The PipeWriter 'ResponseBodyPipeWriter' does not implement PipeWriter.UnflushedBytes

[vsfeedback]

This issue has been moved from a ticket on Developer Community.

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Microsoft Visual Studio Enterprise 2022 (64-bit) - Preview
Version 17.12.0 Preview 2.0
Solution: Minimal Web Api and Xunit (.NET 9.0.0-rc.1.24431.7)
WebApiXunit3.zip
The error:
The PipeWriter ‘ResponseBodyPipeWriter’ does not implement PipeWriter.UnflushedBytes

The same code works fine in .NET 8

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Original Comments

Feedback Bot on 9/18/2024, 00:30 AM:

We have directed your feedback to the appropriate engineering team for further evaluation. The team will review the feedback and notify you about the next steps.

Feedback Bot on 9/19/2024, 02:55 AM:

Thank you for sharing your feedback! Our teams prioritize action on product issues with broad customer impact. See details at: https://docs.microsoft.com/en-us/visualstudio/ide/report-a-problem#faq. In case you need answers to common questions or need assisted support, be sure to use https://visualstudio.microsoft.com/vs/support/. We’ll keep you posted on any updates to this feedback.

[mkArtakMSFT]

@BrennanConroy FYI

[BrennanConroy]

Update your Microsoft.AspNetCore.Mvc.Testing reference.

[Megasoft2]

Hi @BrennanConroy .

Now it works! with Microsoft.AspNetCore.Mvc.Testing 9.0.0-rc.1.24452.1

Thank you so much
Sincerely
Jorge

[WernerMairl]

same situation here: got the exception => update to 9.0.0-rc.1.24452.1 => solved!
BR
Werner

[erenken]

Unfortunately this didn't help me. I have a .NET 8 API project I wanted to convert to 9 and I get this error in my tests. I have tried the specific version and the release version of 9.0.0 and I still get the error. I have verified there aren't any nuget updates for this release or preview.

I did notice that I had to manually add Microsoft.Extensions.Caching.Memory with version 9.0.0 as something was still pointing to the pre-release version of it and it has a known vulnerability. I also see under Framework that it shows Microsoft.NETCore.App with version 9.0.0-rc.2.24473.5. I figure that should also not be an RC.

I guess for now I will stick with .NET 8.

This is what my CSPROJ looks like.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net9.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <IsPackable>false</IsPackable>
    <IsTestProject>true</IsTestProject>
  </PropertyGroup>
  <ItemGroup>
    <None Remove="appsettings.json" />
  </ItemGroup>
  <ItemGroup>
    <Content Include="appsettings.json">
      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
      <ExcludeFromSingleFile>true</ExcludeFromSingleFile>
      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
    </Content>
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="coverlet.collector" Version="6.0.2">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="9.0.0" />
    <PackageReference Include="Microsoft.Extensions.Caching.Memory" Version="9.0.0" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
    <PackageReference Include="MSTest.TestAdapter" Version="3.6.3" />
    <PackageReference Include="MSTest.TestFramework" Version="3.6.3" />
    <PackageReference Include="NSubstitute" Version="5.3.0" />
    <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.10.0" />
    <PackageReference Include="OpenTelemetry.Instrumentation.SqlClient" Version="1.9.0-beta.1" />
  </ItemGroup>
  <ItemGroup>
    <ProjectReference Include="..\..\src\MY.API\MY.API.csproj" />
  </ItemGroup>
  <ItemGroup>
    <Using Include="Microsoft.VisualStudio.TestTools.UnitTesting" />
  </ItemGroup>
  <ItemGroup>
    <Folder Include="OpenTelemetry\" />
  </ItemGroup>
</Project>

[craigb]

This seems to be a breaking change when running net6 and net8 test code against the net9 runtime. Is that expected? I didn't see it called out in the NET9 release notes. I put a repro up at https://github.com/craigb/pipewriter-repro -- when you set RollForward to LatestMajor, it will use the net9 runtime and the code will break.

[davidfowl]

That makes sense. .NET 9's JSON implementation relies on PipeWriter.UnflushedBytes.'s implementation. We should just document this breaking change if we haven't.

cc @Priya91 @eiriktsarpalis