[API Compat] AttributeDifference is reported when same attribute appears multiple times with different ctor args

[safern]

Take the following values:

Left:

[UnsupportedOS("browser")]
public class Foo
{
}

Right:

[UnsupportedOS("browser")]
[UnsupportedOS("ios")]
public class Foo
{
}

We would get an error:

error : CannotChangeAttribute : Attribute 'System.Runtime.Versioning.UnsupportedOSPlatformAttribute' on 'System.Net.Http.HttpClientHandler.Send(System.Net.Http.HttpRequestMessage, System.Threading.CancellationToken)' changed from '[UnsupportedOSPlatformAttribute("browser")]' in the contract to '[UnsupportedOSPlatformAttribute("browser")]' in the implementation.

There should be no error here.

The problem seems to be as we group attributes by constructor documentation ID, and then when comparing the groups, we noticed the right group has 2 entries and the left 1, and thus it is marked as changed:

arcade/src/Microsoft.Cci.Extensions/Mappings/AttributesMapping.cs

Line 43 in 7f52af2

var attrGroups = attributes.GroupBy(c => c.Constructor.DocId());

And we always use the first attribute on the group for the error string:

arcade/src/Microsoft.DotNet.ApiCompat/src/Rules/Compat/AttributeDifference.cs

Lines 144 to 145 in 7f52af2

	string contractKey = attributeComparer.GetKey(group[0].Attributes.First());
	string implementationKey = attributeComparer.GetKey(group[1].Attributes.First());

cc: @ericstj @steveisok

[eriawan]

@safern

Is this problem solved?
I think this caused my PR to fail during CI checks: dotnet/runtime#120716
Could you also confirm if this issue is related to the failure of the CI?

Also looking at the code mention in your post, the ApiCompat is not available in dotnet/arcade repo anymore, and it is available on dotnet/sdk repo:
https://github.com/dotnet/sdk/tree/main/src/Compatibility/ApiCompat

And Microsoft.Cci is not maintained anymore:
https://github.com/dotnet/arcade/blob/0af68254d65840a57e3f722e8b8c13e73edba2bd/src/Microsoft.Cci.Extensions/README.md

My next questions are:

1. Should this issue to be moved to dotnet/sdk?
2. If my failing build on my PR is caused by this issue. I would love to solve this in ApiCompat code in dotnet/sdk, but then the code has changed a lot, could you give me starting hint to solve this?

Please confirm and thank you in advance!

[safern]

Hi! I think @ViktorHofer shoudl be able to help you here as I've transferred roles.

[ViktorHofer]

Yes, we removed the legacy APICompat tooling so this issue can be closed. Unfortunately, this issue still exists in the new tooling that lives in dotnet/sdk and which is used in dotnet/runtime. dotnet/sdk#35542