tower-lsp-server

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 hyper for HTTP and tonic for gRPC.

tower-lsp-server 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 stdio or TCP.

Example

use tower_lsp_server::jsonrpc::Result;
use tower_lsp_server::lsp_types::*;
use tower_lsp_server::{Client, LanguageServer, LspService, Server};

#[derive(Debug)]
struct Backend {
    client: Client,
}

#[tower_lsp_server::async_trait]
impl LanguageServer for Backend {
    async fn initialize(&self, _: InitializeParams) -> Result<InitializeResult> {
        Ok(InitializeResult::default())
    }

    async fn initialized(&self, _: InitializedParams) {
        self.client
            .log_message(MessageType::INFO, "server initialized!")
            .await;
    }

    async fn shutdown(&self) -> Result<()> {
        Ok(())
    }
}

#[tokio::main]
async fn main() {
    let stdin = tokio::io::stdin();
    let stdout = tokio::io::stdout();

    let (service, socket) = LspService::new(|client| Backend { client });
    Server::new(stdin, stdout, socket).serve(service).await;
}

Using runtimes other than tokio

By default, tower-lsp-server is configured for use with tokio.

Using tower-lsp-server with other runtimes requires disabling default-features and enabling the runtime-agnostic feature:

[dependencies.tower-lsp-server]
version = "*"
default-features = false
features = ["runtime-agnostic"]

Using proposed features

You can use enable proposed features in the LSP Specification version 3.18 by enabling the proposed Cargo crate feature. Note that there are no semver guarantees to the proposed features so there may be breaking changes between any type of version in the proposed features.

Projects using tower-lsp-server

• Harper
• Deno
• Polarity: both for their language server and their interactive web demo.
• Turborepo

Ecosystem

• tower-lsp-boilerplate - Useful GitHub project template which makes writing new language servers easier.

License

tower-lsp-server is free and open source software distributed under the terms of either the MIT or the Apache 2.0 license, at your option.

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.