tower-lsp 0.4.1

Language Server Protocol implementation based on Tower


Build Status Documentation

Language Server Protocol implementation for Rust based on Tower.

Tower is a simple and composable framework for implementing asynchronous services in Rust. Central to Tower is the Service trait, which provides the necessary abstractions for defining request/response clients and servers. Examples of protocols implemented using the Service trait include tower-web and tower-grpc.

This library (tower-lsp) provides a simple implementation of the Language Server Protocol (LSP) that makes it easy to write your own language server. It consists of three parts:

  • The LanguageServer trait which defines the behavior of your language server.
  • The asynchronous LspService delegate which wraps your language server implementation and defines the behavior of the protocol.
  • A Server which spawns the LspService and processes requests and responses over stdin and stdout.


use futures::future;
use jsonrpc_core::{BoxFuture, Result};
use serde_json::Value;
use tower_lsp::lsp_types::*;
use tower_lsp::{LanguageServer, LspService, Printer, Server};

#[derive(Debug, Default)]
struct Backend;

impl LanguageServer for Backend {
    type ShutdownFuture = BoxFuture<()>;
    type SymbolFuture = BoxFuture<Option<Vec<SymbolInformation>>>;
    type ExecuteFuture = BoxFuture<Option<Value>>;
    type CompletionFuture = BoxFuture<Option<CompletionResponse>>;
    type HoverFuture = BoxFuture<Option<Hover>>;
    type HighlightFuture = BoxFuture<Option<Vec<DocumentHighlight>>>;

    fn initialize(&self, _: &Printer, _: InitializeParams) -> Result<InitializeResult> {

    fn initialized(&self, printer: &Printer, _: InitializedParams) {
        printer.log_message(MessageType::Info, "server initialized!");

    fn shutdown(&self) -> Self::ShutdownFuture {

    fn symbol(&self, _: WorkspaceSymbolParams) -> Self::SymbolFuture {

    fn execute_command(&self, _: &Printer, _: ExecuteCommandParams) -> Self::ExecuteFuture {

    fn completion(&self, _: CompletionParams) -> Self::CompletionFuture {

    fn hover(&self, _: TextDocumentPositionParams) -> Self::HoverFuture {

    fn document_highlight(&self, _: TextDocumentPositionParams) -> Self::HighlightFuture {

fn main() {
    let stdin = tokio::io::stdin();
    let stdout = tokio::io::stdout();

    let (service, messages) = LspService::new(Backend::default());
    let handle = service.close_handle();
    let server = Server::new(stdin, stdout)



tower-lsp is free and open source software distributed under the terms of both the MIT and the Apache 2.0 licenses.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.