gh-103092: Isolate _pickle module (#102982)

Co-authored-by: Mohamed Koubaa <[email protected]>
Co-authored-by: Kumar Aditya <[email protected]>

Lib/test/test_pickle.py

@@ -293,6 +293,34 @@ class CustomCPicklerClass(_pickle.Pickler, AbstractCustomPicklerClass):
             pass
         pickler_class = CustomCPicklerClass
 
+    @support.cpython_only
+    class HeapTypesTests(unittest.TestCase):
+        def setUp(self):
+            pickler = _pickle.Pickler(io.BytesIO())
+            unpickler = _pickle.Unpickler(io.BytesIO())
+
+            self._types = (
+                _pickle.Pickler,
+                _pickle.Unpickler,
+                type(pickler.memo),
+                type(unpickler.memo),
+
+                # We cannot test the _pickle.Pdata;
+                # there's no way to get to it.
+            )
+
+        def test_have_gc(self):
+            import gc
+            for tp in self._types:
+                with self.subTest(tp=tp):
+                    self.assertTrue(gc.is_tracked(tp))
+
+        def test_immutable(self):
+            for tp in self._types:
+                with self.subTest(tp=tp):
+                    with self.assertRaisesRegex(TypeError, "immutable"):
+                        tp.foo = "bar"
+
     @support.cpython_only
     class SizeofTests(unittest.TestCase):
         check_sizeof = support.check_sizeof

Misc/NEWS.d/next/Core and Builtins/2020-07-04-09-04-41.bpo-1635741.ZsP31Y.rst

@@ -0,0 +1 @@
+Adapt :mod:`!_pickle` to :pep:`687`. Patch by Mohamed Koubaa and Erlend Aasland.