# tower-lsp

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[build-url]: https://github.com/ebkalderon/tower-lsp/actions
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[docs-url]: https://docs.rs/tower-lsp

[Language Server Protocol] implementation for Rust based on [Tower].

[language server protocol]: https://microsoft.github.io/language-server-protocol
[tower]: https://github.com/tower-rs/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.

[`service`]: https://docs.rs/tower-service/
[`hyper`]: https://docs.rs/hyper/
[`tonic`]: https://docs.rs/tonic/

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 `stdio` or TCP.

## Example

```rust
use tower_lsp::jsonrpc::Result;
use tower_lsp::lsp_types::*;
use tower_lsp::{Client, LanguageServer, LspService, Server};

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

#[tower_lsp::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` is configured for use with `tokio`.

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

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

## Using proposed features

You can use enable proposed features in the
[LSP Specification version 3.18](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/)
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.

## Ecosystem

- [tower-lsp-boilerplate](https://github.com/IWANABETHATGUY/tower-lsp-boilerplate) - Useful GitHub project template which makes writing new language servers easier.

## License

`tower-lsp` is free and open source software distributed under the terms of
either the [MIT](LICENSE-MIT) or the [Apache 2.0](LICENSE-APACHE) 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.
