Fix serve trace empty match to return 200 with empty JSON result

src/server/handlers.rs

@@ -447,13 +447,20 @@ struct DetailQuery {
 async fn trace(
     State(state): State<AppState>,
     Query(query): Query<TraceQuery>,
-) -> Result<impl IntoResponse, StatusCode> {
+) -> Json<Value> {
     let store = state.store();
     let matches = store.search_nodes(&query.from);
     let graph = state.graph();
 
     if matches.is_empty() {
-        return Err(StatusCode::NOT_FOUND);
+        return Json(serde_json::json!({
+            "target": null,
+            "callers": [],
+            "callees": [],
+            "caller_count": 0,
+            "callee_count": 0,
+            "truncated": false,
+        }));
     }
 
     let (start_idx, _) = &matches[0];
@@ -475,7 +482,7 @@ async fn trace(
         "truncated": visited >= max_nodes,
     });
 
-    Ok(Json(result))
+    Json(result)
 }
 
 async fn execute_query(

tests/serve_api.rs

@@ -201,4 +201,24 @@ mod tests {
         let json: serde_json::Value = serde_json::from_str(&body).unwrap();
         assert_eq!(json["total"], 0);
     }
+
+    #[test]
+    fn test_serve_trace_empty_match_returns_200() {
+        let port = 19883;
+        let mut child = start_server(port);
+
+        let (status, body) = get(
+            port,
+            "/api/v1/trace?from=nonexistent_symbol_xyz_123",
+        );
+        stop_server(&mut child);
+
+        assert_eq!(status, 200);
+        let json: serde_json::Value = serde_json::from_str(&body).unwrap();
+        assert!(json["target"].is_null());
+        assert_eq!(json["callers"], serde_json::json!([]));
+        assert_eq!(json["callees"], serde_json::json!([]));
+        assert_eq!(json["caller_count"], 0);
+        assert_eq!(json["callee_count"], 0);
+    }
 }