LSP Server not working in Visual Studio

[gep13]

I have been setting up an LSP implementation for Chocolatey nuspec files in VSCode, and this has been working well. I am now trying to take the same Language Server implementation and run it in Visual Studio. When I try this, I get the following error returned:

The code that I am using the initialise the client within Visual Studio is the following:

    [ContentType("nuspec")]
    [Export(typeof(ILanguageClient))]
    public class ChocolateyLanguageClient : ILanguageClient
    {
        public string Name => "Chocolatey Language Server Client";

        public IEnumerable<string> ConfigurationSections => null;

        public object InitializationOptions => null;

        public IEnumerable<string> FilesToWatch => null;

        public event AsyncEventHandler<EventArgs> StartAsync;
        public event AsyncEventHandler<EventArgs> StopAsync;

        public async Task<Connection> ActivateAsync(CancellationToken token)
        {
            await Task.Yield();

            var info = new ProcessStartInfo();
            info.FileName = "dotnet";
            info.Arguments = "C:\\github_local\\gep13\\chocolatey-vs\\lib\\ChocolateyLanguageServer\\Chocolatey.Language.Server.dll";
            info.RedirectStandardInput = true;
            info.RedirectStandardOutput = true;
            info.UseShellExecute = false;
            info.CreateNoWindow = true;

            Process process = new Process();
            process.StartInfo = info;

            if (process.Start())
            {
                return new Connection(process.StandardOutput.BaseStream, process.StandardInput.BaseStream);
            }

            return null;
        }

        public async Task OnLoadedAsync()
        {
            await StartAsync?.InvokeAsync(this, EventArgs.Empty);
        }

        public Task OnServerInitializedAsync()
        {
            return Task.CompletedTask;
        }

        public Task OnServerInitializeFailedAsync(Exception e)
        {
            return Task.CompletedTask;
        }
    }

Is there additional configuration that needs to be provided, or is this a bug that needs to be addressed. Let me know if you need any further information.

[gep13]

@mholo65 @david-driscoll @tintoy any ideas about the above?

[gep13]

Seems the related code is here:

csharp-language-server-protocol/src/Server/ClientCapabilityProvider.cs

Lines 28 to 30 in 9fa60ff

	var handlerType = typeof(T).GetTypeInfo().ImplementedInterfaces
	.Single(x => x.GetTypeInfo().IsGenericType && x.GetTypeInfo().GetGenericTypeDefinition() == typeof(ConnectedCapability<>))
	.GetTypeInfo().GetGenericArguments()[0].GetTypeInfo();

I am using the 0.12.0 version of OmniSharp.Extensions.LanguageServer.

[gep13]

I had a concern that the issue was the custom implementation of the ConfigurationHandler that I was using, but I have just removed that, and I am still getting the same error.

[NickAcPT]

I've had some problems like that when I tried to run my language server on Sublime (with the LSP plugin) and on IntelliJ. Sadly, I no longer have the logs.
Don't quote me on this, but I think it might be something related to static registration since the error doesn't happen for me on vscode.

[bjorkstromm]

IIRC, I was able to reproduce using the Client bits in the OmniSharp.Extensions LSP library. I’ll have a look in the upcoming days.

[bjorkstromm]

Did some debugging. It currently fails due to the fact that SynchronizationCapability implements generic interface ConnectedCapability<T> more than once. I am able to reproduce via unit tests by adding typeof(SynchronizationCapability) to ClientCapabilityProviderTests.

Will try to provide a fix in the upcoming days.

[gep13]

@mholo65 nice one!

Any thoughts on why this works in VSCode, but not in Visual Studio?

[bjorkstromm]

@gep13 I'd go with same theory as @NickAcPT regarding static and dynamic registrations.

[gep13]

@mholo65 ah, sorry, missed that part!

[bjorkstromm]

I managed to find a fix for this and submitted a PR #133. Tested it out with OmniSharp, and wasn't able to reproduce the bug anymore. Also tested OmniSharp with VSCode, and everything seemed to work fine.