[codex][app-server] improve error response for client requests (#6050)

Author: apanasenko-oai

codex-rs/app-server/src/message_processor.rs

@@ -64,64 +64,79 @@ impl MessageProcessor {
 
     pub(crate) async fn process_request(&mut self, request: JSONRPCRequest) {
         let request_id = request.id.clone();
-        if let Ok(request_json) = serde_json::to_value(request)
-            && let Ok(codex_request) = serde_json::from_value::<ClientRequest>(request_json)
-        {
-            match codex_request {
-                // Handle Initialize internally so CodexMessageProcessor does not have to concern
-                // itself with the `initialized` bool.
-                ClientRequest::Initialize { request_id, params } => {
-                    if self.initialized {
-                        let error = JSONRPCErrorError {
-                            code: INVALID_REQUEST_ERROR_CODE,
-                            message: "Already initialized".to_string(),
-                            data: None,
-                        };
-                        self.outgoing.send_error(request_id, error).await;
-                        return;
-                    } else {
-                        let ClientInfo {
-                            name,
-                            title: _title,
-                            version,
-                        } = params.client_info;
-                        let user_agent_suffix = format!("{name}; {version}");
-                        if let Ok(mut suffix) = USER_AGENT_SUFFIX.lock() {
-                            *suffix = Some(user_agent_suffix);
-                        }
+        let request_json = match serde_json::to_value(&request) {
+            Ok(request_json) => request_json,
+            Err(err) => {
+                let error = JSONRPCErrorError {
+                    code: INVALID_REQUEST_ERROR_CODE,
+                    message: format!("Invalid request: {err}"),
+                    data: None,
+                };
+                self.outgoing.send_error(request_id, error).await;
+                return;
+            }
+        };
 
-                        let user_agent = get_codex_user_agent();
-                        let response = InitializeResponse { user_agent };
-                        self.outgoing.send_response(request_id, response).await;
+        let codex_request = match serde_json::from_value::<ClientRequest>(request_json) {
+            Ok(codex_request) => codex_request,
+            Err(err) => {
+                let error = JSONRPCErrorError {
+                    code: INVALID_REQUEST_ERROR_CODE,
+                    message: format!("Invalid request: {err}"),
+                    data: None,
+                };
+                self.outgoing.send_error(request_id, error).await;
+                return;
+            }
+        };
 
-                        self.initialized = true;
-                        return;
+        match codex_request {
+            // Handle Initialize internally so CodexMessageProcessor does not have to concern
+            // itself with the `initialized` bool.
+            ClientRequest::Initialize { request_id, params } => {
+                if self.initialized {
+                    let error = JSONRPCErrorError {
+                        code: INVALID_REQUEST_ERROR_CODE,
+                        message: "Already initialized".to_string(),
+                        data: None,
+                    };
+                    self.outgoing.send_error(request_id, error).await;
+                    return;
+                } else {
+                    let ClientInfo {
+                        name,
+                        title: _title,
+                        version,
+                    } = params.client_info;
+                    let user_agent_suffix = format!("{name}; {version}");
+                    if let Ok(mut suffix) = USER_AGENT_SUFFIX.lock() {
+                        *suffix = Some(user_agent_suffix);
                     }
+
+                    let user_agent = get_codex_user_agent();
+                    let response = InitializeResponse { user_agent };
+                    self.outgoing.send_response(request_id, response).await;
+
+                    self.initialized = true;
+                    return;
                 }
-                _ => {
-                    if !self.initialized {
-                        let error = JSONRPCErrorError {
-                            code: INVALID_REQUEST_ERROR_CODE,
-                            message: "Not initialized".to_string(),
-                            data: None,
-                        };
-                        self.outgoing.send_error(request_id, error).await;
-                        return;
-                    }
+            }
+            _ => {
+                if !self.initialized {
+                    let error = JSONRPCErrorError {
+                        code: INVALID_REQUEST_ERROR_CODE,
+                        message: "Not initialized".to_string(),
+                        data: None,
+                    };
+                    self.outgoing.send_error(request_id, error).await;
+                    return;
                 }
             }
-
-            self.codex_message_processor
-                .process_request(codex_request)
-                .await;
-        } else {
-            let error = JSONRPCErrorError {
-                code: INVALID_REQUEST_ERROR_CODE,
-                message: "Invalid request".to_string(),
-                data: None,
-            };
-            self.outgoing.send_error(request_id, error).await;
         }
+
+        self.codex_message_processor
+            .process_request(codex_request)
+            .await;
     }
 
     pub(crate) async fn process_notification(&self, notification: JSONRPCNotification) {