bpo-33462: Add __reversed__ to dict and dict views (GH-6827)

3 files changed, 80 insertions, 18 deletions

diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 0b7cb58..200e027 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -796,22 +796,21 @@ class TestOneTrickPonyABCs(ABCTestCase):
 
     def test_Reversible(self):
         # Check some non-reversibles
-        non_samples = [None, 42, 3.14, 1j, dict(), set(), frozenset()]
+        non_samples = [None, 42, 3.14, 1j, set(), frozenset()]
         for x in non_samples:
             self.assertNotIsInstance(x, Reversible)
             self.assertFalse(issubclass(type(x), Reversible), repr(type(x)))
         # Check some non-reversible iterables
-        non_reversibles = [dict().keys(), dict().items(), dict().values(),
-                           Counter(), Counter().keys(), Counter().items(),
-                           Counter().values(), _test_gen(),
-                           (x for x in []), iter([]), reversed([])]
+        non_reversibles = [_test_gen(), (x for x in []), iter([]), reversed([])]
         for x in non_reversibles:
             self.assertNotIsInstance(x, Reversible)
             self.assertFalse(issubclass(type(x), Reversible), repr(type(x)))
         # Check some reversible iterables
         samples = [bytes(), str(), tuple(), list(), OrderedDict(),
                    OrderedDict().keys(), OrderedDict().items(),
-                   OrderedDict().values()]
+                   OrderedDict().values(), Counter(), Counter().keys(),
+                   Counter().items(), Counter().values(), dict(),
+                   dict().keys(), dict().items(), dict().values()]
         for x in samples:
             self.assertIsInstance(x, Reversible)
             self.assertTrue(issubclass(type(x), Reversible), repr(type(x)))
@@ -1612,7 +1611,7 @@ class TestCollectionABCs(ABCTestCase):
         self.assertIsInstance(z, set)
         list(z)
         mymap['blue'] = 7               # Shouldn't affect 'z'
-        self.assertEqual(sorted(z), [('orange', 3), ('red', 5)])
+        self.assertEqual(z, {('orange', 3), ('red', 5)})
 
     def test_Sequence(self):
         for sample in [tuple, list, bytes, str]:
@@ -1767,10 +1766,10 @@ class TestCounter(unittest.TestCase):
         self.assertTrue(issubclass(Counter, Mapping))
         self.assertEqual(len(c), 3)
         self.assertEqual(sum(c.values()), 6)
-        self.assertEqual(sorted(c.values()), [1, 2, 3])
-        self.assertEqual(sorted(c.keys()), ['a', 'b', 'c'])
-        self.assertEqual(sorted(c), ['a', 'b', 'c'])
-        self.assertEqual(sorted(c.items()),
+        self.assertEqual(list(c.values()), [3, 2, 1])
+        self.assertEqual(list(c.keys()), ['a', 'b', 'c'])
+        self.assertEqual(list(c), ['a', 'b', 'c'])
+        self.assertEqual(list(c.items()),
                          [('a', 3), ('b', 2), ('c', 1)])
         self.assertEqual(c['b'], 2)
         self.assertEqual(c['z'], 0)
@@ -1784,7 +1783,7 @@ class TestCounter(unittest.TestCase):
         for i in range(5):
             self.assertEqual(c.most_common(i),
                              [('a', 3), ('b', 2), ('c', 1)][:i])
-        self.assertEqual(''.join(sorted(c.elements())), 'aaabbc')
+        self.assertEqual(''.join(c.elements()), 'aaabbc')
         c['a'] += 1         # increment an existing value
         c['b'] -= 2         # sub existing value to zero
         del c['c']          # remove an entry
@@ -1793,7 +1792,7 @@ class TestCounter(unittest.TestCase):
         c['e'] = -5         # directly assign a missing value
         c['f'] += 4         # add to a missing value
         self.assertEqual(c, dict(a=4, b=0, d=-2, e=-5, f=4))
-        self.assertEqual(''.join(sorted(c.elements())), 'aaaaffff')
+        self.assertEqual(''.join(c.elements()), 'aaaaffff')
         self.assertEqual(c.pop('f'), 4)
         self.assertNotIn('f', c)
         for i in range(3):
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index 90c0a31..71fffe3 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -1021,7 +1021,7 @@ class DictTest(unittest.TestCase):
             it = iter(data)
             d = pickle.dumps(it, proto)
             it = pickle.loads(d)
-            self.assertEqual(sorted(it), sorted(data))
+            self.assertEqual(list(it), list(data))
 
