Source Generators
Five Roslyn incremental source generators handle all discovery and wiring at build time:
| Generator | Output | Purpose |
|---|---|---|
DependencyInjectionGenerator |
MediatorServiceRegistry.g.cs |
Scans for IRequestHandler, INotificationHandler, IStreamRequestHandler, and self-handling request classes. Emits adapter classes for self-handlers. Registers stateless handlers (no constructor params) as Singleton, others as Transient |
MediatorPipelineGenerator |
MediatorRegistry.g.cs |
Registers PipelineChainHandler<TRequest, TResponse> as transient for every request type via PrecompilePipelines(). Also populates RequestObjectDispatch with a delegate per request type for Send(object) runtime-typed dispatch |
MediatorExtensionsGenerator |
MediatorExtensions.g.cs |
Generates typed extension methods on ISender / IMediator (e.g. Send(Ping), CreateStream(PingStream)) so the compiler infers both generic type parameters. Uses defensive isinst + virtual-dispatch fallback (never branchless castclass) to ensure correct behavior in test projects, mocking scenarios, and dotnet test -c Release pipelines |
NotificationGenerator |
NotificationRegistry.g.cs |
Generates static dispatch arrays for each notification type, eliminating runtime service enumeration |
StreamGenerator |
StreamRegistry.g.cs |
Generates static factory delegates for each stream handler |
Compile-Time Diagnostics
The source generators also emit diagnostics to catch handler misconfigurations at build time:
| Rule | Severity | Description |
|---|---|---|
| DSOFT001 | Warning | No IRequestHandler<TRequest, TResponse> found for a request type |
| DSOFT002 | Warning | Multiple request handlers for the same <TRequest, TResponse> — only the last registered handler executes |
| DSOFT003 | Warning | Multiple stream handlers for the same <TRequest, TResponse> — only the last registered handler executes |
| DSOFT005 | Warning | A handler in a referenced assembly was discovered but skipped because it is internal and the consuming assembly does not have InternalsVisibleTo access. The message includes the handler type name and the source assembly |
Note: Multiple
INotificationHandler<T>implementations for the same notification type are expected and do not trigger a diagnostic — notification fan-out is by design.
Interceptor Generators
Three additional generators emit C# interceptors that replace ISender.Send, IPublisher.Publish, and IMediator.CreateStream call sites at compile time:
| Generator | Intercepts | Key optimization |
|---|---|---|
SendInterceptorGenerator |
ISender.Send<TRequest, TResponse>() |
Branchless castclass in Release (GDV-optimized) |
PublishInterceptorGenerator |
IPublisher.Publish<TNotification>() |
NotificationPublisherFlag bypass — skips DI probe |
StreamInterceptorGenerator |
IMediator.CreateStream<TRequest, TResponse>() |
Direct static dispatch |
All three interceptor generators adapt to OptimizationLevel: Release builds emit branchless castclass for JIT GDV; Debug builds emit isinst fallback for mock safety. Typed extensions (from MediatorExtensionsGenerator) always use defensive isinst + virtual-dispatch fallback regardless of build configuration — this ensures they work correctly in dotnet test -c Release CI pipelines where interceptors may be suppressed. See Performance Design for details.
Suppressing interceptors
Set <DSoftMediatorSuppressInterceptors>true</DSoftMediatorSuppressInterceptors> in your project to disable all interceptor generation — the project falls back to standard virtual dispatch through IMediator / ISender interfaces.
| Rule | Severity | Description |
|---|---|---|
| DSOFT004 | Warning | A mocking library (Moq, NSubstitute, FakeItEasy, JustMock, RhinoMocks, NimbleMocks) is referenced with interceptors enabled. In Release builds interceptors use a branchless cast that throws InvalidCastException on mock objects |