Make LanguageServer::initialize() asynchronous

README.md

@@ -48,7 +48,7 @@ struct Backend;
 
 #[tower_lsp::async_trait]
 impl LanguageServer for Backend {
-    fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
+    async fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
         Ok(InitializeResult::default())
     }
 

examples/custom_notification.rs

@@ -33,7 +33,7 @@ struct Backend;
 
 #[tower_lsp::async_trait]
 impl LanguageServer for Backend {
-    fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
+    async fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
         Ok(InitializeResult {
             server_info: None,
             capabilities: ServerCapabilities {

examples/server.rs

@@ -8,7 +8,7 @@ struct Backend;
 
 #[tower_lsp::async_trait]
 impl LanguageServer for Backend {
-    fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
+    async fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
         Ok(InitializeResult {
             server_info: None,
             capabilities: ServerCapabilities {

src/delegate.rs

@@ -13,7 +13,7 @@ use futures::compat::Compat;
 use futures::future::{self, FutureExt, TryFutureExt};
 use futures::Stream;
 use jsonrpc_core::types::{ErrorCode, Output, Params};
-use jsonrpc_core::{Error, Result as RpcResult};
+use jsonrpc_core::Error;
 use jsonrpc_derive::rpc;
 use log::{error, info};
 use lsp_types::notification::{Notification, *};
@@ -51,7 +51,7 @@ pub trait LanguageServerCore {
     // Initialization
 
     #[rpc(name = "initialize", raw_params)]
-    fn initialize(&self, params: Params) -> RpcResult<InitializeResult>;
+    fn initialize(&self, params: Params) -> BoxFuture<InitializeResult>;
 
     #[rpc(name = "initialized", raw_params)]
     fn initialized(&self, params: Params);
@@ -247,15 +247,22 @@ macro_rules! delegate_request {
 }
 
 impl<T: LanguageServer> LanguageServerCore for Delegate<T> {
-    fn initialize(&self, params: Params) -> RpcResult<InitializeResult> {
+    fn initialize(&self, params: Params) -> BoxFuture<InitializeResult> {
         if !self.initialized.load(Ordering::SeqCst) {
-            let params: InitializeParams = params.parse()?;
-            let response = self.server.initialize(&self.client, params)?;
-            info!("language server initialized");
-            self.initialized.store(true, Ordering::SeqCst);
-            Ok(response)
+            let server = self.server.clone();
+            let initialized = self.initialized.clone();
+            let client = self.client.clone();
+            let fut = async move {
+                let params = params.parse()?;
+                let response = server.initialize(&client, params).await?;
+                info!("language server initialized");
+                initialized.store(true, Ordering::SeqCst);
+                Ok(response)
+            };
+
+            fut.boxed().compat()
         } else {
-            Err(Error::invalid_request())
+            future::err(Error::invalid_request()).boxed().compat()
         }
     }
 

src/lib.rs

@@ -14,7 +14,7 @@
 //!
 //! #[tower_lsp::async_trait]
 //! impl LanguageServer for Backend {
-//!     fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
+//!     async fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
 //!         Ok(InitializeResult::default())
 //!     }
 //!
@@ -100,7 +100,11 @@ pub trait LanguageServer: Send + Sync + 'static {
     ///
     /// This method is guaranteed to only execute once. If the client sends this request to the
     /// server again, the server will respond with JSON-RPC error code `-32600` (invalid request).
-    fn initialize(&self, client: &Client, params: InitializeParams) -> Result<InitializeResult>;
+    async fn initialize(
+        &self,
+        client: &Client,
+        params: InitializeParams,
+    ) -> Result<InitializeResult>;
 
     /// The [`initialized`] notification is sent from the client to the server after the client
     /// received the result of the initialize request but before the client sends anything else.
@@ -735,8 +739,12 @@ pub trait LanguageServer: Send + Sync + 'static {
 
 #[async_trait]
 impl<S: ?Sized + LanguageServer> LanguageServer for Box<S> {
-    fn initialize(&self, client: &Client, params: InitializeParams) -> Result<InitializeResult> {
-        (**self).initialize(client, params)
+    async fn initialize(
+        &self,
+        client: &Client,
+        params: InitializeParams,
+    ) -> Result<InitializeResult> {
+        (**self).initialize(client, params).await
     }
 
     async fn initialized(&self, client: &Client, params: InitializedParams) {

src/service.rs

@@ -143,7 +143,7 @@ mod tests {
 
     #[async_trait]
     impl LanguageServer for Mock {
-        fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
+        async fn initialize(&self, _: &Client, _: InitializeParams) -> Result<InitializeResult> {
             Ok(InitializeResult::default())
         }