gh-93627: Align Python implementation of pickle with C implementation of pickle (GH-103035)

If a method like __reduce_ex_ or __reduce__ is set to None, a TypeError is raised.

Lib/test/pickletester.py

@@ -2408,6 +2408,22 @@ class AbstractPickleTests:
             y = self.loads(s)
             self.assertEqual(y._reduce_called, 1)
 
+    def test_reduce_ex_None(self):
+        c = REX_None()
+        with self.assertRaises(TypeError):
+            self.dumps(c)
+
+    def test_reduce_None(self):
+        c = R_None()
+        with self.assertRaises(TypeError):
+            self.dumps(c)
+
+    def test_pickle_setstate_None(self):
+        c = C_None_setstate()
+        p = self.dumps(c)
+        with self.assertRaises(TypeError):
+            self.loads(p)
+
     @no_tracing
     def test_bad_getattr(self):
         # Issue #3514: crash when there is an infinite loop in __getattr__
@@ -3349,6 +3365,21 @@ class REX_state(object):
     def __reduce__(self):
         return type(self), (), self.state
 
+class REX_None:
+    """ Setting __reduce_ex__ to None should fail """
+    __reduce_ex__ = None
+
+class R_None:
+    """ Setting __reduce__ to None should fail """
+    __reduce__ = None
+
+class C_None_setstate:
+    """  Setting __setstate__ to None should fail """
+    def __getstate__(self):
+        return 1
+
+    __setstate__ = None
+
 
 # Test classes for newobj
 
@@ -3752,6 +3783,25 @@ class AbstractPicklerUnpicklerObjectTests:
                 unpickler = self.unpickler_class(f)
                 self.assertEqual(unpickler.load(), data)
 
+    def test_pickle_invalid_reducer_override(self):
+        # gh-103035
+        obj = object()
+
+        f = io.BytesIO()
+        class MyPickler(self.pickler_class):
+            pass
+        pickler = MyPickler(f)
+        pickler.dump(obj)
+
+        pickler.clear_memo()
+        pickler.reducer_override = None
+        with self.assertRaises(TypeError):
+            pickler.dump(obj)
+
+        pickler.clear_memo()
+        pickler.reducer_override = 10
+        with self.assertRaises(TypeError):
+            pickler.dump(obj)
 
 # Tests for dispatch_table attribute
 
@@ -3914,6 +3964,15 @@ class AbstractDispatchTableTests:
 
         self._test_dispatch_table(dumps, dt)
 
+    def test_dispatch_table_None_item(self):
+        # gh-93627
+        obj = object()
+        f = io.BytesIO()
+        pickler = self.pickler_class(f)
+        pickler.dispatch_table = {type(obj): None}
+        with self.assertRaises(TypeError):
+            pickler.dump(obj)
+
     def _test_dispatch_table(self, dumps, dispatch_table):
         def custom_load_dump(obj):
             return pickle.loads(dumps(obj, 0))