Don't throw error if no handlers were found for plain event message t…

…ypes

Changelog.md

@@ -1,5 +1,8 @@
 # Changelog
 
+## v.0.24.3
+- Don't throw error by default if no handlers were found for plain event message types
+
 ## v.0.24.2
 - Allow aborting the execution of handlers by calling `Abort` on the execution context.
 

src/Directory.Build.props

@@ -5,7 +5,7 @@
  <LangVersion>latest</LangVersion>
  <Authors>A. Shafie</Authors>
  <PackageTags>mediator;cqrs</PackageTags>
- <VersionPrefix>0.24.2</VersionPrefix>
+ <VersionPrefix>0.24.3</VersionPrefix>
  <PackageIcon>icon.png</PackageIcon>
  <Description>LiteBus is an easy-to-use and ambitious in-process mediator providing the foundation to implement Command Query Separation (CQS). It is implemented with minimal reflection and instead utilizes covariance and contravariance to provide its core functionality.</Description>
  <PackageProjectUrl>https://github.com/litenova/LiteBus</PackageProjectUrl>

src/LiteBus.Events/EventMediator.cs

@@ -30,7 +30,8 @@ public Task PublishAsync(IEvent @event, EventMediationSettings? eventMediationSe
  MessageMediationStrategy = mediationStrategy,
  MessageResolveStrategy = resolveStrategy,
  CancellationToken = cancellationToken,
- Tags = eventMediationSettings.Filters.Tags
+ Tags = eventMediationSettings.Filters.Tags,
+ RegisterPlainMessagesOnSpot = !eventMediationSettings.ThrowIfNoHandlerFound
  });
  }
 
@@ -46,7 +47,8 @@ public Task PublishAsync(IEvent @event, EventMediationSettings? eventMediationSe
  MessageMediationStrategy = mediationStrategy,
  MessageResolveStrategy = resolveStrategy,
  CancellationToken = cancellationToken,
- Tags = eventMediationSettings.Filters.Tags
+ Tags = eventMediationSettings.Filters.Tags,
+ RegisterPlainMessagesOnSpot = !eventMediationSettings.ThrowIfNoHandlerFound
  });
  }
 }

src/LiteBus.Messaging.Abstractions/Exceptions/MessageNotRegisteredException.cs

@@ -3,10 +3,9 @@
 namespace LiteBus.Messaging.Abstractions;
 
 [Serializable]
-internal class MessageNotRegisteredException : Exception
+public class NoHandlerFoundException : Exception
 {
- public MessageNotRegisteredException(Type messageType) :
- base($"The message type '{messageType.Name}' is not registered")
+ public NoHandlerFoundException(Type messageType) : base($"No handler found for message type '{messageType.Name}'")
  {
  }
 }

src/LiteBus.Messaging.Abstractions/FindStrategies/ActualTypeOrFirstAssignableTypeMessageResolveStrategy.cs

@@ -1,11 +1,12 @@
-using System;
+#nullable enable
+using System;
 using System.Linq;
 
 namespace LiteBus.Messaging.Abstractions;
 
 public sealed class ActualTypeOrFirstAssignableTypeMessageResolveStrategy : IMessageResolveStrategy
 {
- public IMessageDescriptor Find(Type messageType, IMessageRegistry messageRegistry)
+ public IMessageDescriptor? Find(Type messageType, IMessageRegistry messageRegistry)
  {
  if (messageType.IsGenericType)
  {
@@ -15,11 +16,6 @@ public IMessageDescriptor Find(Type messageType, IMessageRegistry messageRegistr
  var descriptor = messageRegistry.SingleOrDefault(d => d.MessageType == messageType) ??
  messageRegistry.FirstOrDefault(d => d.MessageType.IsAssignableFrom(messageType));
 
- if (descriptor is null)
- {
- throw new MessageNotRegisteredException(messageType);
- }
-
  return descriptor;
  }
 }

src/LiteBus.Messaging.Abstractions/IMessageResolveStrategy.cs

@@ -1,8 +1,9 @@
-using System;
+#nullable enable
+using System;
 
 namespace LiteBus.Messaging.Abstractions;
 
 public interface IMessageResolveStrategy
 {
- IMessageDescriptor Find(Type messageType, IMessageRegistry messageRegistry);
+ IMessageDescriptor? Find(Type messageType, IMessageRegistry messageRegistry);
 }

