Fix attribute loading for cases where the base class is not available

ArchUnit.sln

@@ -46,7 +46,7 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ArchUnitNET.TUnitTests", "A
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "InterfaceAssembly", "TestAssemblies\InterfaceAssembly\InterfaceAssembly.csproj", "{076E223C-32D3-4672-8B00-925CDBC1383E}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "FilteredDirectoryAssemblyAttributeAssembly", "TestAssemblies\FilteredDirectoryAssemblyAttributeAssembly\FilteredDirectoryAssemblyAttributeAssembly.csproj", "{AA695589-8CCC-4474-9A7F-01A6376C375A}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "FilteredDirectoryUnavailableTypesAssembly", "TestAssemblies\FilteredDirectoryUnavailableTypesAssembly\FilteredDirectoryUnavailableTypesAssembly.csproj", "{AA695589-8CCC-4474-9A7F-01A6376C375A}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution

ArchUnitNET/Loader/MonoCecilAttributeExtensions.cs

@@ -21,9 +21,12 @@ TypeFactory typeFactory
                 attributeTypeReference
             );
             var attribute = attributeType.Type as Attribute;
-            if (attributeType.Type is UnavailableType unavailableType)
+            if (
+                attribute == null
+                && (attributeType.Type is UnavailableType || attributeType.Type is Class)
+            )
             {
-                attribute = new Attribute(unavailableType, null, null);
+                attribute = new Attribute(attributeType.Type, null, null);
             }
             if (attribute == null)
             {

ArchUnitNETTests/Loader/ArchLoaderTests.cs

@@ -149,7 +149,7 @@ public void UnavailableTypeTest()
                     System.IO.SearchOption.AllDirectories
                 )
                 .Build();
-            Assert.Single(architecture.Types);
+            Assert.Equal(3, architecture.Types.Count());
             var loggerType = architecture.ReferencedTypes.WhereFullNameIs("Serilog.ILogger");
             Assert.NotNull(loggerType);
             Assert.True(loggerType is UnavailableType);

TestAssemblies/FilteredDirectoryLoaderTestAssembly/Class1.cs

@@ -1,6 +1,7 @@
+using FilteredDirectoryUnavailableTypesAssembly;
 using Serilog;
 
-[assembly: FilteredDirectoryAssemblyAttributeAssembly.AssemblyAttribute]
+[assembly: Assembly]
 
 namespace FilteredDirectoryLoaderTestAssembly;
 
@@ -13,3 +14,8 @@ public Class1()
         this.logger = new LoggerConfiguration().CreateLogger();
     }
 }
+
+public class DerivedAttribute : BaseAttribute { }
+
+[Derived]
+public class ClassWithDerivedAttribute { }

TestAssemblies/FilteredDirectoryLoaderTestAssembly/FilteredDirectoryLoaderTestAssembly.csproj

@@ -11,7 +11,7 @@
     <PackageReference Include="Serilog.Sinks.Console" Version="6.0.0" />
   </ItemGroup>
   <ItemGroup>
-    <ProjectReference Include="..\FilteredDirectoryAssemblyAttributeAssembly\FilteredDirectoryAssemblyAttributeAssembly.csproj">
+    <ProjectReference Include="..\FilteredDirectoryUnavailableTypesAssembly\FilteredDirectoryUnavailableTypesAssembly.csproj">
       <!-- Do not copy the referenced assembly to the output directory -->
       <!-- in order to test handling of unavailable types as attribute assemblies -->
       <Private>False</Private>

TestAssemblies/FilteredDirectoryAssemblyAttributeAssembly/FilteredDirectoryAssemblyAttributeAssembly.csproj → TestAssemblies/FilteredDirectoryUnavailableTypesAssembly/FilteredDirectoryUnavailableTypesAssembly.csproj

@@ -4,5 +4,6 @@
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <IsPackable>false</IsPackable>
+    <RootNamespace>FilteredDirectoryUnavailableTypesAssembly</RootNamespace>
   </PropertyGroup>
 </Project>

TestAssemblies/FilteredDirectoryUnavailableTypesAssembly/UnavailableTypes.cs

@@ -0,0 +1,7 @@
+namespace FilteredDirectoryUnavailableTypesAssembly;
+
+[AttributeUsage(AttributeTargets.Assembly)]
+public class AssemblyAttribute : Attribute { }
+
+[AttributeUsage(AttributeTargets.All)]
+public class BaseAttribute : Attribute { }