From 8b1ee39fe29fd12c8042d22f9fd1a969b5fcbc16 Mon Sep 17 00:00:00 2001
From: Jimmy Bogard <jimmy.bogard@gmail.com>
Date: Thu, 16 Nov 2023 16:08:24 +0100
Subject: [PATCH] Adding configuration to auto-register request processors

---
 .../MediatrServiceConfiguration.cs            |  5 ++++
 src/MediatR/Registration/ServiceRegistrar.cs  | 14 ++++++++++-
 .../MicrosoftExtensionsDI/PipelineTests.cs    | 23 +++++++++++++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/MediatR/MicrosoftExtensionsDI/MediatrServiceConfiguration.cs b/src/MediatR/MicrosoftExtensionsDI/MediatrServiceConfiguration.cs
index 539d0b2c..53712c42 100644
--- a/src/MediatR/MicrosoftExtensionsDI/MediatrServiceConfiguration.cs
+++ b/src/MediatR/MicrosoftExtensionsDI/MediatrServiceConfiguration.cs
@@ -64,6 +64,11 @@ public class MediatRServiceConfiguration
     /// </summary>
     public List<ServiceDescriptor> RequestPostProcessorsToRegister { get; } = new();
 
+    /// <summary>
+    /// Automatically register processors during assembly scanning
+    /// </summary>
+    public bool AutoRegisterRequestProcessors { get; set; }
+
     /// <summary>
     /// Register various handlers from assembly containing given type
     /// </summary>
diff --git a/src/MediatR/Registration/ServiceRegistrar.cs b/src/MediatR/Registration/ServiceRegistrar.cs
index 721312eb..28ba295d 100644
--- a/src/MediatR/Registration/ServiceRegistrar.cs
+++ b/src/MediatR/Registration/ServiceRegistrar.cs
@@ -21,13 +21,25 @@ public static void AddMediatRClasses(IServiceCollection services, MediatRService
         ConnectImplementationsToTypesClosing(typeof(IRequestExceptionHandler<,,>), services, assembliesToScan, true, configuration);
         ConnectImplementationsToTypesClosing(typeof(IRequestExceptionAction<,>), services, assembliesToScan, true, configuration);
 
-        var multiOpenInterfaces = new[]
+        if (configuration.AutoRegisterRequestProcessors)
+        {
+            ConnectImplementationsToTypesClosing(typeof(IRequestPreProcessor<>), services, assembliesToScan, false, configuration);
+            ConnectImplementationsToTypesClosing(typeof(IRequestPostProcessor<,>), services, assembliesToScan, false, configuration);
+        }
+
+        var multiOpenInterfaces = new List<Type>
         {
             typeof(INotificationHandler<>),
             typeof(IRequestExceptionHandler<,,>),
             typeof(IRequestExceptionAction<,>)
         };
 
+        if (configuration.AutoRegisterRequestProcessors)
+        {
+            multiOpenInterfaces.Add(typeof(IRequestPreProcessor<>));
+            multiOpenInterfaces.Add(typeof(IRequestPostProcessor<,>));
+        }
+
         foreach (var multiOpenInterface in multiOpenInterfaces)
         {
             var arity = multiOpenInterface.GetGenericArguments().Length;
diff --git a/test/MediatR.Tests/MicrosoftExtensionsDI/PipelineTests.cs b/test/MediatR.Tests/MicrosoftExtensionsDI/PipelineTests.cs
index 3722a378..6d5276a1 100644
--- a/test/MediatR.Tests/MicrosoftExtensionsDI/PipelineTests.cs
+++ b/test/MediatR.Tests/MicrosoftExtensionsDI/PipelineTests.cs
@@ -846,6 +846,29 @@ public void Should_handle_open_behaviors_registration_from_a_single_type()
         });
     }
 
+    [Fact]
+    public void Should_auto_register_processors_when_configured()
+    {
+        var cfg = new MediatRServiceConfiguration
+        {
+            AutoRegisterRequestProcessors = true
+        };
+
+        var output = new Logger();
+        IServiceCollection services = new ServiceCollection();
+        services.AddSingleton(output);
+
+        cfg.RegisterServicesFromAssemblyContaining<Ping>();
+
+        services.AddMediatR(cfg);
+
+        var provider = services.BuildServiceProvider();
+
+        provider.GetServices(typeof(IRequestPreProcessor<Ping>)).Count().ShouldBeGreaterThan(0);
+        provider.GetServices(typeof(IRequestPostProcessor<Ping, Pong>)).Count().ShouldBeGreaterThan(0);
+    }
+
+
     public sealed record FooRequest : IRequest;
     
     public interface IBlogger<T>