src/LiteBus.Messaging.Abstractions/MediateOptions.cs

@@ -13,4 +13,12 @@ public sealed class MediateOptions<TMessage, TMessageResult>
 
  // TODO: temporary placement for tags. Need to find a better place
  public required IEnumerable<string> Tags { get; init; }
+
+ /// <summary>
+ /// Indicates whether to register plain messages on spot. Plain messages are messages that do not implement any interfaces.
+ /// </summary>
+ /// <remarks>
+ /// 
+ /// </remarks>
+ public bool RegisterPlainMessagesOnSpot { get; init; } = false;
 }

src/LiteBus.Messaging/Internal/Mediator/MessageMediator.cs

@@ -33,6 +33,19 @@ internal sealed class MessageMediator : IMessageMediator
  // Find the message descriptor
  var descriptor = options.MessageResolveStrategy.Find(messageType, _messageRegistry);
 
+ if (descriptor is null)
+ {
+ if (!options.RegisterPlainMessagesOnSpot)
+ {
+ throw new NoHandlerFoundException(messageType);
+ }
+ else
+ {
+ _messageRegistry.Register(messageType);
+ descriptor = options.MessageResolveStrategy.Find(messageType, _messageRegistry);
+ }
+ }
+
  // resolve the dependencies in lazy mode
  var messageDependencies = new MessageDependencies(messageType, descriptor, _serviceProvider, options.Tags);
 

tests/LiteBus.Events.UnitTests/EventModuleTests.cs

@@ -2,11 +2,13 @@
 using LiteBus.Events.Abstractions;
 using LiteBus.Events.Extensions.MicrosoftDependencyInjection;
 using LiteBus.Events.UnitTests.UseCases;
+using LiteBus.Events.UnitTests.UseCases.EventWithNoHandlers;
 using LiteBus.Events.UnitTests.UseCases.EventWithTag;
 using LiteBus.Events.UnitTests.UseCases.ProblematicEvent;
 using LiteBus.Events.UnitTests.UseCases.ProductCreated;
 using LiteBus.Events.UnitTests.UseCases.ProductUpdated;
 using LiteBus.Events.UnitTests.UseCases.ProductViewed;
+using LiteBus.Messaging.Abstractions;
 using LiteBus.Messaging.Extensions.MicrosoftDependencyInjection;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -279,4 +281,50 @@ public async Task mediating_the_an_event_with_both_all_available_tags_goes_throu
  @event.ExecutedTypes[8].Should().Be<EventWithTagEventHandlerPostHandler2>();
  @event.ExecutedTypes[9].Should().Be<GlobalEventPostHandler>();
  }
+
+ [Fact]
+ public async Task mediating_the_an_event_with_no_handlers_should_not_throw_exception_when_ThrowIfNoHandlerFound_is_set_false()
+ {
+ var serviceProvider = new ServiceCollection()
+ .AddLiteBus(configuration => { configuration.AddEventModule(builder => { builder.RegisterFromAssembly(typeof(ProblematicEventPreHandler).Assembly); }); })
+ .BuildServiceProvider();
+
+ var eventMediator = serviceProvider.GetRequiredService<IEventMediator>();
+
+ var @event = new EventWithNoHandlers();
+
+ var settings = new EventMediationSettings
+ {
+ ThrowIfNoHandlerFound = false,
+ };
+
+ // Act
+ await eventMediator.PublishAsync(@event, settings);
+
+ // Assert
+ @event.ExecutedTypes.Should().HaveCount(0);
+ }
+
+ [Fact]
+ public async Task mediating_the_an_event_with_no_handlers_should_throw_exception_when_ThrowIfNoHandlerFound_is_set_true()
+ {
+ var serviceProvider = new ServiceCollection()
+ .AddLiteBus(configuration => { configuration.AddEventModule(builder => { builder.RegisterFromAssembly(typeof(ProblematicEventPreHandler).Assembly); }); })
+ .BuildServiceProvider();
+
+ var eventMediator = serviceProvider.GetRequiredService<IEventMediator>();
+
+ var @event = new EventWithNoHandlers();
+
+ var settings = new EventMediationSettings
+ {
+ ThrowIfNoHandlerFound = true,
+ };
+
+ // Act
+ var act = () => eventMediator.PublishAsync(@event, settings);
+
+ // Assert
+ await act.Should().ThrowAsync<NoHandlerFoundException>();
+ }
 }

tests/LiteBus.Events.UnitTests/UseCases/EventWithNoHandlers/EventWithNoHandlers.cs

@@ -0,0 +1,6 @@
+namespace LiteBus.Events.UnitTests.UseCases.EventWithNoHandlers;
+
+public class EventWithNoHandlers
+{
+ public List<Type> ExecutedTypes { get; } = new();
+}