Language Server Framework

A modern, high-performance .NET framework for building Language Server Protocol (LSP) servers with full LSP 3.18 specification support.

✨ Features

• 🎯 Full LSP 3.18 Support - Complete implementation of the latest LSP specification
• ⚡ High Performance - Built with System.Text.Json source generation for optimal performance
• 🚀 AOT Ready - Full support for Ahead-of-Time (AOT) compilation
• 📦 Zero Dependencies - No dependency on Newtonsoft.Json or other third-party libraries
• 🪟 Window & Progress - Complete support for window messages, logging, and progress reporting
• 🔧 Easy to Use - Simple, intuitive API for building language servers
• 📊 Performance Metrics - Built-in performance monitoring and telemetry support
• 🎨 Type Safe - Strongly typed protocol messages with full IntelliSense support

📦 Installation

Install via NuGet Package Manager:

dotnet add package EmmyLua.LanguageServer.Framework

Or via Package Manager Console:

Install-Package EmmyLua.LanguageServer.Framework

🚀 Quick Start

Basic Language Server

using EmmyLua.LanguageServer.Framework.Server;
using EmmyLua.LanguageServer.Framework.Protocol.Message.Initialize;

// Create a language server
var server = LanguageServer.From(Console.OpenStandardInput(), Console.OpenStandardOutput());

// Handle initialization
server.OnInitialize((request, serverInfo) =>
{
    serverInfo.Name = "My Language Server";
    serverInfo.Version = "1.0.0";
    return Task.CompletedTask;
});

// Handle initialized notification
server.OnInitialized(async (request) =>
{
    await server.Client.LogInfo("Server initialized!");
});

// Run the server
await server.Run();

Adding Handlers

using EmmyLua.LanguageServer.Framework.Server.Handler;

// Create a hover handler
public class MyHoverHandler : HoverHandlerBase
{
    protected override Task<Hover?> Handle(HoverParams request, CancellationToken token)
    {
        var hover = new Hover
        {
            Contents = new MarkupContent
            {
                Kind = MarkupKind.Markdown,
                Value = "**Hello from LSP!**"
            }
        };
        return Task.FromResult<Hover?>(hover);
    }

    public override void RegisterCapability(ServerCapabilities serverCapabilities,
        ClientCapabilities clientCapabilities)
    {
        serverCapabilities.HoverProvider = true;
    }
}

// Add handler to server
server.AddHandler(new MyHoverHandler());

📚 Documentation

Window Features

Display messages and collect user input:

// Show a message
await server.Client.ShowMessage(new ShowMessageParams
{
    Type = MessageType.Info,
    Message = "Operation completed successfully!"
});

// Request user action
var result = await server.Client.ShowMessageRequest(new ShowMessageRequestParams
{
    Type = MessageType.Warning,
    Message = "Do you want to continue?",
    Actions = new List<MessageActionItem>
    {
        new() { Title = "Yes" },
        new() { Title = "No" }
    }
}, cancellationToken);

// Log messages
await server.Client.LogError("An error occurred");
await server.Client.LogInfo("Processing file...");

Progress Reporting

Report progress for long-running operations:

// Using the helper class (recommended)
using var progress = await WorkDoneProgressReporter.Create(
    server.Client,
    title: "Analyzing workspace",
    cancellable: true
);

for (int i = 0; i < 100; i++)
{
    await progress.Report($"Processing file {i + 1}/100", (uint)i);
}

await progress.End("Analysis complete!");

For detailed examples, see LSP_WINDOW_PROGRESS_USAGE.md

Performance Monitoring

Enable performance metrics to monitor your server:

var options = new LanguageServerOptions
{
    EnablePerformanceTracing = true,
    PerformanceMetricsPrintInterval = TimeSpan.FromMinutes(5)
};

var server = LanguageServer.From(input, output, options);

// Get metrics at any time
var metrics = server.GetMetrics();
Console.WriteLine($"Total requests: {metrics.TotalRequestsHandled}");
Console.WriteLine($"Average duration: {metrics.AverageRequestDurationMs}ms");

🎯 Supported LSP Features

Text Document Synchronization

• ✅DidOpen / DidChange / DidClose / DidSave
• ✅ WillSave / WillSaveWaitUntil

Language Features

• ✅ Completion (with resolve support)
• ✅ Hover
• ✅ Signature Help
• ✅ Definition / Declaration / Type Definition / Implementation
• ✅ References
• ✅ Document Highlight
• ✅ Document Symbol
• ✅ Code Action
• ✅ Code Lens
• ✅ Document Link
• ✅ Document Color / Color Presentation
• ✅ Document Formatting / Range Formatting / On Type Formatting
• ✅ Rename / Prepare Rename
• ✅ Folding Range
• ✅ Selection Range
• ✅ Call Hierarchy
• ✅ Semantic Tokens
• ✅ Inlay Hint
• ✅ Inline Value
• ✅ Type Hierarchy
• ✅ Inline Completion
• ✅ Linked Editing Range

Workspace Features

• ✅ Workspace Symbols
• ✅ Configuration
• ✅ Workspace Folders
• ✅ File Operations (Create/Rename/Delete)
• ✅ File Watching
• ✅ Diagnostics
• ✅ Execute Command
• ✅ Apply Edit

Window Features

• ✅ ShowMessage / ShowMessageRequest
• ✅ LogMessage
• ✅ Work Done Progress
• ✅ Telemetry

🏗️ Architecture

The framework is designed with extensibility and performance in mind:

┌─────────────────────────────────────────┐
│     Language Server Application         │
├─────────────────────────────────────────┤
│           Handler Layer                 │
│  (HoverHandler, CompletionHandler...)   │
├─────────────────────────────────────────┤
│         LanguageServer Core             │
│   (Protocol, Routing, Lifecycle)        │
├─────────────────────────────────────────┤
│      JSON-RPC Protocol Layer            │
│  (JsonProtocolReader/Writer)            │
├─────────────────────────────────────────┤
│         Transport Layer (stdio)         │
└─────────────────────────────────────────┘

📖 Examples

Check out the LanguageServer.Test project for a complete working example that demonstrates:

• Server initialization
• Multiple handlers implementation
• Configuration management
• Progress reporting
• Error handling

🌟 Projects Using This Framework

• EmmyLuaAnalyzer - A feature-rich Lua language server

🤝 Contributing

Contributions are welcome! Please read our Contributing Guide for details on how to submit pull requests, report issues, and contribute to the project.

📝 License

This project is licensed under the MIT License - see the LICENSE file for details.

🔗 Resources

• LSP Specification 3.18
• Language Server Protocol
• NuGet Package

💬 Support

• 📫 Report bugs via GitHub Issues
• 💡 Request features via GitHub Discussions

Made with ❤️ by the EmmyLua community