             it = pickle.loads(d)
             try:
@@ -1031,7 +1031,7 @@ class DictTest(unittest.TestCase):
             d = pickle.dumps(it, proto)
             it = pickle.loads(d)
             del data[drop]
-            self.assertEqual(sorted(it), sorted(data))
+            self.assertEqual(list(it), list(data))
 
     def test_itemiterator_pickling(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
@@ -1062,7 +1062,7 @@ class DictTest(unittest.TestCase):
             it = iter(data.values())
             d = pickle.dumps(it, proto)
             it = pickle.loads(d)
-            self.assertEqual(sorted(list(it)), sorted(list(data.values())))
+            self.assertEqual(list(it), list(data.values()))
 
             it = pickle.loads(d)
             drop = next(it)
@@ -1071,6 +1071,62 @@ class DictTest(unittest.TestCase):
             values = list(it) + [drop]
             self.assertEqual(sorted(values), sorted(list(data.values())))
 
+    def test_reverseiterator_pickling(self):
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            data = {1:"a", 2:"b", 3:"c"}
+            it = reversed(data)
+            d = pickle.dumps(it, proto)
+            it = pickle.loads(d)
+            self.assertEqual(list(it), list(reversed(data)))
+
+            it = pickle.loads(d)
+            try:
+                drop = next(it)
+            except StopIteration:
+                continue
+            d = pickle.dumps(it, proto)
+            it = pickle.loads(d)
+            del data[drop]
+            self.assertEqual(list(it), list(reversed(data)))
+
+    def test_reverseitemiterator_pickling(self):
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            data = {1:"a", 2:"b", 3:"c"}
+            # dictviews aren't picklable, only their iterators
+            itorg = reversed(data.items())
+            d = pickle.dumps(itorg, proto)
+            it = pickle.loads(d)
+            # note that the type of the unpickled iterator
+            # is not necessarily the same as the original.  It is
+            # merely an object supporting the iterator protocol, yielding
+            # the same objects as the original one.
+            # self.assertEqual(type(itorg), type(it))
+            self.assertIsInstance(it, collections.abc.Iterator)
+            self.assertEqual(dict(it), data)
+
+            it = pickle.loads(d)
+            drop = next(it)
+            d = pickle.dumps(it, proto)
+            it = pickle.loads(d)
+            del data[drop[0]]
+            self.assertEqual(dict(it), data)
+
+    def test_reversevaluesiterator_pickling(self):
+        for proto in range(pickle.HIGHEST_PROTOCOL):
+            data = {1:"a", 2:"b", 3:"c"}
+            # data.values() isn't picklable, only its iterator
+            it = reversed(data.values())
+            d = pickle.dumps(it, proto)
+            it = pickle.loads(d)
+            self.assertEqual(list(it), list(reversed(data.values())))
+
+            it = pickle.loads(d)
+            drop = next(it)
+            d = pickle.dumps(it, proto)
+            it = pickle.loads(d)
+            values = list(it) + [drop]
+            self.assertEqual(sorted(values), sorted(data.values()))
+
     def test_instance_dict_getattr_str_subclass(self):
         class Foo:
             def __init__(self, msg):
@@ -1222,6 +1278,13 @@ class DictTest(unittest.TestCase):
 
         self.assertRaises(RuntimeError, iter_and_mutate)
 
+    def test_reversed(self):
+        d = {"a": 1, "b": 2, "foo": 0, "c": 3, "d": 4}
+        del d["foo"]
+        r = reversed(d)
+        self.assertEqual(list(r), list('dcba'))
+        self.assertRaises(StopIteration, next, r)
+
     def test_dict_copy_order(self):
         # bpo-34320
         od = collections.OrderedDict([('a', 1), ('b', 2)])
diff --git a/Lib/test/test_enumerate.py b/Lib/test/test_enumerate.py
index e455ade..5785cb4 100644
--- a/Lib/test/test_enumerate.py
+++ b/Lib/test/test_enumerate.py
@@ -160,9 +160,9 @@ class TestReversed(unittest.TestCase, PickleTest):
                 raise StopIteration
             def __len__(self):
                 return 5
-        for data in 'abc', range(5), tuple(enumerate('abc')), A(), range(1,17,5):
+        for data in ('abc', range(5), tuple(enumerate('abc')), A(),
+                    range(1,17,5), dict.fromkeys('abcde')):
             self.assertEqual(list(data)[::-1], list(reversed(data)))
-        self.assertRaises(TypeError, reversed, {})
         # don't allow keyword arguments
         self.assertRaises(TypeError, reversed, [], a=1)