fix(dumpkit): preserve renamed builtin keys in fields() (#2733)

pcapkit/dumpkit/common.py

@@ -440,11 +440,14 @@ def fields(info: 'Info | MultiDict[Any, Any]') -> 'dict[Any, Any]':
             extension header, maps to the :class:`list` of all its values, in
             order (GitHub issue :issue:`1484`). The values are left as they
             are, so each comes back through :meth:`DictDumper.object_hook` when
-            written. The keys :func:`excluded` names are left out.
+            The keys :func:`excluded` names are left out, while a key
+            renamed for clashing with a builtin name is kept under its original
+            name (:issue:`2733`).
 
         """
         skip = excluded(info)
-        pairs = [(key, val) for key, val in info.items(multi=True) if key not in skip]
+        keymap = getattr(info, '__map__', {})
+        pairs = [(key, val) for key, val in info.items(multi=True) if keymap.get(key, key) not in skip]
         counts = collections.Counter(key for key, _ in pairs)
         result = {}  # type: dict[Any, Any]
         for key, val in pairs:

tests/dumpkit/test_common_unit.py

@@ -225,6 +225,23 @@ def test_make_dumper_object_hook_conversions_and_fallbacks(self) -> None:
         dumper._append_fallback(123, file)
         self.assertEqual(file.getvalue(), "{'base': '123'}")
 
+    def test_make_dumper_dumps_renamed_builtin_key(self) -> None:
+        """A key renamed for clashing with a builtin is kept under its original name (:issue:`2733`)."""
+        from pcapkit.corekit.infoclass import Info
+        from pcapkit.dumpkit.common import make_dumper
+        from pcapkit.foundation.reassembly.data.tcp import Datagram
+
+        Dumper = make_dumper(BaseDumper)
+        dumper = Dumper()
+
+        info = Info(items='catalog', normal='value')
+        self.assertEqual(dumper.object_hook(info), {'items': 'catalog', 'normal': 'value'})
+
+        datagram = Datagram(True, 'tcp-id', (0,), b'header', b'payload', b'raw_packet', [])
+        dumped = dumper.object_hook(datagram)
+        self.assertIn('packet', dumped)
+        self.assertEqual(dumped['packet'], b'raw_packet')
+
     def test_make_dumper_object_hook_leaves_strings_and_enum_renderings_unescaped(self) -> None:
         """GitHub issue #772: escaping is now the writer's own job, not this hook's.