Unable to check for existence of unbound generic typed attribute on type

I'm looking to build out the behavior of a Blazor component based on the attributes applied to the type:

public abstract record EditStartAction();

public sealed class CanEdit<TEditAction> : Attribute
  where TEditAction : EditStartAction, new()
{
}

public record MyCreateStartAction : CreateStartAction
{
}

[GenerateBehavior]
[CanEdit<MyCreateStartAction>]
public partial class TestTable : FluxorComponent
{
}

public sealed class GenerateBehavior : TypeAspect
{
  public override void BuildAspect(IAspectBuilder<INamedType> builder)
  {
    var supportsEditing = builder.Target.Attributes.OfAttributeType(typeof(CanEditAttribute<>)).Any();

    if (supportsEditing) 
    {
      //Introduce a method
    }
  }
}

public abstract record EditStartAction();

public sealed class CanEdit<TEditAction> : Attribute
  where TEditAction : EditStartAction, new()
{
}

public record MyCreateStartAction : CreateStartAction
{
}

[GenerateBehavior]
[CanEdit<MyCreateStartAction>]
public partial class TestTable : FluxorComponent
{
}

public sealed class GenerateBehavior : TypeAspect
{
  public override void BuildAspect(IAspectBuilder<INamedType> builder)
  {
    var supportsEditing = builder.Target.Attributes.OfAttributeType(typeof(CanEditAttribute<>)).Any();

    if (supportsEditing) 
    {
      //Introduce a method
    }
  }
}

In one of the logging examples, we do something similar with:

private static bool IsSensitive(IParameter parameter) => parameter.Attributes.OfAttributeType(typof(SensitiveDataAttribute)).Any();

private static bool IsSensitive(IParameter parameter) => parameter.Attributes.OfAttributeType(typof(SensitiveDataAttribute)).Any();

This works fine, but in my larger example above, it never shows the introduced method even though it appears to be the same thing. Am I doing something wrong or does the OfAttributeType method not handle unbound generic types in a typeof well unlike non-generic attributes? Thanks!

5 Replies

WhitOP•2y ago

Testing further, if I add an attribute without a generic type:

[AttributeUsage(AttributeTargets.Class)]
public class CanDoThingsAttribute : Attribute
{
}

[AttributeUsage(AttributeTargets.Class)]
public class CanDoThingsAttribute : Attribute
{
}

and decorate my target class accordingly:

[GenerateBehavior]
[CanEdit<MyCreateStartAction>]
[CanDoThings]
public partial class TestTable : FluxorComponent
{
}

[GenerateBehavior]
[CanEdit<MyCreateStartAction>]
[CanDoThings]
public partial class TestTable : FluxorComponent
{
}

And then update the aspect to include a check for this attrbute:

var supportsSomething = builder.Target.Attributes.Any(typeof(CanDoThingsAttribute));`

var supportsSomething = builder.Target.Attributes.Any(typeof(CanDoThingsAttribute));`

And then finally update the logic to add the method or not:

        if (supportsCreating || supportsSomething)
        {
        }

        if (supportsCreating || supportsSomething)
        {
        }

Then it works, indicating that it's an identification issue with the unbound generically typed attribute as if there's no generic type involved, it works as expected.

Gael Fraiteur•2y ago

I have filed an enhancement request. In the meantime, you should use something like this:

parameter.Attributes.Any( a => a.Type is INamedType namedType && namedType.Is( typeof(Foo<>) ) )

parameter.Attributes.Any( a => a.Type is INamedType namedType && namedType.Is( typeof(Foo<>) ) )

WhitOP•2y ago

That doesn't seem to be working either - when using:

var supportsCreating = builder.Target.Attributes.Any(a => a.Type is { } namedType && namedType.Is(typeof(CanCreateAttribute<>)));

var supportsCreating = builder.Target.Attributes.Any(a => a.Type is { } namedType && namedType.Is(typeof(CanCreateAttribute<>)));

if (supportsCreating)
{
 //Introduce method
}

if (supportsCreating)
{
 //Introduce method
}

The method is never introduced in the preview even though the attribute is attached:

[GenerateBehavior]
[CanCreate<MyCreateStartAction>]
public partial class TestTable : FluxorComponent
{
}

[GenerateBehavior]
[CanCreate<MyCreateStartAction>]
public partial class TestTable : FluxorComponent
{
}

Gael Fraiteur•2y ago

Sorry, I forgot the TypeDefinition part:

parameter.Attributes.Any( a => a.Type is INamedType namedType && namedType.TypeDefinition.Is( typeof(Foo<>) ) )

parameter.Attributes.Any( a => a.Type is INamedType namedType && namedType.TypeDefinition.Is( typeof(Foo<>) ) )

WhitOP•2y ago

That did the trick. Thank you!

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Unable to check for existence of unbound generic typed attribute on type