CompilerGeneratedAttribute excludes new class

[cheesi]

Hello!

We have a strange issue in our project.

We added a new class that basically looks like this:

using MediatR;
using System.Transactions;
using ORG.PROJECT.OTHERPACKAGE;

namespace ORG.PROJECT.PACKAGE.Behaviours;

public class TransactionBehaviour<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>, ITransactionCommand
{
    public async Task<TResponse> Handle(
        TRequest request,
        RequestHandlerDelegate<TResponse> next,
        CancellationToken cancellationToken)
    {
        using (var scope = new TransactionScope(
            TransactionScopeOption.Required,
            new TransactionOptions { IsolationLevel = request.TransactionIsolationLevel },
            TransactionScopeAsyncFlowOption.Enabled
            ))
        {
            var result = await next();
            scope.Complete();
            return result;
        }
    }
}

This new class (&method) does not show up in our code coverage report:

I also already ruled out any display or converting issues (report generator), it is definitely already missing in the opencover file, we get from our build.

However, all other classes from that package are found. The strange thing is, that our other Behaviours classes are really similar. Like same generics, same method definition and so on. The only difference would be our ITransactionCommand interface, but also already tried removing that.

After some digging I found out, that this class gets excluded with the CompilerGeneratedAttribute

Our test execution looks like this:

- task: DotNetCoreCLI@2
  displayName: Test application
  inputs:
    command: test
    projects: '**/*Tests/*.csproj'
    arguments: >-
      --configuration $(buildConfiguration)
      --collect:"XPlat Code Coverage"
      -- DataCollectionRunSettings.DataCollectors.DataCollector.Configuration.Format=opencover
      -- DataCollectionRunSettings.DataCollectors.DataCollector.Configuration.ExcludeByFile=**/Migrations/*.cs
      -- DataCollectionRunSettings.DataCollectors.DataCollector.Configuration.ExcludeByAttribute=Obsolete,GeneratedCodeAttribute,CompilerGeneratedAttribute

As soon as I remove the CompilerGeneratedAttribute from the ExcludedByAttribute list, the new class gets detected.

Our environment:

• .NET 7.0.2
• Microsoft.NET.Test.Sdk 17.4.1
• xunit 2.4.2
• xunit.runner.visualstudio 2.4.5
• coverlet.collector 3.2.0
• Ubuntu 22.04

This looks like a bug to me and to be honest, I have zero clue, why it is behaving in that way.
Some differences to our other behaviours:

• Dependency to System.Transactions
• using statement for IDisposable
• Only this one Handle method, instead of multiple methods (that are called by the Handle method)

Apparently this was already a problem in the past: #794

If needed, I can try to create a minimal reproducible repo.

[cheesi]

I create a small reproducible repo here: https://github.com/cheesi/coverlet-issue-1437

I also checked in the two generated coverage results, one with the CompilerGeneratedAttribute and one without it.

Command:
dotnet test --configuration Release --collect:"XPlat Code Coverage" -- DataCollectionRunSettings.DataCollectors.DataCollector.Configuration.Format=opencover -- DataCollectionRunSettings.DataCollectors.DataCollector.Configuration.ExcludeByFile=**/Migrations/*.cs -- DataCollectionRunSettings.DataCollectors.DataCollector.Configuration.ExcludeByAttribute=Obsolete,GeneratedCodeAttribute,CompilerGeneratedAttribute

[daveMueller]

@cheesi Thanks a lot for the repro, as this makes it much easier for us 🙏 . We will take a look asap.

[daveMueller]

OK I analyzed this today and this is the correct behaviour if excluded by CompilerGeneratedAttribute. Every async state machine (generated class by roslyn compiler for async methods) has this attribute. In your case the whole class TransactionBehaviour is being skipped because it only has one method (for which roslyn generates the async state machine).

For instance if you leave the CompilerGeneratedAttribute and add another non-async method to the class, the class isn't skipped anymore. Although the async method Handle is still skipped. You can also see it in this issue #794 (comment).

[cheesi]

Hey @daveMueller !

Thank you very much for your help!

So the suggested way is to remove the CompilerGeneratedAttribute from the ExcludeByAttribute? Won't this have any other unwanted implications?

[daveMueller]

Yes I would advise to remove it. Only thing that I have in mind are auto-implemented properties that after removing could be reported as uncovered (instead of beeing skipped). But therefore there is the SkipAutoProps option (https://github.com/coverlet-coverage/coverlet/blob/master/Documentation/MSBuildIntegration.md#skip-auto-implemented-properties).

@petli @MarcoRossignoli @tonerdo Any other thoughts on this?

[MarcoRossignoli]

We cannot do a lot for it as @daveMueller explained, I also suggest to remove the attribute and handle the "noise" with other filtering.

[cheesi]

Alright, thanks for your help guys!