Support for explicit assemblies configuration (where to find messages and handlers) (#202)

Author: martinothamar

README.md

@@ -271,6 +271,7 @@ services.AddMediator((MediatorOptions options) =>
     options.ServiceLifetime = ServiceLifetime.Singleton;
     // Only available from v3:
     options.NotificationPublisherType = typeof(Mediator.ForeachAwaitPublisher);
+    options.Assemblies = [typeof(...)];
     options.PipelineBehaviors = [];
     options.StreamPipelineBehaviors = [];
 });
@@ -286,9 +287,13 @@ services.AddMediator((MediatorOptions options) =>
   * `Transient` - mediator and handlers registered as transient
   * `Scoped`    - mediator and handlers registered as scoped
 * `NotificationPublisherType` - the type used for publishing notifications (`ForeachAwaitPublisher` and `TaskWhenAllPublisher` are built in)
+* `Assemblies` - which assemblies the source generator should scan for messages and handlers. When not used the source generator will scan all references assemblies (same behavior as v2)
 * `PipelineBehaviors`/`StreamPipelineBehaviors` - ordered array of types used for the pipeline
   * The source generator adds DI regristrations manually as oppposed to open generics registrations, to support NativeAOT. You can also manually add pipeline behaviors to the DI container if you are not doing AoT compilation.
 
+Note that since parsing of these options is done during compilation/source generation, all values must be compile time constants.
+In addition, since some types are not valid attributes parameter types (such as arrays/lists), some configuration is only available through `AddMediator`/`MediatorOptions` and not the assembly attribute.
+
 Singleton lifetime is highly recommended as it yields the best performance.
 Every application is different, but it is likely that a lot of your message handlers doesn't keep state and have no need for transient or scoped lifetime.
 In a lot of cases those lifetimes only allocate lots of memory for no particular reason.
@@ -334,6 +339,8 @@ using var serviceProvider = services.BuildServiceProvider();
 ### 4.3. Create `IRequest<>` type
 
 ```csharp
+services.AddMediator((MediatorOptions options) => options.Assemblies = [typeof(Ping)]);
+using var serviceProvider = services.BuildServiceProvider();
 var mediator = serviceProvider.GetRequiredService<IMediator>();
 var ping = new Ping(Guid.NewGuid());
 var pong = await mediator.Send(ping);
@@ -366,6 +373,7 @@ Pipeline behaviors currently must be added manually.
 ```csharp
 services.AddMediator((MediatorOptions options) =>
 {
+    options.Assemblies = [typeof(Ping)];
     options.PipelineBehaviors = [typeof(PingValidator)];
 });
 
