😏

evals/codex-harness/fixture/SPEC.md

@@ -0,0 +1,4 @@
+# Deep merge contract
+
+`merge_settings(base, overlay)` returns a fresh mapping. Nested mappings merge recursively; overlay scalars replace base values; no input or nested output may be mutated or aliased.
+

evals/codex-harness/fixture/settings.py

@@ -0,0 +1,12 @@
+from collections.abc import Mapping
+from typing import Any
+
+
+def merge_settings(base: Mapping[str, Any], overlay: Mapping[str, Any]) -> dict[str, Any]:
+    result = dict(base)
+    for key, value in overlay.items():
+        if isinstance(value, Mapping) and isinstance(result.get(key), Mapping):
+            result[key].update(value)
+        else:
+            result[key] = value
+    return result

evals/codex-harness/fixture/test_settings.py

@@ -0,0 +1,23 @@
+import unittest
+
+from settings import merge_settings
+
+
+class MergeSettingsTests(unittest.TestCase):
+    def test_recursive_merge(self):
+        self.assertEqual(
+            merge_settings({"s": {"host": "x", "port": 80}}, {"s": {"port": 443}}),
+            {"s": {"host": "x", "port": 443}},
+        )
+
+    def test_inputs_and_outputs_do_not_alias(self):
+        base = {"s": {"host": "x"}, "flags": {"safe": True}}
+        overlay = {"s": {"port": 443}}
+        merged = merge_settings(base, overlay)
+        merged["s"]["host"] = "changed"
+        merged["flags"]["safe"] = False
+        self.assertEqual(base, {"s": {"host": "x"}, "flags": {"safe": True}})
+
+
+if __name__ == "__main__":
+    unittest.main()