Merge pull request #1193 from json-api-dotnet/duplicate-controllers-error

Improve error message when duplicate controllers found

Author: maurei

Diff for: src/JsonApiDotNetCore/Middleware/JsonApiRoutingConvention.cs

@@ -78,7 +78,8 @@ public void Apply(ApplicationModel application)
                     {
                         if (_controllerPerResourceTypeMap.ContainsKey(resourceType))
                         {
-                            throw new InvalidConfigurationException($"Multiple controllers found for resource type '{resourceType}'.");
+                            throw new InvalidConfigurationException(
+                                $"Multiple controllers found for resource type '{resourceType}': '{_controllerPerResourceTypeMap[resourceType].ControllerType}' and '{controller.ControllerType}'.");
                         }
 
                         _resourceTypePerControllerTypeMap.Add(controller.ControllerType, resourceType);

Diff for: test/JsonApiDotNetCoreTests/IntegrationTests/NonJsonApiControllers/DuplicateResourceControllerTests.cs

@@ -20,6 +20,9 @@ public void Fails_at_startup_when_multiple_controllers_exist_for_same_resource_t
         Action action = () => _ = Factory;
 
         // Assert
-        action.Should().ThrowExactly<InvalidConfigurationException>().WithMessage("Multiple controllers found for resource type 'knownResources'.");
+        InvalidConfigurationException exception = action.Should().ThrowExactly<InvalidConfigurationException>().Which!;
+        exception.Message.Should().StartWith("Multiple controllers found for resource type 'knownResources': ");
+        exception.Message.Should().Contain($"'{typeof(KnownResourcesController).FullName}'");
+        exception.Message.Should().Contain($"'{typeof(DuplicateKnownResourcesController).FullName}'");
     }
 }