get rid of async-trait

Author: 4t145

crates/mcp-client/Cargo.toml

@@ -14,7 +14,6 @@ eventsource-client = "0.12.0"
 futures = "0.3"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-async-trait = "0.1.83"
 url = "2.5.4"
 thiserror = "1.0"
 anyhow = "1.0"

crates/mcp-client/src/client.rs

@@ -5,7 +5,7 @@ use mcp_core::protocol::{
 };
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
-use std::sync::atomic::{AtomicU64, Ordering};
+use std::{future::Future, sync::atomic::{AtomicU64, Ordering}};
 use thiserror::Error;
 use tokio::sync::Mutex;
 use tower::{Service, ServiceExt}; // for Service::ready()
@@ -75,28 +75,27 @@ pub struct InitializeParams {
     pub client_info: ClientInfo,
 }
 
-#[async_trait::async_trait]
 pub trait McpClientTrait: Send + Sync {
-    async fn initialize(
+    fn initialize(
         &mut self,
         info: ClientInfo,
         capabilities: ClientCapabilities,
-    ) -> Result<InitializeResult, Error>;
+    ) -> impl Future<Output = Result<InitializeResult, Error>> + Send;
 
-    async fn list_resources(
+    fn list_resources(
         &self,
         next_cursor: Option<String>,
-    ) -> Result<ListResourcesResult, Error>;
+    ) -> impl Future<Output = Result<ListResourcesResult, Error>> + Send;
 
-    async fn read_resource(&self, uri: &str) -> Result<ReadResourceResult, Error>;
+    fn read_resource(&self, uri: &str) -> impl Future<Output = Result<ReadResourceResult, Error>> + Send;
 
-    async fn list_tools(&self, next_cursor: Option<String>) -> Result<ListToolsResult, Error>;
+    fn list_tools(&self, next_cursor: Option<String>) -> impl Future<Output = Result<ListToolsResult, Error>> + Send;
 
-    async fn call_tool(&self, name: &str, arguments: Value) -> Result<CallToolResult, Error>;
+    fn call_tool(&self, name: &str, arguments: Value) -> impl Future<Output = Result<CallToolResult, Error>> + Send;
 
-    async fn list_prompts(&self, next_cursor: Option<String>) -> Result<ListPromptsResult, Error>;
+    fn list_prompts(&self, next_cursor: Option<String>) -> impl Future<Output = Result<ListPromptsResult, Error>> + Send;
 
-    async fn get_prompt(&self, name: &str, arguments: Value) -> Result<GetPromptResult, Error>;
+    fn get_prompt(&self, name: &str, arguments: Value) -> impl Future<Output = Result<GetPromptResult, Error>> + Send;
 }
 
 /// The MCP client is the interface for MCP operations.
@@ -232,7 +231,6 @@ where
     }
 }
 
-#[async_trait::async_trait]
 impl<S> McpClientTrait for McpClient<S>
 where
     S: Service<JsonRpcMessage, Response = JsonRpcMessage> + Clone + Send + Sync + 'static,

crates/mcp-client/src/transport/mod.rs

@@ -1,8 +1,7 @@
-use async_trait::async_trait;
 use mcp_core::protocol::JsonRpcMessage;
-use std::collections::HashMap;
+use std::{collections::HashMap, future::Future};
 use thiserror::Error;
-use tokio::sync::{mpsc, oneshot, RwLock};
+use tokio::sync::{RwLock, mpsc, oneshot};
 
 pub type BoxError = Box<dyn std::error::Error + Sync + Send>;
 /// A generic error type for transport operations.
@@ -43,21 +42,22 @@ pub struct TransportMessage {
 }
 
 /// A generic asynchronous transport trait with channel-based communication
-#[async_trait]
 pub trait Transport {
     type Handle: TransportHandle;
 
     /// Start the transport and establish the underlying connection.
     /// Returns the transport handle for sending messages.
-    async fn start(&self) -> Result<Self::Handle, Error>;
+    fn start(&self) -> impl Future<Output = Result<Self::Handle, Error>> + Send;
 
     /// Close the transport and free any resources.
-    async fn close(&self) -> Result<(), Error>;
+    fn close(&self) -> impl Future<Output = Result<(), Error>> + Send;
 }
 
-#[async_trait]
 pub trait TransportHandle: Send + Sync + Clone + 'static {
-    async fn send(&self, message: JsonRpcMessage) -> Result<JsonRpcMessage, Error>;
+    fn send(
+        &self,
+        message: JsonRpcMessage,
+    ) -> impl Future<Output = Result<JsonRpcMessage, Error>> + Send;
 }
 
