Use Rosyln Language Server for C# parsing and analysis

[timabell]

I'm creating this as a place to gather knowledge that could potentially be put into the documentation or the tool itself if anyone can get it to work.

I attempted to analyse c# files with the CSharperParser built in to gtoolkit, but ran into issue #4298 - this approach seems like it's always going to be a challenge as the c# language specifications continue to evolve rapidly, and maintaining an independent parser of c# like that will be difficult to keep updated.

There was a suggestion to go via xml with https://github.com/srcML/srcML - but I don't fancy that much.

Another possibility might be to connect to the rosyln language server provided by microsoft, as this powers vscode's c# support, and will therefore be kept up to date with new releases of c#. I have not yet figured out how to do this, contributions here most welcome. I will add any useful knowledge I find here. So far I have found:

• The language server protocol spec (from microsoft) https://microsoft.github.io/language-server-protocol/
  • Language server implementation list https://microsoft.github.io/language-server-protocol/implementors/servers/
• Rosyln itself - https://github.com/dotnet/roslyn
• A wrapper library that claims to make it available for other editors - https://github.com/SofusA/roslyn-language-server - this might be a good option
• An omnisharp thing at https://github.com/OmniSharp/omnisharp-roslyn - I'm not quite sure how this fits in to the picture, omnisharp used to be the main way to get editor support for c# but things have changed somewhat - I'm not sure if this thing even works or is up to date now, or how I'd use it.
• Someone trying to use roslyn with the helix editor - https://www.reddit.com/r/HelixEditor/comments/1c5lwc2/using_new_c_roslyn_language_server_with_helix/

[girba]

There exists already support for LSP. We have several connections already (e.g., Rust, Python, CSS). Take a look at subclasses of GtLSPModel from the GToolkit4LSP package.

[timabell]

Unless anyone has already done this, it seems the first step might be to clone GtLSPRustModel into a new class called something like GtLSPCsharpModel and update the downloadExecutable to download from https://github.com/SofusA/roslyn-language-server/releases/latest instead of the rust one.

I've already downloaded that manually and got it running (though I did run into SofusA/roslyn-language-server#97 and have to switch to a newer OS)

That would then allow a Pharo snippet like this

GtLSPCsharpModel downloadExecutable.

• GtLSPRustModel source