rmcp 2.2.0

Rust SDK for Model Context Protocol
Documentation 
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//! SEP-2164: the resource-not-found error code follows the negotiated protocol version.
//!
//! `2026-07-28` and newer get the standard `INVALID_PARAMS` (-32602); older versions
//! keep the legacy `RESOURCE_NOT_FOUND` (-32002).
#![cfg(not(feature = "local"))]
#![cfg(feature = "client")]

use rmcp::{
    ClientHandler, RoleServer, ServerHandler, ServiceError, ServiceExt,
    model::{
        ClientInfo, ErrorCode, ErrorData, ProtocolVersion, ReadResourceRequestParams,
        ReadResourceResult,
    },
    service::RequestContext,
};

#[derive(Debug, Clone, Default)]
struct ResourceServer;

impl ServerHandler for ResourceServer {
    async fn read_resource(
        &self,
        _request: ReadResourceRequestParams,
        _context: RequestContext<RoleServer>,
    ) -> Result<ReadResourceResult, ErrorData> {
        Err(ErrorData::resource_not_found("resource not found", None))
    }
}

#[derive(Debug, Clone)]
struct VersionedClient {
    protocol_version: ProtocolVersion,
}

impl ClientHandler for VersionedClient {
    fn get_info(&self) -> ClientInfo {
        let mut info = ClientInfo::default();
        info.protocol_version = self.protocol_version.clone();
        info
    }
}

async fn not_found_code(client_version: ProtocolVersion) -> ErrorCode {
    let (server_transport, client_transport) = tokio::io::duplex(4096);

    let server_handle = tokio::spawn(async move {
        ResourceServer
            .serve(server_transport)
            .await?
            .waiting()
            .await?;
        anyhow::Ok(())
    });

    let client = VersionedClient {
        protocol_version: client_version,
    }
    .serve(client_transport)
    .await
    .expect("client should connect");

    let error = client
        .read_resource(ReadResourceRequestParams::new("missing://resource"))
        .await
        .expect_err("missing resource should error");

    let code = match error {
        ServiceError::McpError(data) => data.code,
        other => panic!("expected McpError, got: {other:?}"),
    };

    client.cancel().await.expect("client should cancel");
    server_handle.await.expect("server task").expect("server");
    code
}

#[tokio::test]
async fn legacy_version_gets_resource_not_found_code() {
    assert_eq!(
        not_found_code(ProtocolVersion::V_2025_11_25).await,
        ErrorCode::RESOURCE_NOT_FOUND,
    );
}

#[tokio::test]
async fn sep_2164_version_gets_invalid_params_code() {
    assert_eq!(
        not_found_code(ProtocolVersion::V_2026_07_28).await,
        ErrorCode::INVALID_PARAMS,
    );
}