 // Helper function that contains the common send implementation

crates/mcp-client/src/transport/sse.rs

@@ -1,5 +1,4 @@
 use crate::transport::{Error, PendingRequests, TransportMessage};
-use async_trait::async_trait;
 use eventsource_client::{Client, SSE};
 use futures::TryStreamExt;
 use mcp_core::protocol::{JsonRpcMessage, JsonRpcRequest};
@@ -220,7 +219,6 @@ pub struct SseTransportHandle {
     sender: mpsc::Sender<TransportMessage>,
 }
 
-#[async_trait::async_trait]
 impl TransportHandle for SseTransportHandle {
     async fn send(&self, message: JsonRpcMessage) -> Result<JsonRpcMessage, Error> {
         send_message(&self.sender, message).await
@@ -262,7 +260,6 @@ impl SseTransport {
     }
 }
 
-#[async_trait]
 impl Transport for SseTransport {
     type Handle = SseTransportHandle;
 

crates/mcp-client/src/transport/stdio.rs

@@ -2,7 +2,6 @@ use std::collections::HashMap;
 use std::sync::Arc;
 use tokio::process::{Child, ChildStderr, ChildStdin, ChildStdout, Command};
 
-use async_trait::async_trait;
 use mcp_core::protocol::JsonRpcMessage;
 use tokio::io::{AsyncBufReadExt, AsyncReadExt, AsyncWriteExt, BufReader};
 use tokio::sync::{mpsc, Mutex};
@@ -161,7 +160,6 @@ pub struct StdioTransportHandle {
     error_receiver: Arc<Mutex<mpsc::Receiver<Error>>>,
 }
 
-#[async_trait::async_trait]
 impl TransportHandle for StdioTransportHandle {
     async fn send(&self, message: JsonRpcMessage) -> Result<JsonRpcMessage, Error> {
         let result = send_message(&self.sender, message).await;
@@ -244,7 +242,6 @@ impl StdioTransport {
     }
 }
 
-#[async_trait]
 impl Transport for StdioTransport {
     type Handle = StdioTransportHandle;
 

crates/mcp-core/Cargo.toml

@@ -8,7 +8,6 @@ description = "Core types for Model Context Protocol"
 
 
 [dependencies]
-async-trait = "0.1"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 thiserror = "1.0"

crates/mcp-core/src/handler.rs

@@ -1,4 +1,5 @@
-use async_trait::async_trait;
+use std::future::Future;
+
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
@@ -38,7 +39,6 @@ pub enum PromptError {
 }
 
 /// Trait for implementing MCP tools
-#[async_trait]
 pub trait ToolHandler: Send + Sync + 'static {
     /// The name of the tool
     fn name(&self) -> &'static str;
@@ -50,11 +50,10 @@ pub trait ToolHandler: Send + Sync + 'static {
     fn schema(&self) -> Value;
 
     /// Execute the tool with the given parameters
-    async fn call(&self, params: Value) -> ToolResult<Value>;
+    fn call(&self, params: Value) -> impl Future<Output = ToolResult<Value>> + Send;
 }
 
 /// Trait for implementing MCP resources
-#[async_trait]
 pub trait ResourceTemplateHandler: Send + Sync + 'static {
     /// The URL template for this resource
     fn template() -> &'static str;
@@ -63,7 +62,7 @@ pub trait ResourceTemplateHandler: Send + Sync + 'static {
     fn schema() -> Value;
 
     /// Get the resource value
-    async fn get(&self, params: Value) -> ToolResult<String>;
+    fn get(&self, params: Value) -> impl Future<Output = ToolResult<String>>;
 }
 
 /// Helper function to generate JSON schema for a type

crates/mcp-macros/Cargo.toml

@@ -13,12 +13,10 @@ proc-macro2 = "1.0"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 mcp-core = { path = "../mcp-core" }
-async-trait = "0.1"
 schemars = "0.8"
 convert_case = "0.6.0"
 
 [dev-dependencies]
 tokio = { version = "1.0", features = ["full"] }
-async-trait = "0.1"
 serde_json = "1.0"
 schemars = "0.8"

crates/mcp-server/Cargo.toml

@@ -22,4 +22,3 @@ pin-project = "1.1"
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 tracing-appender = "0.2"
-async-trait = "0.1"

examples/macros/Cargo.toml

@@ -10,7 +10,6 @@ mcp-macros = { path = "../../crates/mcp-macros" }
 tokio = { version = "1", features = ["full"] }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-async-trait = "0.1"
 schemars = "0.8"
 
 [[example]]