GetCustomAttributes throws Exception when attribute contains a type defined in a dynamic assembly.

[ceresgalax]

Description

When GetCustomAttributes<T>() is called on a type defined in a dynamic assembly created with AssemblyBuilder which has a custom attribute referencing another type in the dynamic assembly, a System.IO.FileNotFoundException exception is thrown.

Also note that when adding a Resolve callback to the AppDomain or ApplicationLoadContext and returning the AssemblyBuilder that contains the dynamic assembly, an exception will be thrown: System.InvalidOperationException: Dynamically emitted assemblies are unsupported during host-based resolution., so this is not a possible workaround.

Reproduction Steps

using System.Reflection;
using System.Reflection.Emit;

namespace ReproDAGetCustomAttributes;

[AttributeUsage(AttributeTargets.Class)]
public class MyCustomAttribute(Type type) : Attribute
{
    private readonly Type _type = type;
}

public static class Entry
{
    public static void Main()
    {
        AssemblyName an = new("MyDnamicAssembly");
        AssemblyBuilder ab = AssemblyBuilder.DefineDynamicAssembly(an, AssemblyBuilderAccess.RunAndCollect);
        ModuleBuilder mb = ab.DefineDynamicModule(an.Name!);
        
        TypeBuilder typeABuilder = mb.DefineType("TypeA", TypeAttributes.Class | TypeAttributes.Public);
        Type typeA = typeABuilder.CreateType();

        TypeBuilder typeBBuilder = mb.DefineType("TypeB", TypeAttributes.Class | TypeAttributes.Public);
        CustomAttributeBuilder cab = new(typeof(MyCustomAttribute).GetConstructor([typeof(Type)])!, [typeA]);
        typeBBuilder.SetCustomAttribute(cab);
        Type typeB = typeBBuilder.CreateType();
        
        typeB.GetCustomAttributes<MyCustomAttribute>(); // Throws exception
    }
}

Expected behavior

typeB.GetCustomAttributes should not throw an exception, and should return an instance of MyCustomAttribute constructed with the type of TypeA from the dynamic assembly.

Actual behavior

An exception is thrown when attempting to get the custom attributes of TypeB:

System.IO.FileNotFoundException: Could not load file or assembly 'MyDnamicAssembly, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'. The system cannot find the file specified.
File name: 'MyDnamicAssembly, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
   at System.Reflection.RuntimeAssembly.InternalLoad(AssemblyName assemblyName, StackCrawlMark& stackMark, AssemblyLoadContext assemblyLoadContext, RuntimeAssembly requestingAssembly, Boolean throwOnFileNotFound)
   at System.Reflection.TypeNameParser.ResolveAssembly(String assemblyName)
   at System.Reflection.TypeNameParser.GetType(String typeName, ReadOnlySpan`1 nestedTypeNames, String assemblyNameIfAny)
   at System.Reflection.TypeNameParser.Parse()
   at System.Reflection.TypeNameParser.GetTypeHelper(Char* pTypeName, RuntimeAssembly requestingAssembly, Boolean throwOnError, Boolean requireAssemblyQualifiedName)
   at System.Reflection.CustomAttribute._CreateCaObject(RuntimeModule pModule, RuntimeType type, IRuntimeMethodInfo pCtor, Byte** ppBlob, Byte* pEndBlob, Int32* pcNamedArgs)
   at System.Reflection.CustomAttribute.AddCustomAttributes(ListBuilder`1& attributes, RuntimeModule decoratedModule, Int32 decoratedMetadataToken, RuntimeType attributeFilterType, Boolean mustBeInheritable, ListBuilder`1 derivedAttributes)
   at System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeType type, RuntimeType caType, Boolean inherit)
   at System.Attribute.GetCustomAttributes(MemberInfo element, Type attributeType, Boolean inherit)
   at System.Reflection.CustomAttributeExtensions.GetCustomAttributes[T](MemberInfo element)
   at ReproDAGetCustomAttributes.Entry.Main()

Regression?

No response

Known Workarounds

No response

Configuration

Tested with .NET 8.0.0, & 8.0.1
Windows 10 (x64) & macOS 14.3.1 (23D60) (ARM64)

Other information

No response

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[buyaa-n]

Closing as duplicate of #95829

The solution is discussed on the issue, look #95829 (comment) for example.

[ceresgalax]

Thank you for directing me to that issue.

Unfortunately, using AppDomain.CurrentDomain.AssemblyResolve is not a solution for me, since I am defining my dynamic assembly into a collectible AssemblyLoadContext. Here is an example:

AssemblyLoadContext alc = new AssemblyLoadContext(name: null, isCollectible: true);
AssemblyBuilder ab;
Type typeB;

using (_currentAssemblyLoadContext.EnterContextualReflection()) 
{
    AssemblyName an = new("MyDnamicAssembly");
    ab = AssemblyBuilder.DefineDynamicAssembly(an, AssemblyBuilderAccess.RunAndCollect);
    ModuleBuilder mb = ab.DefineDynamicModule(an.Name!);
        
    TypeBuilder typeABuilder = mb.DefineType("TypeA", TypeAttributes.Class | TypeAttributes.Public);
    Type typeA = typeABuilder.CreateType();

    TypeBuilder typeBBuilder = mb.DefineType("TypeB", TypeAttributes.Class | TypeAttributes.Public);
    CustomAttributeBuilder cab = new(typeof(MyCustomAttribute).GetConstructor([typeof(Type)])!, [typeA]);
    typeBBuilder.SetCustomAttribute(cab);
    typeB = typeBBuilder.CreateType();
}

AppDomain.CurrentDomain.AssemblyResolve += (sender, args) => 
{
    return args.Name == ab.FullName ? ab : null;
};

typeB.GetCustomAttributes<MyCustomAttribute>(); // Throws exception

In this example, the exception thrown is:
System.NotSupportedException: Resolving to a collectible assembly is not supported.

I am using a collectible AssemblyLoadContext so that I can re-create this dynamic assembly during runtime and unload the prior dynamic assembly after a new one is created.

I'd expect GetCustomAttributes to be able to use AssemblyLoadContext.CurrentContextualReflectionContext to find the dynamic assembly. I'm not aware of any workarounds for this.

[jkotas]

This looks like a bug to me that we should fix. It should just work, without any workarounds.

[buyaa-n]

Unfortunately, using AppDomain.CurrentDomain.AssemblyResolve is not a solution for me, since I am defining my dynamic assembly into a collectible AssemblyLoadContext. Here is an example:

Ah, thank you for the example, debugging the sample code shows that RuntimeAssemblyBuilder loads the correct (CurrentContextualReflectionContext). I suspect the issue in the AssemblyLoader not in reflection emit

runtime/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeAssemblyBuilder.cs

Lines 57 to 58 in 71f8fb6

	AssemblyLoadContext? assemblyLoadContext =
	AssemblyLoadContext.CurrentContextualReflectionContext ?? AssemblyLoadContext.GetLoadContext(callingAssembly);

@elinor-fung could you take a look and change the area if needed?