How to push LSP Diagnostic using OmniSharp LanguageServer?

Question

I'm using OmniSharp's C# LSP server to implement a simple parsing/language service for a VS Code plugin. I've managed to get the basics up and running, but I've not been able to figure out how to push diagnostic messages to VS Code (like in this typescript sample).

Does anyone have any sample code/hints that would be of use?

Thanks!

Answer 1

Having spoken with @david-driscoll, it turns out I needed to stash a reference to ILanguageServerFacade in my constructor and use the PublishDiagnostics extension method on TextDocument. Ie:

public class TextDocumentSyncHandler : ITextDocumentSyncHandler
{
   private readonly ILanguageServerFacade _facade;

   public TextDocumentSyncHandler(ILanguageServerFacade facade)
   {
      _facade = facade;
   }

   public Task<Unit> Handle(DidChangeTextDocumentParams request, CancellationToken cancellationToken) 
   {
      // Parse your stuff here

      // Diagnostics are sent a document at a time, this example is for demonstration purposes only
      var diagnostics = ImmutableArray<Diagnostic>.Empty.ToBuilder();

      diagnostics.Add(new Diagnostic()
      {
         Code = "ErrorCode_001",
         Severity = DiagnosticSeverity.Error,
         Message = "Something bad happened",
         Range = new Range(0, 0, 0, 0),
         Source = "XXX",
         Tags = new Container<DiagnosticTag>(new DiagnosticTag[] { DiagnosticTag.Unnecessary })
      });

      _facade.TextDocument.PublishDiagnostics(new PublishDiagnosticsParams() 
      {
         Diagnostics = new Container<Diagnostic>(diagnostics.ToArray()),
         Uri = request.TextDocument.Uri,
         Version = request.TextDocument.Version
      });

      return Unit.Task;
   }
}

For real code, you would want a centralised array of Diagnostic objects, but this shows the basics of how to get it done.

Thank you David!