Project.nuget.g.targets should not prepend to MSBuildAllProjects in MSBuild 16 or later

[drewnoakes]

Testing using VS 17 internal preview, but I suspect this goes way back.

For a new .NET 5.0 xUnit project, the following obj\TestProject1.csproj.nuget.g.targets file is generated:

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<Project ToolsVersion="14.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <MSBuildAllProjects>$(MSBuildAllProjects);$(MSBuildThisFileFullPath)</MSBuildAllProjects>
  </PropertyGroup>
  <ImportGroup Condition=" '$(ExcludeRestorePackageImports)' != 'true' ">
    <Import Project="$(NuGetPackageRoot)xunit.core\2.4.1\build\xunit.core.targets" Condition="Exists('$(NuGetPackageRoot)xunit.core\2.4.1\build\xunit.core.targets')" />
    <Import Project="$(NuGetPackageRoot)microsoft.codecoverage\16.7.1\build\netstandard1.0\Microsoft.CodeCoverage.targets" Condition="Exists('$(NuGetPackageRoot)microsoft.codecoverage\16.7.1\build\netstandard1.0\Microsoft.CodeCoverage.targets')" />
    <Import Project="$(NuGetPackageRoot)microsoft.net.test.sdk\16.7.1\build\netcoreapp2.1\Microsoft.NET.Test.Sdk.targets" Condition="Exists('$(NuGetPackageRoot)microsoft.net.test.sdk\16.7.1\build\netcoreapp2.1\Microsoft.NET.Test.Sdk.targets')" />
    <Import Project="$(NuGetPackageRoot)coverlet.collector\1.3.0\build\netstandard1.0\coverlet.collector.targets" Condition="Exists('$(NuGetPackageRoot)coverlet.collector\1.3.0\build\netstandard1.0\coverlet.collector.targets')" />
  </ImportGroup>
</Project>

The MSBuildAllProjectsproperty does not need to be updated with MSBuildThisFileFullPath. There have been several changes over the last few years to stop adding projects to this, as the property can become very large which has an impact on runtime performance.

For more information, see:

• http://www.panopticoncentral.net/2019/07/12/msbuildallprojects-considered-harmful/
• Don't set MSBuildAllProjects for MSBuild 16.0+ dotnet/sdk#2853

To make this work with MSBuild versions earlier than 16, the following could be generated instead:

-    <MSBuildAllProjects>$(MSBuildAllProjects);$(MSBuildThisFileFullPath)</MSBuildAllProjects>
+    <MSBuildAllProjects Condition=" '$(MSBuildVersion)' == '' Or '$(MSBuildVersion)' &lt; '16.0' ">
+      $(MSBuildAllProjects);$(MSBuildThisFileFullPath)
+    </MSBuildAllProjects>

[drewnoakes]

Looks like it's coming from this code:

https://github.com/NuGet/NuGet.Client/blob/5c0589b7137106a7815299952d336bf5fd4a7e95/src/NuGet.Core/NuGet.Commands/RestoreCommand/Utility/BuildAssetsUtils.cs#L191-L195

Also, there are many usages of this property throughout the NuGet org's code, which could be removed.

https://github.com/search?q=org%3ANuGet+MSBuildAllProjects&type=Code