gh-125767: Fix pickling and copying of super objects (GH-125781)

Previously, copying a super object returned a copy of the instance
invoking super(). Pickling a super object could pickle the instance
invoking super() or fail, depending on its type and protocol.

Now deep copying returns a new super object and pickling pickles the super
object. Shallow copying returns the same super object.

3 files changed, 76 insertions, 1 deletions

diff --git a/Lib/copy.py b/Lib/copy.py
index a79976d..f27e109 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -106,7 +106,7 @@ for t in (types.NoneType, int, float, bool, complex, str, tuple,
           bytes, frozenset, type, range, slice, property,
           types.BuiltinFunctionType, types.EllipsisType,
           types.NotImplementedType, types.FunctionType, types.CodeType,
-          weakref.ref):
+          weakref.ref, super):
     d[t] = _copy_immutable
 
 d[list] = list.copy
diff --git a/Lib/copyreg.py b/Lib/copyreg.py
index 5783924..17c5dde 100644
--- a/Lib/copyreg.py
+++ b/Lib/copyreg.py
@@ -36,6 +36,11 @@ def pickle_union(obj):
 
 pickle(type(int | str), pickle_union)
 
+def pickle_super(obj):
+    return super, (obj.__thisclass__, obj.__self__)
+
+pickle(super, pickle_super)
+
 # Support for pickling new-style objects
 
 def _reconstructor(cls, base, state):
diff --git a/Lib/test/test_super.py b/Lib/test/test_super.py
index 1222ec6..1490166 100644
--- a/Lib/test/test_super.py
+++ b/Lib/test/test_super.py
@@ -1,5 +1,7 @@
 """Unit tests for zero-argument super() & related machinery."""
 
+import copy
+import pickle
 import textwrap
 import threading
 import unittest
@@ -539,6 +541,74 @@ class TestSuper(unittest.TestCase):
         for thread in threads:
             thread.join()
 
+    def test_special_methods(self):
+        for e in E(), E:
+            s = super(C, e)
+            self.assertEqual(s.__reduce__, e.__reduce__)
+            self.assertEqual(s.__reduce_ex__, e.__reduce_ex__)
+            self.assertEqual(s.__getstate__, e.__getstate__)
+            self.assertFalse(hasattr(s, '__getnewargs__'))
+            self.assertFalse(hasattr(s, '__getnewargs_ex__'))
+            self.assertFalse(hasattr(s, '__setstate__'))
+            self.assertFalse(hasattr(s, '__copy__'))
+            self.assertFalse(hasattr(s, '__deepcopy__'))
+
+    def test_pickling(self):
+        e = E()
+        e.x = 1
+        s = super(C, e)
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(proto=proto):
+                u = pickle.loads(pickle.dumps(s, proto))
+                self.assertEqual(u.f(), s.f())
+                self.assertIs(type(u), type(s))
+                self.assertIs(type(u.__self__), E)
+                self.assertEqual(u.__self__.x, 1)
+                self.assertIs(u.__thisclass__, C)
+                self.assertIs(u.__self_class__, E)
+
+        s = super(C, E)
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(proto=proto):
+                u = pickle.loads(pickle.dumps(s, proto))
+                self.assertEqual(u.cm(), s.cm())
+                self.assertEqual(u.f, s.f)
+                self.assertIs(type(u), type(s))
+                self.assertIs(u.__self__, E)
+                self.assertIs(u.__thisclass__, C)
+                self.assertIs(u.__self_class__, E)
+
+    def test_shallow_copying(self):
+        s = super(C, E())
+        self.assertIs(copy.copy(s), s)
+        s = super(C, E)
+        self.assertIs(copy.copy(s), s)
+
+    def test_deep_copying(self):
+        e = E()
+        e.x = [1]
+        s = super(C, e)
+        u = copy.deepcopy(s)
+        self.assertEqual(u.f(), s.f())
+        self.assertIs(type(u), type(s))
+        self.assertIsNot(u, s)
+        self.assertIs(type(u.__self__), E)
+        self.assertIsNot(u.__self__, e)
+        self.assertIsNot(u.__self__.x, e.x)
+        self.assertEqual(u.__self__.x, [1])
+        self.assertIs(u.__thisclass__, C)
+        self.assertIs(u.__self_class__, E)
+
+        s = super(C, E)
+        u = copy.deepcopy(s)
+        self.assertEqual(u.cm(), s.cm())
+        self.assertEqual(u.f, s.f)
+        self.assertIsNot(u, s)
+        self.assertIs(type(u), type(s))
+        self.assertIs(u.__self__, E)
+        self.assertIs(u.__thisclass__, C)
+        self.assertIs(u.__self_class__, E)
+
 
 if __name__ == "__main__":
     unittest.main()