refactor: Extract shared MCP Stdio NDJSON parsing loop into mcp-stdio library

nvim-core/src/lib.rs

@@ -20,47 +20,7 @@ pub struct JsonRpcResponse {
     pub error: Option<Value>,
 }
 
-pub async fn read_message<R: tokio::io::AsyncRead + Unpin>(
-    stdin: &mut BufReader<R>,
-) -> Option<JsonRpcRequest> {
-    let mut length = 0;
-    loop {
-        let mut line = String::new();
-        if stdin.read_line(&mut line).await.unwrap_or(0) == 0 {
-            return None;
-        }
 
-        if line.starts_with('{') {
-            return match serde_json::from_str::<JsonRpcRequest>(line.trim_end()) {
-                Ok(req) => Some(req),
-                Err(e) => {
-                    tracing::error!(
-                        "Failed to parse JSON-RPC request from JSONL: {}. Payload: {}",
-                        e,
-                        line
-                    );
-                    None
-                }
-            };
-        }
-
-        let line = line.trim_end();
-        if line.is_empty() {
-            break;
-        }
-        let lower_line = line.to_lowercase();
-        if let Some(len_str) = lower_line.strip_prefix("content-length:") {
-            length = len_str.trim().parse().unwrap_or(0);
-        }
-    }
-    if length == 0 {
-        return None;
-    }
-    let mut buffer = vec![0; length];
-    stdin.read_exact(&mut buffer).await.unwrap_or(0);
-
-    serde_json::from_slice(&buffer).ok()
-}
 
 pub async fn send_response(response: JsonRpcResponse) {
     let msg = serde_json::to_string(&response).unwrap();
@@ -508,17 +468,25 @@ pub async fn run_mcp_loop(app_name: &str, app_version: &str) {
     tracing::info!("{} MCP server started", app_name);
     let mut stdin = tokio::io::BufReader::new(tokio::io::stdin());
     loop {
-        let msg = match read_message(&mut stdin).await {
-            Some(m) => {
-                tracing::info!("Received message method: {}", m.method);
-                m
-            }
+        let raw_msg = match mcp_stdio::read_mcp_message(&mut stdin).await {
+            Some(m) => m,
             None => {
                 tracing::info!("Stdin closed, exiting loop");
                 break;
             }
         };
 
+        let msg = match serde_json::from_str::<JsonRpcRequest>(&raw_msg) {
+            Ok(m) => {
+                tracing::info!("Received message method: {}", m.method);
+                m
+            },
+            Err(e) => {
+                tracing::error!("Failed to parse JSON-RPC request from JSONL: {}. Payload: {}", e, raw_msg);
+                continue;
+            }
+        };
+
         let app_name = app_name.to_string();
         let app_version = app_version.to_string();
 
@@ -915,3 +883,4 @@ mod tests {
         assert!(req.is_none());
     }
 }
+