@@ -391,6 +399,7 @@ Message pre- and post-processors along with the exception handlers can also cons
 ```csharp
 services.AddMediator((MediatorOptions options) =>
 {
+    options.Assemblies = [typeof(ErrorMessage)];
     options.PipelineBehaviors = [typeof(ErrorLoggerHandler<,>)];
 });
 

samples/Showcase/Program.cs

@@ -8,16 +8,19 @@
 
 var services = new ServiceCollection();
 
-services.AddMediator(options =>
-{
-    options.NotificationPublisherType = typeof(FireAndForgetNotificationPublisher);
-    options.PipelineBehaviors =
-    [
-        // Ordering of pipeline behavior registrations matter!
-        typeof(ErrorLoggerHandler<,>),
-        typeof(PingValidator),
-    ];
-});
+services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Assemblies = [typeof(Ping)];
+        options.NotificationPublisherType = typeof(FireAndForgetNotificationPublisher);
+        options.PipelineBehaviors =
+        [
+            // Ordering of pipeline behavior registrations matter!
+            typeof(ErrorLoggerHandler<,>),
+            typeof(PingValidator),
+        ];
+    }
+);
 
 var sp = services.BuildServiceProvider();
 

samples/apps/ASPNET_Core/Program.cs

@@ -1,3 +1,6 @@
+using ASPNETCore.WeatherForecasts;
+using Mediator;
+
 var builder = WebApplication.CreateBuilder(args);
 
 // Add services to the container.
@@ -8,7 +11,12 @@
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddSwaggerGen();
 
-builder.Services.AddMediator();
+builder.Services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Assemblies = [typeof(GetWeatherForecasts).Assembly];
+    }
+);
 
 var app = builder.Build();
 

samples/apps/ASPNET_Core_CleanArchitecture/AspNetCoreSample.Application/ServiceCollectionExtensions.cs

@@ -7,10 +7,13 @@ public static class ServiceCollectionExtensions
 {
     public static IServiceCollection AddApplication(this IServiceCollection services)
     {
-        services.AddMediator(options =>
-        {
-            options.ServiceLifetime = ServiceLifetime.Scoped;
-        });
+        services.AddMediator(
+            (MediatorOptions options) =>
+            {
+                options.Assemblies = [typeof(AddTodoItem)];
+                options.ServiceLifetime = ServiceLifetime.Scoped;
+            }
+        );
         return services
             .AddSingleton(typeof(IPipelineBehavior<,>), typeof(ErrorLoggingBehaviour<,>))
             .AddSingleton(typeof(IPipelineBehavior<,>), typeof(MessageValidatorBehaviour<,>));

samples/apps/ASPNET_Core_Indirect/AspNetCoreIndirect.Application/Program.cs

@@ -1,3 +1,6 @@
+using AspNetCoreIndirect.Application;
+using Mediator;
+
 var builder = WebApplication.CreateBuilder(args);
 
 // Add services to the container.
@@ -8,7 +11,12 @@
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddSwaggerGen();
 
-builder.Services.AddMediator();
+builder.Services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Assemblies = [typeof(GetWeatherForecast)];
+    }
+);
 
 var app = builder.Build();
 

samples/apps/InternalMessages/InternalMessages.Api/Program.cs

@@ -1,9 +1,16 @@
+using InternalMessages.Application;
 using InternalMessages.Domain;
+using Mediator;
 using Microsoft.AspNetCore.Mvc;
 
 var builder = WebApplication.CreateBuilder(args);
 
-builder.Services.AddMediator();
+builder.Services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Assemblies = [typeof(Ping), typeof(PingHandler)];
+    }
+);
 
 var app = builder.Build();
 

samples/basic/Console/Program.cs

@@ -8,10 +8,13 @@
 
 // This extensions method is generated, and is put in the "Microsoft.Extensions.DependencyInjection" namespace.
 // We override the namespace in the "MediatorOptions" object.
-services.AddMediator(options =>
-{
-    options.Namespace = "SimpleConsole";
-});
+services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Namespace = "SimpleConsole";
+        options.Assemblies = [typeof(Ping)];
+    }
+);
 
 // Standard handlers are added by default, but we need to add pipeline steps manually.
 // Here are two examples.

samples/basic/ConsoleAOT/Program.cs

@@ -5,17 +5,20 @@
 
 // This extensions method is generated, and is put in the "Mediator" namespace by default.
 // We override the namespace in the "MediatorOptions" object.
-services.AddMediator(options =>
-{
-    options.Namespace = "SimpleConsoleAOT";
-    options.PipelineBehaviors =
-    [
-        // Standard handlers are added by default, but we need to add pipeline steps manually.
-        // Here are two examples.
-        typeof(GenericLoggerHandler<,>), // This will run 1st
-        typeof(PingValidator), // This will run 2nd
-    ];
-});
+services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Namespace = "SimpleConsoleAOT";
+        options.Assemblies = [typeof(Ping)];
+        options.PipelineBehaviors =
+        [
+            // Standard handlers are added by default, but we need to add pipeline steps manually.
+            // Here are two examples.
+            typeof(GenericLoggerHandler<,>), // This will run 1st
+            typeof(PingValidator), // This will run 2nd
+        ];
+    }
+);
 
 var serviceProvider = services.BuildServiceProvider();
 

samples/basic/NetFramework/Console/Program.cs

@@ -14,10 +14,13 @@ static async Task<int> Main(string[] args)
 
             // This extensions method is generated, and is put in the "Microsoft.Extensions.DependencyInjection" namespace.
             // We override the namespace in the "MediatorOptions" object.
-            services.AddMediator(options =>
-            {
-                options.Namespace = "SimpleConsole";
-            });
+            services.AddMediator(
+                (MediatorOptions options) =>
+                {
+                    options.Namespace = "SimpleConsole";
+                    options.Assemblies = new AssemblyReference[] { typeof(Ping) };
+                }
+            );
 
             // Standard handlers are added by default, but we need to add pipeline steps manually.
             // Here are two examples.

samples/basic/NotificationPublisher/Program.cs

@@ -7,10 +7,13 @@
 
 var services = new ServiceCollection();
 
-services.AddMediator(options =>
-{
-    options.NotificationPublisherType = typeof(MyNotificationPublisher);
-});
+services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Assemblies = [typeof(Notification)];
+        options.NotificationPublisherType = typeof(MyNotificationPublisher);
+    }
+);
 
 var serviceProvider = services.BuildServiceProvider();
 

samples/basic/Notifications/Program.cs

@@ -6,7 +6,12 @@
 
 var services = new ServiceCollection();
 
-services.AddMediator();
+services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Assemblies = [typeof(Notification)];
+    }
+);
 
 var serviceProvider = services.BuildServiceProvider();
 

samples/basic/Streaming/Program.cs

@@ -9,7 +9,12 @@
 var services = new ServiceCollection();
 
 // This extensions method is generated, and is put in the "Mediator" namespace by default.
-services.AddMediator();
+services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Assemblies = [typeof(StreamPing)];
+    }
+);
 
 var serviceProvider = services.BuildServiceProvider();
 

samples/use-cases/Autofac_DI/Program.cs

@@ -6,11 +6,14 @@
 
 builder.Host.UseServiceProviderFactory(new AutofacServiceProviderFactory());
 
-builder.Services.AddMediator(config =>
-{
-    config.Namespace = "Foo.Generated";
-    config.ServiceLifetime = ServiceLifetime.Scoped;
-});
+builder.Services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Namespace = "Foo.Generated";
+        options.Assemblies = [typeof(Ping)];
+        options.ServiceLifetime = ServiceLifetime.Scoped;
+    }
+);
 
 var app = builder.Build();
 

samples/use-cases/MassTransitIntegration/Program.cs

@@ -6,7 +6,12 @@
 
 var builder = WebApplication.CreateBuilder(args);
 
-builder.Services.AddMediator((MediatorOptions options) => { });
+builder.Services.AddMediator(
+    (MediatorOptions options) =>
+    {
+        options.Assemblies = [typeof(WeatherUpdated)];
+    }
+);
 
 builder.Services.AddMassTransit(options =>
 {