Make auto registration of generic handlers opt in.

Author: zachpainter77

src/MediatR/MicrosoftExtensionsDI/MediatrServiceConfiguration.cs

@@ -92,7 +92,7 @@ public class MediatRServiceConfiguration
     /// <summary>
     /// Flag that controlls whether MediatR will attempt to register handlers that containg generic type parameters.
     /// </summary>
-    public bool RegisterGenericHandlers { get; set; } = true;
+    public bool RegisterGenericHandlers { get; set; } = false;
 
     /// <summary>
     /// Register various handlers from assembly containing given type

test/MediatR.Tests/GenericRequestHandlerTests.cs

@@ -32,6 +32,7 @@ public void ShouldResolveAllCombinationsOfGenericHandler(int numberOfClasses, in
             services.AddMediatR(cfg =>
             {
                 cfg.RegisterServicesFromAssemblies(dynamicAssembly);
+                cfg.RegisterGenericHandlers = true;
             });
 
             var provider = services.BuildServiceProvider();
@@ -106,6 +107,7 @@ public void ShouldThrowExceptionWhenTypesClosingExceedsMaximum()
                 services.AddMediatR(cfg =>
                 {
                     cfg.RegisterServicesFromAssembly(assembly);
+                    cfg.RegisterGenericHandlers = true;
                 });
             })
             .Message.ShouldContain("One of the generic type parameter's count of types that can close exceeds the maximum length allowed");
@@ -124,6 +126,7 @@ public void ShouldThrowExceptionWhenGenericHandlerRegistrationsExceedsMaximum()
                 services.AddMediatR(cfg =>
                 {
                     cfg.RegisterServicesFromAssembly(assembly);
+                    cfg.RegisterGenericHandlers = true;
                 });
             })
             .Message.ShouldContain("The total number of generic type registrations exceeds the maximum allowed");
@@ -142,6 +145,7 @@ public void ShouldThrowExceptionWhenGenericTypeParametersExceedsMaximum()
                 services.AddMediatR(cfg =>
                 {
                     cfg.RegisterServicesFromAssembly(assembly);
+                    cfg.RegisterGenericHandlers = true;
                 });
             })
             .Message.ShouldContain("The number of generic type parameters exceeds the maximum allowed");
@@ -163,6 +167,7 @@ public void ShouldThrowExceptionWhenTimeoutOccurs()
                     cfg.MaxGenericTypeRegistrations = 0;
                     cfg.MaxTypesClosing = 0;
                     cfg.RegistrationTimeout = 1000;
+                    cfg.RegisterGenericHandlers = true;
                     cfg.RegisterServicesFromAssembly(assembly);
                 });
             })

test/MediatR.Tests/MicrosoftExtensionsDI/AssemblyResolutionTests.cs

@@ -15,7 +15,11 @@ public AssemblyResolutionTests()
     {
         IServiceCollection services = new ServiceCollection();
         services.AddSingleton(new Logger());
-        services.AddMediatR(cfg => cfg.RegisterServicesFromAssembly(typeof(Ping).Assembly));
+        services.AddMediatR(cfg =>
+        {
+            cfg.RegisterServicesFromAssembly(typeof(Ping).Assembly);
+            cfg.RegisterGenericHandlers = true;
+        });
         _provider = services.BuildServiceProvider();
     }
 

test/MediatR.Tests/SendTests.cs

@@ -18,7 +18,11 @@ public SendTests()
     {
         _dependency = new Dependency();
         var services = new ServiceCollection();
-        services.AddMediatR(cfg => cfg.RegisterServicesFromAssemblies(typeof(Ping).Assembly));
+        services.AddMediatR(cfg =>
+        {
+            cfg.RegisterServicesFromAssemblies(typeof(Ping).Assembly);
+            cfg.RegisterGenericHandlers = true;
+        });
         services.AddSingleton(_dependency);
         _serviceProvider = services.BuildServiceProvider();
         _mediator = _serviceProvider.GetService<IMediator>()!;
@@ -248,8 +252,13 @@ public async Task Should_resolve_closed_handler_if_defined()
     {
         var dependency = new Dependency();
         var services = new ServiceCollection();
-        services.AddSingleton(dependency);       
-        services.AddMediatR(cfg => cfg.RegisterServicesFromAssemblies(Assembly.GetExecutingAssembly()));
+        services.AddSingleton(dependency);
+        services.AddMediatR(cfg =>
+        {
+            cfg.RegisterServicesFromAssemblies(Assembly.GetExecutingAssembly());
+            cfg.RegisterGenericHandlers = true;
+        });
+
         services.AddTransient<IRequestHandler<VoidGenericPing<PongExtension>>,TestClass1PingRequestHandler>();
         var serviceProvider = services.BuildServiceProvider();
         var mediator = serviceProvider.GetService<IMediator>()!;
@@ -267,7 +276,11 @@ public async Task Should_resolve_open_handler_if_not_defined()
         var dependency = new Dependency();
         var services = new ServiceCollection();
         services.AddSingleton(dependency);
-        services.AddMediatR(cfg => cfg.RegisterServicesFromAssemblies(Assembly.GetExecutingAssembly()));
+        services.AddMediatR(cfg => 
+        {
+            cfg.RegisterServicesFromAssemblies(Assembly.GetExecutingAssembly());
+            cfg.RegisterGenericHandlers = true;
+        });
         services.AddTransient<IRequestHandler<VoidGenericPing<PongExtension>>, TestClass1PingRequestHandler>();
         var serviceProvider = services.BuildServiceProvider();
         var mediator = serviceProvider.GetService<IMediator>()!;