How to add new attributes at the assembly level?

[batzen]

Hi there,

we are currently using PostSharp to add custom attributes at the assembly level.
I couldn't figure out how to do this using MetaLama.

How can i achieve this? Or this not yet supported?

[prochan2]

Hi,

In Metalama, this is done using Fabrics. See https://doc.metalama.net/fabrics/fabrics-aspects .

[batzen]

To clarify i want to add attributes like

[assembly: MyAttribute("SomeData")]

How is that possible with a Fabric?

[batzen]

Ok. I was able to add attributes.
But now i am encountering a new issue.

Using sample works when building locally, but trying to use the commented variant (using the type instead of it's name) fails with

Metalama Version: 0.5.36-preview
Runtime: .NET 6.0.7
Processor Architecture: X64
OS Description: Microsoft Windows 10.0.19042
OS Architecture: X64
Exception type: System.InvalidOperationException
Exception message: Cannot find the reference 'Metalama.Framework.Engine.4.0.1, Version=0.5.36.0, Culture=neutral, PublicKeyToken=772fca7b1db8db06' in project 'MetaTest'.
===== Exception ===== 
System.InvalidOperationException: Cannot find the reference 'Metalama.Framework.Engine.4.0.1, Version=0.5.36.0, Culture=neutral, PublicKeyToken=772fca7b1db8db06' in project 'MetaTest'.
   at Obfuscated.^_JBWn79oGUOC.^8m4_iz7VnhTf(String _0, AssemblyName _1)
   at Obfuscated.^_JBWn79oGUOC.^jycO54BV(Type _0, Type[] _1)
   at Obfuscated.^_JBWn79oGUOC.^UoM_QPsJ(Type _0)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Metalama.Framework.Engine.CodeModel.DeclarationFactory.GetTypeByReflectionType(Type type)
   at Metalama.Framework.Code.TypeFactory.GetType(Type type)
   at Metalama.Framework.Code.ConstructorCollectionExtensions.<OfCompatibleSignature>g__GetParameter|0_0(ValueTuple`2 context, Int32 index)
   at Metalama.Framework.Code.SignatureMatcher.<OfCompatibleSignature>g__IsMatchingParameter|0_0[TMember,TPayload](ValueTuple`3 payload, Int32 parameterIndex, IType expectedType, RefKind expectedRefKind)
   at Metalama.Framework.Code.SignatureMatcher.OfSignature[TMember,TPayload](IMemberCollection`1 members, TPayload payload, String name, Nullable`1 parameterCount, Func`5 parameterPredicate, Nullable`1 isStatic, Boolean expandParams)+MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Metalama.Framework.Code.DeclarationBuilders.AttributeConstruction.Create(INamedType attributeType, IReadOnlyList`1 constructorArguments, IReadOnlyList`1 namedArguments)
   at Metalama.Framework.Code.DeclarationBuilders.AttributeConstruction.Create(Type attributeType, IReadOnlyList`1 constructorArguments, IReadOnlyList`1 namedArguments)
   at MetaTest.MyAspect.BuildAspect(IAspectBuilder`1 builder) in C:\Users\b.schmidt\AppData\Local\Temp\Metalama\CompileTime\MetaTest\.netcoreapp6.0\c30c65ad7c6c6cf8\4.2.1011-preview\TestFile_cce0c07020294db1.cs:line 21
   at Obfuscated.^64I0ULpJ_QNn.^OxsIJ1oM.^1b5bui6R()
   at Obfuscated.^AJY78_gCSvfx.^NpOkTBic.^C8puhBFL()
   at Obfuscated.^AJY78_gCSvfx.^kAku[??0,??1](UserCodeFunc`2 _0, ??1& _1, ^5ubseQzw8kM2 _2)
   at Obfuscated.^AJY78_gCSvfx.^kAku[??0](Func`1 _0, ^5ubseQzw8kM2 _1)
   at Obfuscated.^AJY78_gCSvfx.^Tw_fYFAI[??0](Func`1 _0, ^5ubseQzw8kM2 _1, ??0& _2)
   at Obfuscated.^AJY78_gCSvfx.^Tw_fYFAI(Action _0, ^5ubseQzw8kM2 _1)
   at Obfuscated.^64I0ULpJ_QNn.^dts0rUh1[??0](??0 _0, String _1, ^U1hN_NLZi03Z _2, CompilationModel _3, CompilationModel _4, AspectPipelineConfiguration _5, CancellationToken _6)
   at Obfuscated.^64I0ULpJ_QNn.^OHjxIW81(^U1hN_NLZi03Z _0, String _1, CompilationModel _2, CompilationModel _3, AspectPipelineConfiguration _4, CancellationToken _5)
   at Obfuscated.^v6_QT0k7g1m2.^9FbDLjcf(IEnumerable`1 _0, CompilationModel _1, Action`1 _2, CancellationToken _3)
   at Obfuscated.^v6_QT0k7g1m2.^46Z9(CompilationModel _0, CancellationToken _1)
   at Obfuscated.^JPhCEiV5epPJ.^46Z9(CancellationToken _0)
   at Obfuscated.^mjGX9Ib2unuR.^_w6byyh5(AspectPipelineConfiguration _0, AspectPipelineResult _1, IDiagnosticAdder _2, CancellationToken _3, AspectPipelineResult& _4)
   at Metalama.Framework.Engine.Pipeline.AspectPipeline.^_w6byyh5(PartialCompilation _0, CompilationModel _1, IDiagnosticAdder _2, AspectPipelineConfiguration _3, CancellationToken _4, AspectPipelineResult& _5)
   at Metalama.Framework.Engine.Pipeline.CompileTime.CompileTimeAspectPipeline.ExecuteCoreAsync(IDiagnosticAdder diagnosticAdder, PartialCompilation compilation, ImmutableArray`1 resources, AspectPipelineConfiguration configuration, CancellationToken cancellationToken)
   at Metalama.Framework.Engine.Pipeline.CompileTime.CompileTimeAspectPipeline.ExecuteAsync(IDiagnosticAdder diagnosticAdder, Compilation compilation, ImmutableArray`1 resources, CancellationToken cancellationToken)

