Merge pull request #1057 from zachpainter77/master

Make Auto Registration of Generic Handlers OPT-IN

Author: jbogard

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

src/MediatR/Registration/ServiceRegistrar.cs

@@ -228,10 +228,7 @@ private static (Type Service, Type Implementation) GetConcreteRegistrationTypes(
         var constraintsForEachParameter = openRequestHandlerImplementation
             .GetGenericArguments()
             .Select(x => x.GetGenericParameterConstraints())
-            .ToList();
-
-        if (constraintsForEachParameter.Count > 2 && constraintsForEachParameter.Any(constraints => !constraints.Where(x => x.IsInterface || x.IsClass).Any()))
-            throw new ArgumentException($"Error registering the generic handler type: {openRequestHandlerImplementation.FullName}. When registering generic requests with more than two type parameters, each type parameter must have at least one constraint of type interface or class.");
+            .ToList();
 
         var typesThatCanCloseForEachParameter = constraintsForEachParameter
             .Select(constraints => assembliesToScan

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();
@@ -93,24 +94,6 @@ public void ShouldNotRegisterDuplicateHandlers(int numberOfClasses, int numberOf
             hasDuplicates.ShouldBeFalse();
         }
 
-        [Fact]
-        public void ShouldThrowExceptionWhenRegisterningHandlersWithNoConstraints()
-        {
-            IServiceCollection services = new ServiceCollection();
-            services.AddSingleton(new Logger());
-
-            var assembly = GenerateMissingConstraintsAssembly();
-
-            Should.Throw<ArgumentException>(() =>
-            {
-                services.AddMediatR(cfg =>
-                {
-                    cfg.RegisterServicesFromAssembly(assembly);
-                });
-            })
-            .Message.ShouldContain("When registering generic requests with more than two type parameters, each type parameter must have at least one constraint of type interface or class.");
-        }
-
         [Fact]
         public void ShouldThrowExceptionWhenTypesClosingExceedsMaximum()
         {
@@ -124,6 +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");
@@ -142,6 +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");
@@ -160,6 +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");
@@ -181,6 +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/MicrosoftExtensionsDI/BaseGenericRequestHandlerTests.cs

@@ -9,11 +9,7 @@
 namespace MediatR.Tests.MicrosoftExtensionsDI
 {
     public abstract class BaseGenericRequestHandlerTests
-    {      
-        
-        protected static Assembly GenerateMissingConstraintsAssembly() =>
-           CreateAssemblyModuleBuilder("MissingConstraintsAssembly", 3, 3, CreateHandlerForMissingConstraintsTest);
-
+    { 
         protected static Assembly GenerateTypesClosingExceedsMaximumAssembly() =>
             CreateAssemblyModuleBuilder("ExceedsMaximumTypesClosingAssembly", 201, 1, CreateHandlerForExceedsMaximumClassesTest);
 

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>()!;