bpo-34320: Fix dict(o) didn't copy order of dict subclass (pythonGH-8624)

When dict subclass overrides order (`__iter__()`, `keys()`, and `items()`), `dict(o)` should use it instead of dict ordering. https://bugs.python.org/issue34320

Author: methane

Lib/test/test_builtin.py

@@ -1968,6 +1968,15 @@ class B:
  with self.assertRaises(TypeError):
  type('A', (B,), {'__slots__': '__weakref__'})
 
+ def test_namespace_order(self):
+ # bpo-34320: namespace should preserve order
+ od = collections.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 load_tests(loader, tests, pattern):
  from doctest import DocTestSuite

Lib/test/test_call.py

@@ -9,6 +9,23 @@
 import collections
 import itertools
 
+
+class FunctionCalls(unittest.TestCase):
+
+ def test_kwargs_order(self):
+ # bpo-34320: **kwargs should preserve order of passed OrderedDict
+ od = collections.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)
+
+
 # The test cases here cover several paths through the function calling
 # code. They depend on the METH_XXX flag that is used to define a C
 # function, which can't be verified from Python. If the METH_XXX decl

Lib/test/test_dict.py

@@ -1222,6 +1222,36 @@ def iter_and_mutate():
 
  self.assertRaises(RuntimeError, iter_and_mutate)
 
+ def test_dict_copy_order(self):
+ # bpo-34320
+ od = collections.OrderedDict([('a', 1), ('b', 2)])
+ od.move_to_end('a')
+ expected = list(od.items())
+
+ copy = dict(od)
+ self.assertEqual(list(copy.items()), expected)
+
+ # dict subclass doesn't override __iter__
+ class CustomDict(dict):
+ pass
+
+ pairs = [('a', 1), ('b', 2), ('c', 3)]
+
+ d = CustomDict(pairs)
+ self.assertEqual(pairs, list(dict(d).items()))
+
+ class CustomReversedDict(dict):
+ def keys(self):
+ return reversed(list(dict.keys(self)))
+
+ __iter__ = keys
+
+ def items(self):
+ return reversed(dict.items(self))
+
+ d = CustomReversedDict(pairs)
+ self.assertEqual(pairs[::-1], list(dict(d).items()))
+
 
 class CAPITest(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 */