bpo-38405: Make nested subclasses of typing.NamedTuple pickleable. (GH-16641)

Lib/test/test_typing.py

@@ -3468,6 +3468,9 @@ class NewTypeTests(BaseTestCase):
 
 
 class NamedTupleTests(BaseTestCase):
+    class NestedEmployee(NamedTuple):
+        name: str
+        cool: int
 
     def test_basics(self):
         Emp = NamedTuple('Emp', [('name', str), ('id', int)])
@@ -3587,14 +3590,25 @@ class XMethBad2(NamedTuple):
         with self.assertRaises(TypeError):
             NamedTuple('Emp', fields=[('name', str), ('id', int)])
 
-    def test_pickle(self):
+    def test_copy_and_pickle(self):
         global Emp  # pickle wants to reference the class by name
-        Emp = NamedTuple('Emp', [('name', str), ('id', int)])
-        jane = Emp('jane', 37)
-        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
-            z = pickle.dumps(jane, proto)
-            jane2 = pickle.loads(z)
-            self.assertEqual(jane2, jane)
+        Emp = NamedTuple('Emp', [('name', str), ('cool', int)])
+        for cls in Emp, CoolEmployee, self.NestedEmployee:
+            with self.subTest(cls=cls):
+                jane = cls('jane', 37)
+                for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+                    z = pickle.dumps(jane, proto)
+                    jane2 = pickle.loads(z)
+                    self.assertEqual(jane2, jane)
+                    self.assertIsInstance(jane2, cls)
+
+                jane2 = copy(jane)
+                self.assertEqual(jane2, jane)
+                self.assertIsInstance(jane2, cls)
+
+                jane2 = deepcopy(jane)
+                self.assertEqual(jane2, jane)
+                self.assertIsInstance(jane2, cls)
 
 
 class TypedDictTests(BaseTestCase):

Lib/typing.py

@@ -1593,7 +1593,7 @@ _prohibited = ('__new__', '__init__', '__slots__', '__getnewargs__',
                '_fields', '_field_defaults', '_field_types',
                '_make', '_replace', '_asdict', '_source')
 
-_special = ('__module__', '__name__', '__qualname__', '__annotations__')
+_special = ('__module__', '__name__', '__annotations__')
 
 
 class NamedTupleMeta(type):

Misc/NEWS.d/next/Library/2019-10-08-11-18-40.bpo-38405.0-7e7s.rst

+Nested subclasses of :class:`typing.NamedTuple` are now pickleable.