Language Server Protocol for golang

Language Server Protocol implementation in Go.

Design notes

The package does not include JSON RPC handling as that is better left to other packages.

Example

Example code using github.com/sourcegraph/jsonrpc2

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net"
	"os"

	"github.com/laravel-ls/protocol"
	"github.com/sourcegraph/jsonrpc2"
)

func handleInitialize(params protocol.InitializeParams) (protocol.InitializeResult, error) {
	// Initialization logic
	// Read more at: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#initialize
	return protocol.InitializeResult{
		Capabilities: protocol.ServerCapabilities{
			TextDocumentSync: protocol.TextDocumentSyncKindFull,
		},
		ServerInfo: &protocol.ServerInfo{
			Name:    "My LSP Server",
			Version: "1.0.0",
		},
	}, nil
}

func handler(ctx context.Context, conn *jsonrpc2.Conn, req *jsonrpc2.Request) (any, error) {
	switch req.Method {
	case protocol.MethodInitialize:
		var params protocol.InitializeParams
		if err := json.Unmarshal(*req.Params, &params); err != nil {
			return nil, err
		}
		return handleInitialize(params)
	// ... add more methods
	default:
		// Respond with a method not found error
		return nil, &jsonrpc2.Error{
			Code:    jsonrpc2.CodeMethodNotFound,
			Message: fmt.Sprintf("Method %s not found", req.Method),
		}
	}
}

func handleConn(ctx context.Context, conn io.ReadWriteCloser) error {
	stream := jsonrpc2.NewBufferedStream(conn, jsonrpc2.VSCodeObjectCodec{})
	rpc := jsonrpc2.NewConn(ctx, stream, jsonrpc2.HandlerWithError(handler))

	select {
	case <-ctx.Done():
		return fmt.Errorf("context closed")
	case <-rpc.DisconnectNotify():
		return nil
	}
}

func main() {
	// example TCP server.
	ctx := context.Background()
	logger := log.New(os.Stderr, "[tcp-lsp] ", log.LstdFlags|log.Lmicroseconds)

	addr := "127.0.0.1:4389"
	l, err := net.Listen("tcp", addr)
	if err != nil {
		log.Fatal(err)
	}
	logger.Println("Listening on", addr)

	for {
		conn, err := l.Accept()
		if err != nil {
			logger.Println("accept error:", err)
			continue
		}

		logger.Println("Client connected:", conn.RemoteAddr())

		go func(c net.Conn) {
			defer c.Close()
			handleConn(ctx, c)
		}(conn)
	}
}

You can test your server with the following command on linux:

printf 'Content-Length: 58\r\n\r\n{"jsonrpc":"2.0","id":1,"method":"initialize","params":{}}' | nc 127.0.0.1 4389

Author

Henrik Hautakoski henrik@shufflingpixels.com