bpo-34320: Fix dict(o) didn't copy order of dict subclass

Lib/test/test_ordered_dict.py

@@ -650,6 +650,41 @@ def test_free_after_iterating(self):
         support.check_free_after_iterating(self, lambda d: iter(d.values()), self.OrderedDict)
         support.check_free_after_iterating(self, lambda d: iter(d.items()), self.OrderedDict)
 
+    # TODO: This test is relating to PEP 468.
+    # Move this test to somewhere more appropriate.
+    def test_kwargs_order(self):
+        # bpo-34320
+        od = self.OrderedDict([('a', 1), ('b', 2)])
+        od.move_to_end('a')
+        expected = list(od.items())
+
+        def fn(**kw):
+            return kw
+
+        res = fn(**od)
+        self.assertIsInstance(res, dict)
+        self.assertEqual(list(res.items()), expected)
+
+    # TODO: This test is relating to PEP 520.
+    # Move this test to somewhere more appropriate.
+    def test_type_namespace_order(self):
+        # bpo-34320
+        od = self.OrderedDict([('a', 1), ('b', 2)])
+        od.move_to_end('a')
+        expected = list(od.items())
+
+        C = type('C', (), od)
+        self.assertEqual(list(C.__dict__.items())[:2], [('b', 2), ('a', 1)])
+
+    def test_dict_copy_order(self):
+        # bpo-34320
+        od = self.OrderedDict([('a', 1), ('b', 2)])
+        od.move_to_end('a')
+        expected = list(od.items())
+
+        copy = dict(od)
+        self.assertEqual(list(copy.items()), expected)
+
 
 class PurePythonOrderedDictTests(OrderedDictTests, unittest.TestCase):
 

Misc/NEWS.d/next/Core and Builtins/2018-08-02-22-34-59.bpo-34320.hNshAA.rst

@@ -0,0 +1 @@
+Fix ``dict(od)`` didn't copy iteration order of OrderedDict.

Objects/dictobject.c

@@ -235,6 +235,8 @@ static Py_ssize_t lookdict_split(PyDictObject *mp, PyObject *key,
 
 static int dictresize(PyDictObject *mp, Py_ssize_t minused);
 
+static PyObject* dict_iter(PyDictObject *dict);
+
 /*Global counter used to set ma_version_tag field of dictionary.
  * It is incremented each time that a dictionary is created and each
  * time that a dictionary is modified. */
@@ -2379,7 +2381,7 @@ dict_merge(PyObject *a, PyObject *b, int override)
         return -1;
     }
     mp = (PyDictObject*)a;
-    if (PyDict_Check(b)) {
+    if (PyDict_Check(b) && (Py_TYPE(b)->tp_iter == (getiterfunc)dict_iter)) {
         other = (PyDictObject*)b;
         if (other == mp || other->ma_used == 0)
             /* a.update(a) or a.update({}); nothing to do */