CSharpier_FrameworkVersion is unreliable

[Tyrrrz]

I don't have .NET 7.0 SDK installed anymore, since I've moved my projects off to .NET 8.0. CSharpier_FrameworkVersion sometimes incorrectly resolves to .NET 7.0 due to unreliable heuristics:

csharpier/Src/CSharpier.MsBuild/build/CSharpier.MsBuild.targets

Lines 3 to 4 in ef79538

	<CSharpier_FrameworkVersion Condition="'$(CSharpier_FrameworkVersion)' == ''">$(TargetFramework)</CSharpier_FrameworkVersion>
	<CSharpier_FrameworkVersion Condition="'$(CSharpier_FrameworkVersion)' != 'net6.0' and '$(CSharpier_FrameworkVersion)' != 'net7.0' and '$(CSharpier_FrameworkVersion)' != 'net8.0'">net7.0</CSharpier_FrameworkVersion>

The two most common scenarios are:

• The project is a library that targets .NET Standard 2.1, but .NET 8.0 SDK is used to build it.
• The project is targeting a superset of .NET 8.0, for example net8.0-windows.

In either of these cases, CSharpier resolves to the .NET 7.0 version of the tool, which may not be able to execute (as in my case).

My suggestion is to not rely on the TargetFramework property for this, but instead use the current SDK version, which can be extracted from the NETCoreSdkVersion property, as defined by one of the built-in imports.

[domn1995]

I believe I'm running into this issue in my source generator project. Here's the build output if it helps:
https://github.com/domn1995/dunet/actions/runs/6900832597/job/18802795139?pr=187

[belav]

I believe I'm running into this issue in my source generator project. Here's the build output if it helps: https://github.com/domn1995/dunet/actions/runs/6900832597/job/18802795139?pr=187

That sounds like a problem with the nuget package not being restored correctly, I don't think I've seen that. I know one of the net8 RC's had some issues around restoring tools, but it looks like you are on the official release.