Intermitent build issues of MSBuild repo - xml CDATA escaping not properly interpreted

[JanKrivanek]

Context

Intermittent build errors of our repo indicating that xml was incorrectly parsed and 'CDATA' escaping sequence spilled over into the content

C:\src\msbuild-2\artifacts\obj\Microsoft.Build.BuildCheck.UnitTests\Debug\net472\BuildCheckUnitTestsConstants.cs(1,1): error CS1525: Invalid expression term '<' [C:\src\msbuild-2\src\BuildCheck.UnitTests\Microsoft.Build.BuildCheck.UnitTests.csproj::TargetFramework=net472]
C:\src\msbuild-2\artifacts\obj\Microsoft.Build.BuildCheck.UnitTests\Debug\net472\BuildCheckUnitTestsConstants.cs(1,10): error CS1003: Syntax error, ']' expected [C:\src\msbuild-2\src\BuildCheck.UnitTests\Microsoft.Build.BuildCheck.UnitTests.csproj::TargetFramework=net472]
C:\src\msbuild-2\artifacts\obj\Microsoft.Build.BuildCheck.UnitTests\Debug\net472\BuildCheckUnitTestsConstants.cs(1,10): error CS1002: ; expected [C:\src\msbuild-2\src\BuildCheck.UnitTests\Microsoft.Build.BuildCheck.UnitTests.csproj::TargetFramework=net472]
C:\src\msbuild-2\artifacts\obj\Microsoft.Build.BuildCheck.UnitTests\Debug\net472\BuildCheckUnitTestsConstants.cs(10,7): error CS1022: Type or namespace definition, or end-of-file expected [C:\src\msbuild-2\src\BuildCheck.UnitTests\Microsoft.Build.BuildCheck.UnitTests.csproj::TargetFramework=net472]
C:\src\msbuild-2\artifacts\obj\Microsoft.Build.BuildCheck.UnitTests\Debug\net472\BuildCheckUnitTestsConstants.cs(10,9): error CS8803: Top-level statements must precede namespace and type declarations. [C:\src\msbuild-2\src\BuildCheck.UnitTests\Microsoft.Build.BuildCheck.UnitTests.csproj::TargetFramework=net472]
C:\src\msbuild-2\artifacts\obj\Microsoft.Build.BuildCheck.UnitTests\Debug\net472\BuildCheckUnitTestsConstants.cs(10,9): error CS1525: Invalid expression term '>' [C:\src\msbuild-2\src\BuildCheck.UnitTests\Microsoft.Build.BuildCheck.UnitTests.csproj::TargetFramework=net472]
C:\src\msbuild-2\artifacts\obj\Microsoft.Build.BuildCheck.UnitTests\Debug\net472\BuildCheckUnitTestsConstants.cs(10,10): error CS1733: Expected expression [C:\src\msbuild-2\src\BuildCheck.UnitTests\Microsoft.Build.BuildCheck.UnitTests.csproj::TargetFramework=net472]
C:\src\msbuild-2\artifacts\obj\Microsoft.Build.BuildCheck.UnitTests\Debug\net472\BuildCheckUnitTestsConstants.cs(10,10): error CS1002: ; expected [C:\src\msbuild-2\src\BuildCheck.UnitTests\Microsoft.Build.BuildCheck.UnitTests.csproj::TargetFramework=net472]

Looking on the file it complains about - it realy contains unexpected xml escaping sequences:

BuildCheckUnitTestsConstants.cs:

<![CDATA[
namespace Microsoft.Build.BuildCheck.UnitTests
{
    internal sealed class BuildCheckUnitTestsConstants
    {
        public const string MicrosoftBuildPackageVersion = @"17.14.0-dev-24620-01";
        public const string RepoRoot = @"C:\src\msbuild-2\";
    }
}
      ]]>

It seems like the CDATA from the msbuild file was not properly interpreted:

msbuild/src/BuildCheck.UnitTests/Microsoft.Build.BuildCheck.UnitTests.csproj

Lines 53 to 74 in a71903d

	<Target Name="AddGeneratedFile" BeforeTargets="BeforeCompile;CoreCompile" Inputs="$(MSBuildAllProjects)" Outputs="$(IntermediateOutputPath)BuildCheckUnitTestsConstants.cs">
	<PropertyGroup>
	<GeneratedText>
	<![CDATA[
	namespace Microsoft.Build.BuildCheck.UnitTests
	{
	internal sealed class BuildCheckUnitTestsConstants
	{
	public const string MicrosoftBuildPackageVersion = @"$(Version)"%3B
	public const string RepoRoot = @"$(RepoRoot)"%3B
	}
	}
	]]>
	</GeneratedText>
	<GeneratedFilePath>$(IntermediateOutputPath)BuildCheckUnitTestsConstants.cs</GeneratedFilePath>
	</PropertyGroup>
	<ItemGroup>
	<Compile Include="$(GeneratedFilePath)" />
	<FileWrites Include="$(GeneratedFilePath)" />
	</ItemGroup>
	<WriteLinesToFile Lines="$(GeneratedText)" File="$(GeneratedFilePath)" WriteOnlyWhenDifferent="true" Overwrite="true" />
	</Target>

Repro steps

I'm not sure about specific conditions - but it appears every couple full builds. Then I need to clean the artifacts folder and issue is gone for some time

Binlog

msbuild-cdata-issue.binlog.txt

Note

This seems related to https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1980399/, https://developercommunity.visualstudio.com/t/Project-Generated-Files-Sometimes-Contai/10604117