fix(trace): keep JSON export metadata reusable

openevolve/utils/trace_export_utils.py

@@ -54,7 +54,7 @@ def export_traces_json(
     Args:
         traces: List of trace objects with to_dict() method
         output_path: Path to save the JSON file
-        metadata: Optional metadata to include in the output
+        metadata: Optional metadata to include in the output, without modifying the caller's dict
     """
     output_path = Path(output_path)
     output_path.parent.mkdir(parents=True, exist_ok=True)
@@ -68,7 +68,7 @@ def export_traces_json(
             trace_dicts.append(trace)
 
     # Build output structure
-    output_data = {"metadata": metadata or {}, "traces": trace_dicts}
+    output_data = {"metadata": dict(metadata or {}), "traces": trace_dicts}
 
     # Add default metadata
     output_data["metadata"].setdefault("total_traces", len(trace_dicts))

tests/test_trace_export_json.py

@@ -0,0 +1,56 @@
+"""Regression tests for JSON trace export metadata ownership."""
+
+import json
+import tempfile
+import unittest
+from pathlib import Path
+from unittest.mock import patch
+
+from openevolve.utils.trace_export_utils import export_traces_json
+
+
+class TestJsonExportMetadata(unittest.TestCase):
+    def test_reusing_metadata_exports_fresh_statistics(self):
+        metadata = {"run": "example"}
+        with tempfile.TemporaryDirectory() as directory:
+            first_path = Path(directory) / "first.json"
+            second_path = Path(directory) / "second.json"
+            with patch("openevolve.utils.trace_export_utils.time") as clock:
+                clock.time.side_effect = [1000.0, 2000.0]
+                export_traces_json([{"id": "one"}], first_path, metadata)
+                export_traces_json([{"id": "one"}, {"id": "two"}], second_path, metadata)
+
+            first = json.loads(first_path.read_text())
+            second = json.loads(second_path.read_text())
+
+        self.assertEqual(first["metadata"]["total_traces"], len(first["traces"]))
+        self.assertEqual(first["metadata"]["exported_at"], 1000.0)
+        self.assertEqual(second["metadata"]["total_traces"], len(second["traces"]))
+        self.assertEqual(second["metadata"]["exported_at"], 2000.0)
+        self.assertEqual(metadata, {"run": "example"})
+
+    def test_explicit_statistics_remain_overridable(self):
+        metadata = {"run": "example", "total_traces": 42, "exported_at": 123.0}
+        with tempfile.TemporaryDirectory() as directory:
+            path = Path(directory) / "traces.json"
+            export_traces_json([{"id": "one"}], path, metadata)
+            exported = json.loads(path.read_text())
+
+        self.assertEqual(exported["metadata"], metadata)
+        self.assertEqual(exported["traces"], [{"id": "one"}])
+
+    def test_missing_and_empty_metadata_get_default_statistics(self):
+        for metadata in (None, {}):
+            with self.subTest(metadata=metadata), tempfile.TemporaryDirectory() as directory:
+                path = Path(directory) / "traces.json"
+                with patch("openevolve.utils.trace_export_utils.time") as clock:
+                    clock.time.return_value = 1000.0
+                    export_traces_json([], path, metadata)
+                exported = json.loads(path.read_text())
+
+            self.assertEqual(exported["metadata"], {"total_traces": 0, "exported_at": 1000.0})
+            self.assertEqual(exported["traces"], [])
+
+
+if __name__ == "__main__":
+    unittest.main()