Migrate to LSP about cargo-wgsl HOT 6 OPEN

// this is shared data for handlers e.g. config. It must be thread safe
pub struct MyLanguageServer { client: Client /* other fields can go here */ }

#[tower_lsp::async_trait]
impl LanguageServer for MyLanguageServer {
    // `InitializeParams` includes client-side configs among other things.
    // The crate passes immutable refs, so working with `self` is inconvenient, because it requires
    // thread-safe (`Sync`) interior mutability. Both `tokio` and the `once_cell` crate have a `OnceCell`
    // which I find make it easier. I prefer the latter because of its cleaner interface.
    async fn initialize(&self, params: InitializeParams) -> Result<InitializeResult> {
        Ok(InitializeResult::default())
    }

    // called upon requesting graceful shut down. This is different from process exit.
    async fn shutdown(&self) -> Result<()> { Ok(()) }

    // LSP events are modeled as functions on this trait, which makes implementing them straightforward,
    // but all references are immutable so they have have the same inconveniences as `initialize` 
    async fn did_open(&self, params: DidOpenTextDocumentParams) {}
}

let rt = tokio::runtime::Runtime::new().unwrap();
rt.block_on(async {
    let stdin = tokio::io::stdin();
    let stdout = tokio::io::stdout();
    let (service, socket) = LspService::new(MyLanguageServer::new); // MyLanguageServer::new(Client) -> Self
    Server::new(stdin, stdout, socket).serve(service).await;
})