Feedback VS Code Support: Let user choose LangVersion instead of defaulting to "latest"

There isn't a dedicated forum for VSCode editor support, so I am posting here hoping that any Unity staff could see and point it to the right people.

My feedback/feature request is to let the user choose what LangVersion is used in csproj file, so that VSCode C# extension could provide relevant information.

The official C# extension of VSCode is way ahead of Unity in language feature support -- they already moved on to C# 9. Because of this, the latest version of C# LangVersion is now "9.0". However, the generated C# project by Unity specifies LangVersion as "latest" and thus VSCode C# defaults the language to 9.0 and suggesting code fixes in C# 9 that Unity's C# 8 compiler does not yet recognize. For example, pattern matching:

Code (CSharp):

1. // Original code:
2. Notification notification = args.Context as Notification;
3. if (notification == null)
4.     return;
5.  
6. // LangVersion: latest
7. // Code fix with C# 9 feature:
8. if(args.Context is not Notification notification)
9.     return;

However, VSCode C# extension already supports different code fixes based on LangVersion. If I change manually LangVersion to "8.0" in csproj file:

Code (csharp):

1.  <PropertyGroup>
2.     <LangVersion>8.0</LangVersion>
3.   </PropertyGroup>

The code fix becomes:

Code (CSharp):

1. // Older C# code fix:
2. if(!(args.Context is Notification notification))
3.      return;

There could be other use cases for this new feature, say if someone wants to limit themselves to use a specific language version in order to maintain source compatibility with some other older Unity projects, like Asset Stores authors.

 

This is definitely an issue for me also!

 

I'm not sure, but I think Unity partially supports C# 9 features that don't need runtime support, but I can be mistaken and confused with C# 8, which will not be fully supported until 2021.2.

 

Created an issue for this problem at github repo of the VSCode-support package: https://github.com/Unity-Technologies/com.unity.ide.vscode/issues/12