Distinguish read and deser errors in engine websocket

Fixes #2639

src/wasm-lib/kcl/src/engine/conn.rs

@@ -40,23 +40,49 @@ pub struct TcpRead {
     stream: futures::stream::SplitStream<tokio_tungstenite::WebSocketStream<reqwest::Upgraded>>,
 }
 
+/// Occurs when client couldn't read from the WebSocket to the engine.
+#[derive(Debug)]
+pub enum WebSocketReadError {
+    /// Could not read a message due to WebSocket errors.
+    Read(tokio_tungstenite::tungstenite::Error),
+    /// WebSocket message didn't contain a valid message that the KCL Executor could parse.
+    Deser(anyhow::Error),
+}
+
+impl From<anyhow::Error> for WebSocketReadError {
+    fn from(e: anyhow::Error) -> Self {
+        Self::Deser(e)
+    }
+}
+
 impl TcpRead {
-    pub async fn read(&mut self) -> Result<WebSocketResponse> {
+    pub async fn read(&mut self) -> std::result::Result<WebSocketResponse, WebSocketReadError> {
         let Some(msg) = self.stream.next().await else {
-            anyhow::bail!("Failed to read from websocket");
+            return Err(anyhow::anyhow!("Failed to read from WebSocket").into());
+        };
+        let msg = match msg {
+            Ok(msg) => msg,
+            Err(e) if matches!(e, tokio_tungstenite::tungstenite::Error::Protocol(_)) => {
+                return Err(WebSocketReadError::Read(e))
+            }
+            Err(e) => return Err(anyhow::anyhow!("Error reading from engine's WebSocket: {e}").into()),
         };
-        let msg: WebSocketResponse = match msg? {
-            WsMsg::Text(text) => serde_json::from_str(&text)?,
-            WsMsg::Binary(bin) => bson::from_slice(&bin)?,
-            other => anyhow::bail!("Unexpected websocket message from server: {}", other),
+        let msg: WebSocketResponse = match msg {
+            WsMsg::Text(text) => serde_json::from_str(&text)
+                .map_err(anyhow::Error::from)
+                .map_err(WebSocketReadError::from)?,
+            WsMsg::Binary(bin) => bson::from_slice(&bin)
+                .map_err(anyhow::Error::from)
+                .map_err(WebSocketReadError::from)?,
+            other => return Err(anyhow::anyhow!("Unexpected WebSocket message from engine API: {other}").into()),
         };
         Ok(msg)
     }
 }
 
 #[derive(Debug)]
 pub struct TcpReadHandle {
-    handle: Arc<tokio::task::JoinHandle<Result<()>>>,
+    handle: Arc<tokio::task::JoinHandle<Result<(), WebSocketReadError>>>,
 }
 
 impl Drop for TcpReadHandle {
@@ -150,7 +176,7 @@ impl EngineConnection {
                 match tcp_read.read().await {
                     Ok(ws_resp) => {
                         for e in ws_resp.errors.iter().flatten() {
-                            println!("got error message: {e}");
+                            println!("got error message: {} {}", e.error_code, e.message);
                         }
                         if let Some(id) = ws_resp.request_id {
                             responses_clone.insert(id, ws_resp.clone());