Read parameters of attribute created by source generator

I have the following source code generator

[Generator]
public class Generator : ISourceGenerator
{
    public void Execute(GeneratorExecutionContext context)
    {
        var output = @"using System;
namespace SourceGeneratorAttributes;
[AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
class GlobalAttribute : Attribute
{
    public int OptionalNumber { get; set; } = 10;
    public string OptionalString { get; set; } = ""test"";
    public GlobalAttribute(string requiredString, int requiredNumber) {}
}
";
        context.AddSource("GlobalAttribute.cs", SourceText.From(output, Encoding.UTF8));

        var attributes = context.Compilation.Assembly.GetAttributes();
        foreach (var attribute in attributes)
        {
            Console.WriteLine(attribute);
        }
    }
    public void Initialize(GeneratorInitializationContext context)
    {
    }
}

Then in the project where I use the source generator I have the following

[assembly:Global("text", 20, OptionalNumber = 33, OptionalString = "random")]

But if I break on Console.WriteLine(attribute); and inspect the attribute I get the following:

How do I find what the error is? and why are all arguments gone?

If I use a different attribute like AssemblyFileVersion then I can read the arguments as expected.

Full code can be found here: https://github.com/AnderssonPeter/SourceGeneratorAttributes

You have to create a separate class that has the Generator attribute that implements the IIncrementalGenerator and uses RegisterPostInitializationOutput to add the attribute

Example:

[Generator]
public class AttributeGenerator : IIncrementalGenerator
{
    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        context.RegisterPostInitializationOutput(i =>
        {
            i.AddSource("GlobalParameterAttribute.g.cs", @"using System;
namespace SourceGeneratorAttributes;
[AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
public sealed class GlobalParameterAttribute : Attribute
{
    public int OptionalNumber { get; set; } = 10;
    public string OptionalString { get; set; } = ""test"";
    public GlobalParameterAttribute(string requiredString, int requiredNumber) {}
}");
        });

    }
}

Then you can use it in your normal generator like so

[Generator]
public class Generator : ISourceGenerator
{
    public void Execute(GeneratorExecutionContext context)
    {
        var attributes = context.Compilation.Assembly.GetAttributes();
        foreach (var attribute in attributes)
        {
            Console.WriteLine(attribute);
        }
    }
    public void Initialize(GeneratorInitializationContext context)
    {
    }
}