lspf is an async Rust framework for implementing Language Server Protocol servers and clients. This guide creates the smallest useful stdio server.

Requirements ​

  • Rust 1.98 or newer.
  • Familiarity with async fn and Cargo.

Install ​

Create a binary crate and add lspf with its default stdio transport:

console
cargo new my-language-server
cd my-language-server
cargo add lspf
cargo add tokio --features macros,rt-multi-thread

The default lspf feature set includes stdio. Select transport features explicitly if your application uses TCP, WebSocket, or a worker channel.

Build a server ​

rust
use std::sync::Arc;

use lspf::types::{Hover, HoverContents, HoverParams, MarkedString};
use lspf::{CancellationToken, LspError, Server, ServerContext};

struct State;

async fn hover(
    _state: Arc<State>,
    _ctx: ServerContext,
    _params: HoverParams,
    _cancellation: CancellationToken,
) -> Result<Option<Hover>, LspError> {
    Ok(Some(Hover {
        contents: HoverContents::Scalar(MarkedString::String("Hello from lspf".into())),
        range: None,
    }))
}

#[tokio::main]
async fn main() -> lspf::Result<()> {
    let server = Server::builder(State)
        .feature(lspf::features::hover(), hover)
        .build()?;

    let outcome = lspf::stdio(server).serve().await?;
    std::process::exit(outcome.code());
}

The hover() descriptor fixes the wire method, parameter type, result type, and advertised capability together. There is no separate ServerCapabilities value to keep synchronized.

Next steps ​