Calling AddMediatRIncludingLibraries without any registered assemblie…

…s should not throw

Build.ps1

@@ -0,0 +1,35 @@
+# Taken from psake https://github.com/psake/psake
+
+<#
+.SYNOPSIS
+  This is a helper function that runs a scriptblock and checks the PS variable $lastexitcode
+  to see if an error occcured. If an error is detected then an exception is thrown.
+  This function allows you to run command-line programs without having to
+  explicitly check the $lastexitcode variable.
+.EXAMPLE
+  exec { svn info $repository_trunk } "Error executing SVN. Please verify SVN command-line client is installed"
+#>
+function Exec
+{
+    [CmdletBinding()]
+    param(
+        [Parameter(Position=0,Mandatory=1)][scriptblock]$cmd,
+        [Parameter(Position=1,Mandatory=0)][string]$errorMessage = ($msgs.error_bad_command -f $cmd)
+    )
+    & $cmd
+    if ($lastexitcode -ne 0) {
+        throw ("Exec: " + $errorMessage)
+    }
+}
+
+$artifacts = ".\artifacts"
+
+if(Test-Path $artifacts) { Remove-Item $artifacts -Force -Recurse }
+
+exec { & dotnet clean -c Release }
+
+exec { & dotnet build -c Release }
+
+exec { & dotnet test -c Release -r $artifacts --no-build -l trx --verbosity=normal }
+
+exec { dotnet pack .\src\MediatR.Extensions.Microsoft.DependencyInjection.Libraries -c Release -o $artifacts --no-build }

src/MediatR.Extensions.Microsoft.DependencyInjection.Libraries/Ext/ServiceCollectionEx.cs

@@ -59,7 +59,12 @@ public static IServiceCollection AddMediatRIncludingLibraries(this IServiceColle
             var isMediatRAlreadyRegistered = serviceCollection.Any(c => c.ServiceType == typeof(IMediator));
             if (isMediatRAlreadyRegistered) throw new Exception($"MediatR is already registered in the container. {nameof(AddMediatRIncludingLibraries)} can not run.");
 
-            return serviceCollection.AddMediatR(MediatRLibraryRegistrar.GetAssemblies().ToArray(), MediatRLibraryRegistrar.GetConfigurationActions());
+            // If there aren't any assemblies registered, then don't add Mediator as it will error. "No assemblies found to scan. Supply at least one assembly to scan for handlers."
+            var assembliesToScan = MediatRLibraryRegistrar.GetAssemblies().ToArray();
+            if (assembliesToScan.Any())
+                return serviceCollection
+                    .AddMediatR(assembliesToScan, MediatRLibraryRegistrar.GetConfigurationActions());
+            return serviceCollection;
         }
     }
 }

test/MediatR.Extensions.Microsoft.DependencyInjection.Libraries.Tests/MediatRLibraryRegistrarTests.cs

@@ -152,6 +152,17 @@ public void AddMediatRIncludingLibraries_when_Mediatr_already_registered_should_
             Assert.Contains("already registered", exception.Message);
         }
 
-
+        [Fact]
+        public void Calling_AddMediatRIncludingLibraries_without_any_registered_assemblies_should_not_throw()
+        {
+            // ARRANGE
+            var serviceCollection = new ServiceCollection();
+
+            // ACT
+            var exception = Record.Exception(() => serviceCollection.AddMediatRIncludingLibraries());
+
+            // ASSSERT
+            Assert.Null(exception);
+        }
     }
 }