From 3fbbd58c28b9a519d255b1cd7f359c5144109286 Mon Sep 17 00:00:00 2001
From: "Jeong, YunWon" <jeong@youknowone.org>
Date: Wed, 4 Mar 2026 18:44:27 +0900
Subject: [PATCH] Restore defaultdict fallback and update test markers

---
 Lib/collections/__init__.py     |  3 +-
 Lib/collections/_defaultdict.py | 58 +++++++++++++++++++++++++++++++++
 Lib/test/test_collections.py    |  4 +--
 Lib/test/test_deque.py          |  6 ++--
 4 files changed, 65 insertions(+), 6 deletions(-)
 create mode 100644 Lib/collections/_defaultdict.py

diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
index 803de0c67..3d3bbd7a3 100644
--- a/Lib/collections/__init__.py
+++ b/Lib/collections/__init__.py
@@ -57,7 +57,8 @@ except ImportError:
 try:
     from _collections import defaultdict
 except ImportError:
-    pass
+    # TODO: RUSTPYTHON - implement defaultdict in Rust
+    from ._defaultdict import defaultdict
 
 heapq = None  # Lazily imported
 
diff --git a/Lib/collections/_defaultdict.py b/Lib/collections/_defaultdict.py
new file mode 100644
index 000000000..b9c6c4961
--- /dev/null
+++ b/Lib/collections/_defaultdict.py
@@ -0,0 +1,58 @@
+from reprlib import recursive_repr as _recursive_repr
+
+class defaultdict(dict):
+    def __init__(self, *args, **kwargs):
+        if len(args) >= 1:
+            default_factory = args[0]
+            if default_factory is not None and not callable(default_factory):
+                raise TypeError("first argument must be callable or None")
+            args = args[1:]
+        else:
+            default_factory = None
+        super().__init__(*args, **kwargs)
+        self.default_factory = default_factory
+
+    def __missing__(self, key):
+        if self.default_factory is not None:
+            val = self.default_factory()
+        else:
+            raise KeyError(key)
+        self[key] = val
+        return val
+
+    @_recursive_repr()
+    def __repr_factory(factory):
+        return repr(factory)
+
+    def __repr__(self):
+        return f"{type(self).__name__}({defaultdict.__repr_factory(self.default_factory)}, {dict.__repr__(self)})"
+
+    def copy(self):
+        return type(self)(self.default_factory, self)
+
+    __copy__ = copy
+
+    def __reduce__(self):
+        if self.default_factory is not None:
+            args = self.default_factory,
+        else:
+            args = ()
+        return type(self), args, None, None, iter(self.items())
+
+    def __or__(self, other):
+        if not isinstance(other, dict):
+            return NotImplemented
+
+        new = defaultdict(self.default_factory, self)
+        new.update(other)
+        return new
+
+    def __ror__(self, other):
+        if not isinstance(other, dict):
+            return NotImplemented
+
+        new = defaultdict(self.default_factory, other)
+        new.update(self)
+        return new
+
+defaultdict.__module__ = 'collections'
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 0ed51c9f1..26d0dcb65 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -262,7 +262,7 @@ class TestChainMap(unittest.TestCase):
         d = c.new_child(b=20, c=30)
         self.assertEqual(d.maps, [{'b': 20, 'c': 30}, {'a': 1, 'b': 2}])
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: <class 'test.test_collections.TestChainMap.test_union_operators.<locals>.Subclass'> is not <class 'collections.ChainMap'>
     def test_union_operators(self):
         cm1 = ChainMap(dict(a=1, b=2), dict(c=3, d=4))
         cm2 = ChainMap(dict(a=10, e=5), dict(b=20, d=4))
@@ -2029,7 +2029,7 @@ class TestCollectionABCs(ABCTestCase):
         self.assertEqual(len(mss), len(mss2))
         self.assertEqual(list(mss), list(mss2))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: TypeError not raised
     def test_illegal_patma_flags(self):
         with self.assertRaises(TypeError):
             class Both(Collection):
diff --git a/Lib/test/test_deque.py b/Lib/test/test_deque.py
index cd7fc8afd..f798ab4b6 100644
--- a/Lib/test/test_deque.py
+++ b/Lib/test/test_deque.py
@@ -726,7 +726,7 @@ class TestBasic(unittest.TestCase):
             d.append(1)
             gc.collect()
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: False is not true : Cycle was not collected
     def test_container_iterator(self):
         # Bug #3680: tp_traverse was not implemented for deque iterator objects
         class C(object):
@@ -817,7 +817,7 @@ class TestSubclass(unittest.TestCase):
         d.clear()
         self.assertEqual(len(d), 0)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AttributeError: 'Deque' object has no attribute 'x'
     def test_copy_pickle(self):
         for cls in Deque, DequeWithSlots:
             for d in cls('abc'), cls('abcde', maxlen=4):
@@ -842,7 +842,7 @@ class TestSubclass(unittest.TestCase):
                     self.assertEqual(e.z, d.z)
                     self.assertNotHasAttr(e, 'y')
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AttributeError: 'Deque' object has no attribute 'x'
     def test_pickle_recursive(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             for d in Deque('abc'), Deque('abc', 3):