

2. Validation Phase: Checks for:

   • Missing handlers
   • Duplicate handlers
   • Signature mismatches
   • Accessibility (public)

3. Emission Phase: Generates:

   • Mediator class with switch-expression routing
   • Pipeline execution with DI-resolved behaviors
   • AddTurboMediator() service collection extension