Clean & Rebuild targets appear to calculate incorrect version when using GeneratePackageOnBuild

[MattKotsenas]

I'm not 100% sure this is a bug and not user error, but it feels like a bug, so I apologize if I've misunderstood the scenario 😊.

Repro setup

Use a simple project setup like this:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <RootNamespace>nbgv_rebuild</RootNamespace>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <IsPackable>true</IsPackable>
    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Nerdbank.GitVersioning" Version="3.6.139">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
  </ItemGroup>

  <Target Name="PrintPackageVersion" AfterTargets="_GetOutputItemsFromPack">
    <!-- Stand in for custom targets that use the package -->
    <Message Text="_OutputPackItems = @(_OutputPackItems)" Importance="High" />
  </Target>

</Project>

In my case I'm inside a git repo, but with no version.json and no commits.

Correct output

If I do a standard build like this:

dotnet clean && dotnet build /tl:off

I get output like this

Build succeeded in 0.5s
  Determining projects to restore...
  All projects are up-to-date for restore.
  nbgv-rebuild -> D:\Projects\nbgv-rebuild\bin\Debug\net8.0\nbgv-rebuild.dll
  _OutputPackItems = D:\Projects\nbgv-rebuild\bin\Debug\nbgv-rebuild.0.0.0-g.nupkg;D:\Projects\nbgv-rebuild\obj\Debug\nbgv-rebuild.0.0.0-g.nuspec
  The package nbgv-rebuild.0.0.0-g is missing a readme. Go to https://aka.ms/nuget/authoring-best-practices/readme to learn why package readmes are important.
  Successfully created package 'D:\Projects\nbgv-rebuild\bin\Debug\nbgv-rebuild.0.0.0-g.nupkg'.

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:01.24

Note the version of 0.0.0-g. That's expected given the setup.

Incorrect output

If I do a clean (or a Rebuild) like this:

dotnet clean /tl:off

I get output like this:

Build started 7/29/2024 11:58:40 AM.
     1>Project "D:\Projects\nbgv-rebuild\nbgv-rebuild.sln" on node 1 (Clean target(s)).
     1>ValidateSolutionConfiguration:
         Building solution configuration "Debug|Any CPU".
     1>Project "D:\Projects\nbgv-rebuild\nbgv-rebuild.sln" (1) is building "D:\Projects\nbgv-rebuild\nbgv-rebuild.csproj" (2) on node 1 (Clean target(s)).
       CoreClean:
         Deleting file "D:\Projects\nbgv-rebuild\bin\Debug\net8.0\nbgv-rebuild.deps.json".
         Deleting file "D:\Projects\nbgv-rebuild\bin\Debug\net8.0\nbgv-rebuild.dll".
         Deleting file "D:\Projects\nbgv-rebuild\bin\Debug\net8.0\nbgv-rebuild.pdb".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\net8.0\nbgv-rebuild.GeneratedMSBuildEditorConfig.editorconfig".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\net8.0\nbgv-rebuild.AssemblyInfoInputs.cache".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\net8.0\nbgv-rebuild.AssemblyInfo.cs".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\net8.0\nbgv-rebuild.csproj.CoreCompileInputs.cache".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\net8.0\nbgv-rebuild.dll".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\net8.0\refint\nbgv-rebuild.dll".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\net8.0\nbgv-rebuild.pdb".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\net8.0\ref\nbgv-rebuild.dll".
       PrintPackageVersion:
         _OutputPackItems = D:\Projects\nbgv-rebuild\bin\Debug\nbgv-rebuild.1.0.0.nupkg;D:\Projects\nbgv-rebuild\obj\Debug\nbgv-rebuild.1.0.0.nuspec
     2>Done Building Project "D:\Projects\nbgv-rebuild\nbgv-rebuild.csproj" (Clean target(s)).
     1>Done Building Project "D:\Projects\nbgv-rebuild\nbgv-rebuild.sln" (Clean target(s)).

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:00.51

Note that now the version of the package was 1.0.0 and that the package wasn't cleaned. I'd expect to also see this section in the output:

      _CleanPackageFiles:
         Deleting file "D:\Projects\nbgv-rebuild\bin\Debug\nbgv-rebuild.0.0.0-g.nupkg".
         Deleting file "D:\Projects\nbgv-rebuild\obj\Debug\nbgv-rebuild.0.0.0-g.nuspec".

but I don't.

My (likely incorrect) diagnosis

It seems that nbgv isn't hooking into Clean targets correctly and thus the default and incorrect version is being used.

[MattKotsenas]

I'm happy to pursue a fix here if desired, but wanted to validate that I correctly understand the expected behavior before digging in further.

[AArnott]

Thank you for the report and volunteering to fix. I guess you're probably correct. Certainly an interesting case.