From 8b4e2e93d9b545f5888e2add50ed06c6df0a2ec9 Mon Sep 17 00:00:00 2001
From: njzjz-bot <njzjz.bot@gmail.com>
Date: Mon, 24 Aug 2026 03:10:37 +0800
Subject: [PATCH] fix: copy mutable defaults during normalization

Coding-Agent: Codex
Codex-Version: codex-cli 0.149.0
Model: gpt-5.6-sol
Reasoning-Effort: xhigh
---
 dargs/dargs.py           |  6 +++++-
 tests/test_normalizer.py | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/dargs/dargs.py b/dargs/dargs.py
index f067b01..0e5485e 100644
--- a/dargs/dargs.py
+++ b/dargs/dargs.py
@@ -665,7 +665,11 @@ def _assign_default(self, argdict: dict, path: list[str] | None = None) -> None:
             and self.optional
             and self.default is not _Flags.NONE
         ):
-            default = self.default if self.default != {} else _Flags.EMPTY_DICT
+            # Defaults belong to the schema and must not be shared with caller-owned
+            # normalized data. Deep-copying also protects nested mutable objects.
+            default = (
+                deepcopy(self.default) if self.default != {} else _Flags.EMPTY_DICT
+            )
             argdict[self.name] = default
 
     def _handle_empty_dict(self, argdict: dict, path: list[str] | None = None) -> None:
diff --git a/tests/test_normalizer.py b/tests/test_normalizer.py
index 9f9d995..64607b9 100644
--- a/tests/test_normalizer.py
+++ b/tests/test_normalizer.py
@@ -30,6 +30,26 @@ def make_arguments() -> list[Argument]:
         data = base.normalize_value({})
         self.assertDictEqual(data, {"bar": {}})
 
+    def test_mutable_defaults_are_copied(self) -> None:
+        """Mutating normalized defaults must not change later results or schemas."""
+        items = Argument("items", list, optional=True, default=[])
+        settings = Argument(
+            "settings",
+            dict,
+            optional=True,
+            default={"labels": []},
+        )
+        base = Argument("base", dict, [items, settings])
+
+        first = base.normalize_value({})
+        first["items"].append("changed")
+        first["settings"]["labels"].append("changed")
+        second = base.normalize_value({})
+
+        self.assertEqual(second, {"items": [], "settings": {"labels": []}})
+        self.assertEqual(items.default, [])
+        self.assertEqual(settings.default, {"labels": []})
+
     def test_alias(self) -> None:
         ca = Argument("Key1", int, alias=["Old1", "Old2"])
         beg = {"Old1": 1}