[prochan2]

I'm sorry for misunderstanding your question. You can also add a custom attribute to an assembly without applying an aspect to a type:

[assembly:MyAspect]

public class MyAspect : CompilationAspect
{
    public override void BuildAspect(IAspectBuilder<ICompilation> builder)
    {
        builder.Advice.IntroduceAttribute(builder.Target, AttributeConstruction.Create(typeof(MyAttribute), new object?[] { "compilation" }));
    }
}

We'll have a closer look at the exception.

[batzen]

Thanks for the CompilationAspect tip. That will be helpful.
And thanks for having a look at the exception.
Should i create an issue for that?

[prochan2]

No need to create an issue, thank you. It's fixed now and we'll notify you as soon as the fix is released.

[gfraiteur]

The bug is when you are using typeof because Metalama now expects an IType instead of a System.Type. You can get an IType from a System.Type by using the TypeFactory class.

[batzen]

Neither System.Type nor IType work for AttributeConstruction.
I might misunderstand your answer.
Could you provide a sample of how to use type parameters as attribute ctor parameters for attribute construction?

I am trying to create attributes of this form:

public class MyAttribute : Attribute
{   
    public MyAttribute(Type value, Type value1)
    {
    }
}

Neither var attributeConstruction = AttributeConstruction.Create(typeof(MyAttribute), new object?[] { exportType, type }); nor
var attributeConstruction = AttributeConstruction.Create(typeof(MyAttribute), new object?[] { TypeFactory.GetType(exportType), TypeFactory.GetType(type) }); work.
Both throw an exception.

[gfraiteur]

I'm sorry, you are right. I believed this was covered by unit tests but it seems that it does not work in practice.
The bug is filed and we will ping you when it will be fixed. It is taking more time because of vacation.

[batzen]

No worries. Vacations are important.
Metalama is in preview and i expected to encounter issues, but i was already able to migrate some of our PostSharp aspects to a test project. The new code and our compile should be way faster after a complete migration.

Congratulations for that. What you/your team has achieved is what I always dreamt of when Roslyn was released.

[addabis]

We have released Metalama 0.5.37-preview, which fixes one part of this issue.

You can now pass IType to AttributeConstruction.Create's parameters.

Using System.Reflection.Type is not possible at the moment. You have to manually call TypeFactory.GetType to convert to IType.

[batzen]

Works like a charm.
Thanks for the quick fix!

[gfraiteur]

In 0.5.38, you should be able to pass a System.Type.

[batzen]

@gfraiteur I just tested 0.5.40 and passing System.Type does not work while TypeFactory.GetType does work.

[gfraiteur]

What code exactly fails and what is the exception message?

We now have a unit test for this case:

using System;
using Metalama.Framework.Aspects;
using Metalama.Framework.Code;
using Metalama.Framework.Code.DeclarationBuilders;

namespace Metalama.Framework.Tests.Integration.Tests.Aspects.Attributes.AddWithParameterOfType;

public class MyAttribute : Attribute 
{
    public MyAttribute(Type t)
    {
    }
}

public class MyAspect : MethodAspect
{
    public override void BuildAspect(IAspectBuilder<IMethod> builder)
    {
        builder.Advice.IntroduceAttribute(
            builder.Target, 
            AttributeConstruction.Create(
                typeof(MyAttribute),
                constructorArguments: new object?[] { typeof(C) }));
    }
}

// <target>
internal class C
{
    [MyAspect]
    private void M() { }
}

[batzen]

It's still the same exception as before.
Repro

[gfraiteur]

Thank you. I will investigate more. It seems to be a condition that would not be reproducible using our test framework.
Note that the online sandbox hasn't been updated for a while.

[gfraiteur]

I think this has been solved a few builds ago but we forgot to mention it in this discussion.
Could you retry with a recent build please?

[batzen]

@gfraiteur I just tested 0.5.47 and passing System.Type does not work while TypeFactory.GetType does work.