RawDefaultValue is resolved differently between runtimes

[ivanpovazan]

The issue

The following code gives different results when executed on different runtime flavours:

• coreCLR -> outputs: SomeOtherValue
• Mono -> outputs: SomeValue
• NativeAOT -> outputs: SomeValue

using System;
using System.Reflection;
using System.Runtime.CompilerServices;

public class Program
{
    internal abstract class UsableCustomConstantAttribute : CustomConstantAttribute
    {
        public sealed override object Value => RealValue;
        protected object RealValue { get; set; }
    }

    private class StringCustomConstantAttribute : UsableCustomConstantAttribute
    {
        public new object Value { get { return RealValue; } set { RealValue = value; } }
    }

    private class AnotherStringCustomConstantAttribute : UsableCustomConstantAttribute
    {
        public new object Value { get { return RealValue; } set { RealValue = value; } }
    }

    public void Foo([StringCustomConstant(Value = "SomeValue")] [AnotherStringCustomConstant(Value = "SomeOtherValue")] object param) { }

    static void Main()
    {
        Console.WriteLine(typeof(Program).GetMethod("Foo").GetParameters()[0].RawDefaultValue);
    }
}

Expected

All runtimes should produce the same result.

TODO

Align the implementation of RawDefaultValue resolution between runtimes.
Mono:

runtime/src/mono/System.Private.CoreLib/src/System/Reflection/RuntimeParameterInfo.cs

Line 158 in 19c5d17

object? RawDefaultValue

CoreCLR:

runtime/src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeParameterInfo.cs

Line 297 in 19c5d17

private object? GetDefaultValueInternal(bool raw)

NativeAOT:

runtime/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/General/Helpers.cs

Line 206 in 19c5d17

public static bool GetCustomAttributeDefaultValueIfAny(IEnumerable<CustomAttributeData> customAttributes, bool raw, out object? defaultValue)

---

This is related to: #49806

[ghost]

Tagging subscribers to this area: @dotnet/area-system-reflection
See info in area-owners.md if you want to be subscribed.

Issue Details

---

The issue

The following code gives different results when executed on different runtime flavours:

• coreCLR -> outputs: SomeOtherValue
• Mono -> outputs: SomeValue
• NativeAOT -> outputs: SomeValue

using System;
using System.Reflection;
using System.Runtime.CompilerServices;

public class Program
{
    internal abstract class UsableCustomConstantAttribute : CustomConstantAttribute
    {
        public sealed override object Value => RealValue;
        protected object RealValue { get; set; }
    }

    private class StringCustomConstantAttribute : UsableCustomConstantAttribute
    {
        public new object Value { get { return RealValue; } set { RealValue = value; } }
    }

    private class AnotherStringCustomConstantAttribute : UsableCustomConstantAttribute
    {
        public new object Value { get { return RealValue; } set { RealValue = value; } }
    }

    public void Foo([StringCustomConstant(Value = "SomeValue")] [AnotherStringCustomConstant(Value = "SomeOtherValue")] object param) { }

    static void Main()
    {
        Console.WriteLine(typeof(Program).GetMethod("Foo").GetParameters()[0].RawDefaultValue);
    }
}

Expected

All runtimes should produce the same result.

TODO

Align the implementation of RawDefaultValue resolution between runtimes.
Mono:

runtime/src/mono/System.Private.CoreLib/src/System/Reflection/RuntimeParameterInfo.cs

Line 158 in 19c5d17

object? RawDefaultValue

CoreCLR:

runtime/src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeParameterInfo.cs

Line 297 in 19c5d17

private object? GetDefaultValueInternal(bool raw)

NativeAOT:

runtime/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/General/Helpers.cs

Line 206 in 19c5d17

public static bool GetCustomAttributeDefaultValueIfAny(IEnumerable<CustomAttributeData> customAttributes, bool raw, out object? defaultValue)

---

This is related to: #49806

Author:	ivanpovazan
Assignees:	ivanpovazan
Labels:	area-System.Reflection, area-System.Reflection-mono, area-NativeAOT-coreclr
Milestone:	8.0.0

[ivanpovazan]

cc @jkotas

[teo-tsirpanis]

(we use only one area per issue)

[steveharter]

Like CoreClr, .NET Framework also returns "SomeOtherValue" so assuming this is the expected result, Mono and NativeAOT should be changed to return the last parameter attribute.

If we agree that is the case, then this issue should be moved to [area-System.Reflection-mono] and another tracking issue logged for NativeAOT.

This does seem like a niche issue, however, since it requires multiple parameter attributes.

[jkotas]

@steveharter Ivan is fixing this in #75612

[ivanpovazan]

Closing as completed via 05b8bab