2.78 has "support for .NET 9", so should language features work?

[Marv51]

I updated to docfx 2.78.1 today. We also updated our projects to use the new C# 13 partial properties.
Docfx does not compile this successfully and requires a <LangVersion>preview</LangVersion> in the .csproj project.

Is this a bug, or is this the expected behavior?

I can provide more details as needed, but this seems like a pretty general topic?

Example for partial property:

[GeneratedRegex("abc|def")]
private static partial Regex AbcOrDefProperty { get; };

Example error message:

error CS8703: The modifier 'partial' is not valid for this item in C# 12.0. Please use language version 'preview' or greater.

[KalleOlaviNiemitalo]

C# 13 support would require upgrading the Microsoft.CodeAnalysis.* packages here:

docfx/Directory.Packages.props

Lines 29 to 38 in 618e71b

	<ItemGroup>
	<PackageVersion Include="Microsoft.CodeAnalysis" Version="4.11.0" />
	<PackageVersion Include="Microsoft.CodeAnalysis.Common" Version="4.11.0" />
	<PackageVersion Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.11.0" />
	<PackageVersion Include="Microsoft.CodeAnalysis.CSharp" Version="4.11.0" />
	<PackageVersion Include="Microsoft.CodeAnalysis.VisualBasic.Workspaces" Version="4.11.0" />
	<PackageVersion Include="Microsoft.CodeAnalysis.VisualBasic" Version="4.11.0" />
	<PackageVersion Include="Microsoft.CodeAnalysis.Workspaces.Common" Version="4.11.0" />
	<PackageVersion Include="Microsoft.CodeAnalysis.Workspaces.MSBuild" Version="4.11.0" />
	</ItemGroup>

Version 4.11.0 currently referenced there does not include dotnet/roslyn#74215, which moved the C# 13 features from LanguageVersion.Preview to LanguageVersion.CSharp13 in src/Compilers/CSharp/Portable/Errors/MessageID.cs.

Currently, the latest version of Microsoft.CodeAnalysis is 4.12.0-3.final, which is a prerelease version number; no 4.12.0 version has been released. I guess that prevents dependabot from upgrading the packages automatically.

[Marv51]

Thanks! That actually makes a lot of sense.

[KalleOlaviNiemitalo]

These Roslyn packages were upgraded from 4.11.0 to 4.12.0 in #10448. That change came too late for the DocFX 2.78.2 release but it should be in the next one.