[Feature] Support Roslyn LSP

[Vlaaaaaaad]

Hi,

I'd love to see Zed's C# extension using the Roslyn LSP instead of the OmniSharp Roslyn LSP. Using the Roslyn LSP is now the default and brings several advantages over the OmniSharp Roslyn LSP.

When the C# extension was initially being built, there was a debate on what LSP should be used: OmniSharp Roslyn LSP or the Roslyn LSP? Since the extension was already implemented using OmniSharp Roslyn LSP, the decision was to merge it like that, and then have Roslyn LSP added as a quick follow-up. I was unable to find a PR or an issue tracking that so I thought I should create one 🙂

[Digni]

I just created this PR:
#11

This would add the option to use the roslyn lsp with the help of a wrapper (https://github.com/SofusA/csharp-language-server)
I would love to run the lsp directly but I am not sure on how to do that with the current extension api.

[SofusA]

I can add, that the new language server is a great improvement over omnisharp. It allowed me to go all-in on helix instead of visual studio.

Let me know if you have feature requests for the wrapper, to make it better for integrating with Zed.

[Digni]

@SofusA Have you managed to get the workspace configuration functional?
I am really not sure what the roslyn lsp expects (like the data structure). For Example:

"settings": {
        "csharp|inlay_hints": {
          "csharp_enable_inlay_hints_for_implicit_object_creation": true,
          "csharp_enable_inlay_hints_for_implicit_variable_types": true,
          "csharp_enable_inlay_hints_for_lambda_parameter_types": true
        }
}

or is it flat (like in vscode):

csharp|inlay_hints.csharp_enable_inlay_hints_for_implicit_object_creation: true

[SofusA]

@SofusA Have you managed to get the workspace configuration functional? I am really not sure what the roslyn lsp expects (like the data structure). For Example:

"settings": {
"csharp|inlay_hints": {
"csharp_enable_inlay_hints_for_implicit_object_creation": true,
"csharp_enable_inlay_hints_for_implicit_variable_types": true,
"csharp_enable_inlay_hints_for_lambda_parameter_types": true
}
}
or is it flat (like in vscode):

csharp|inlay_hints.csharp_enable_inlay_hints_for_implicit_object_creation: true

I haven’t tried. I have only used the defaults.
I think the best source for documentation would be the vscode extension. This is where I found information for opening projects and solutions.

[Digni]

I did check and vscode does it differently and then transforms it.
So they have:

"csharp.inlayHints.enableInlayHintsForImplicitObjectCreation": true

which needs to be transformed to:

csharp|inlay_hints.csharp_enable_inlay_hints_for_implicit_object_creation: true

[HalvorNygaard]

Looked into https://github.com/JaneySprings/DotRush? Looks like he is putting in a lot of work around opensource dotnet features in these types of text editors. Looks like it also use the Roslyn LSP under the hood too. Maybe it would make sense to use/integrate/build on it here?

[Digni]

Thanks for pointing that out. I did know of DotRush, but only as the VSCode Extension (Which works great).
But that there is a Zed Extension, I did not know.

It seems he is doing that in a similar way by providing an executable that contains the lsp. (Which in this case seems more than a wrapper).

Instead of scanning the folder for projects/solutions the user needs to provide the solution/projects in the settings.json file (which would solve the issue of several solutions in the project, but ofc you need to configure it for every project)

A big advantage down the line could be, that he also provides the debuggers :VsDbg and NcDbg. The NcDbg one (this is the one from samsung) he even provides compiled versions for the different architectures (as the samsung ones are for example missing osx-arm).

So we could just add it as an additional language server option (as dotrush), as it is more than just a roslyn wrapper.

[SofusA]

My wrappers purpose is only to expose Microsoft.CodeAnalysis.LanguageServer as a language server, that can run outside of vscode.
DotRush seems to do more.

There might be a licence issue with running the dotnet debugger outside of vscode, if I remember correctly

[Digni]

That is true, but that should only applies to VsDbg. The samsung one netcoredbg, can be run.
(https://github.com/Samsung/netcoredbg)

[JaneySprings]

@Digni

user needs to provide the solution/projects in the settings.json file (which would solve the issue of several solutions in the project, but ofc you need to configure it for every project)

This is not necessary if you have a single solution or project.

https://github.com/JaneySprings/DotRush/blob/86fadbba963d16905d4097a23fa0bcb3e501db67/src/DotRush.Roslyn.Server/Services/WorkspaceService.cs#L83-L98