gh-125631: Enable setting persistent_id and persistent_load of pickler and unpickler (GH-125752)

pickle.Pickler.persistent_id and pickle.Unpickler.persistent_load can
again be overridden as instance attributes.

Lib/test/test_pickle.py

@@ -250,6 +250,84 @@ class PyIdPersPicklerTests(AbstractIdentityPersistentPicklerTests,
             self.assertEqual(unpickler.load(), 'abc')
             self.assertEqual(called, ['abc'])
 
+    def test_pickler_instance_attribute(self):
+        def persistent_id(obj):
+            called.append(obj)
+            return obj
+
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            f = io.BytesIO()
+            pickler = self.pickler(f, proto)
+            called = []
+            old_persistent_id = pickler.persistent_id
+            pickler.persistent_id = persistent_id
+            self.assertEqual(pickler.persistent_id, persistent_id)
+            pickler.dump('abc')
+            self.assertEqual(called, ['abc'])
+            self.assertEqual(self.loads(f.getvalue()), 'abc')
+            del pickler.persistent_id
+            self.assertEqual(pickler.persistent_id, old_persistent_id)
+
+    def test_unpickler_instance_attribute(self):
+        def persistent_load(pid):
+            called.append(pid)
+            return pid
+
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            unpickler = self.unpickler(io.BytesIO(self.dumps('abc', proto)))
+            called = []
+            old_persistent_load = unpickler.persistent_load
+            unpickler.persistent_load = persistent_load
+            self.assertEqual(unpickler.persistent_load, persistent_load)
+            self.assertEqual(unpickler.load(), 'abc')
+            self.assertEqual(called, ['abc'])
+            del unpickler.persistent_load
+            self.assertEqual(unpickler.persistent_load, old_persistent_load)
+
+    def test_pickler_super_instance_attribute(self):
+        class PersPickler(self.pickler):
+            def persistent_id(subself, obj):
+                raise AssertionError('should never be called')
+            def _persistent_id(subself, obj):
+                called.append(obj)
+                self.assertIsNone(super().persistent_id(obj))
+                return obj
+
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            f = io.BytesIO()
+            pickler = PersPickler(f, proto)
+            called = []
+            old_persistent_id = pickler.persistent_id
+            pickler.persistent_id = pickler._persistent_id
+            self.assertEqual(pickler.persistent_id, pickler._persistent_id)
+            pickler.dump('abc')
+            self.assertEqual(called, ['abc'])
+            self.assertEqual(self.loads(f.getvalue()), 'abc')
+            del pickler.persistent_id
+            self.assertEqual(pickler.persistent_id, old_persistent_id)
+
+    def test_unpickler_super_instance_attribute(self):
+        class PersUnpickler(self.unpickler):
+            def persistent_load(subself, pid):
+                raise AssertionError('should never be called')
+            def _persistent_load(subself, pid):
+                called.append(pid)
+                with self.assertRaises(self.persistent_load_error):
+                    super().persistent_load(pid)
+                return pid
+
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            unpickler = PersUnpickler(io.BytesIO(self.dumps('abc', proto)))
+            called = []
+            old_persistent_load = unpickler.persistent_load
+            unpickler.persistent_load = unpickler._persistent_load
+            self.assertEqual(unpickler.persistent_load, unpickler._persistent_load)
+            self.assertEqual(unpickler.load(), 'abc')
+            self.assertEqual(called, ['abc'])
+            del unpickler.persistent_load
+            self.assertEqual(unpickler.persistent_load, old_persistent_load)
+
+
 class PyPicklerUnpicklerObjectTests(AbstractPicklerUnpicklerObjectTests, unittest.TestCase):
 
     pickler_class = pickle._Pickler
@@ -373,7 +451,7 @@ if has_c_implementation:
         check_sizeof = support.check_sizeof
 
         def test_pickler(self):
-            basesize = support.calcobjsize('6P2n3i2n3i2P')
+            basesize = support.calcobjsize('7P2n3i2n3i2P')
             p = _pickle.Pickler(io.BytesIO())
             self.assertEqual(object.__sizeof__(p), basesize)
             MT_size = struct.calcsize('3nP0n')
@@ -390,7 +468,7 @@ if has_c_implementation:
                 0)  # Write buffer is cleared after every dump().
 
         def test_unpickler(self):
-            basesize = support.calcobjsize('2P2nP 2P2n2i5P 2P3n8P2n2i')
+            basesize = support.calcobjsize('2P2n2P 2P2n2i5P 2P3n8P2n2i')
             unpickler = _pickle.Unpickler
             P = struct.calcsize('P')  # Size of memo table entry.
             n = struct.calcsize('n')  # Size of mark table entry.

Misc/NEWS.d/next/Library/2024-10-19-11-06-06.gh-issue-125631.BlhVvR.rst

@@ -0,0 +1,4 @@
+Restore ability to set :attr:`~pickle.Pickler.persistent_id` and
+:attr:`~pickle.Unpickler.persistent_load` attributes of instances of the
+:class:`!Pickler` and :class:`!Unpickler` classes in the :mod:`pickle`
+module.

Modules/_pickle.c

@@ -613,6 +613,7 @@ typedef struct PicklerObject {
                                    objects to support self-referential objects
                                    pickling. */
     PyObject *persistent_id;    /* persistent_id() method, can be NULL */
+    PyObject *persistent_id_attr; /* instance attribute, can be NULL */
     PyObject *dispatch_table;   /* private dispatch_table, can be NULL */
     PyObject *reducer_override; /* hook for invoking user-defined callbacks
                                    instead of save_global when pickling
@@ -655,6 +656,7 @@ typedef struct UnpicklerObject {
     size_t memo_len;        /* Number of objects in the memo */
 
     PyObject *persistent_load;  /* persistent_load() method, can be NULL. */
+    PyObject *persistent_load_attr;  /* instance attribute, can be NULL. */
 
     Py_buffer buffer;
     char *input_buffer;
@@ -1108,6 +1110,7 @@ _Pickler_New(PickleState *st)
 
     self->memo = memo;
     self->persistent_id = NULL;
+    self->persistent_id_attr = NULL;
     self->dispatch_table = NULL;
     self->reducer_override = NULL;
     self->write = NULL;
@@ -1606,6 +1609,7 @@ _Unpickler_New(PyObject *module)
     self->memo_size = MEMO_SIZE;
     self->memo_len = 0;
     self->persistent_load = NULL;
+    self->persistent_load_attr = NULL;
     memset(&self->buffer, 0, sizeof(Py_buffer));
     self->input_buffer = NULL;
     self->input_line = NULL;
@@ -5092,6 +5096,33 @@ Pickler_set_memo(PicklerObject *self, PyObject *obj, void *Py_UNUSED(ignored))
     return -1;
 }
 
+static PyObject *
+Pickler_getattr(PyObject *self, PyObject *name)
+{
+    if (PyUnicode_Check(name)
+        && PyUnicode_EqualToUTF8(name, "persistent_id")
+        && ((PicklerObject *)self)->persistent_id_attr)
+    {
+        return Py_NewRef(((PicklerObject *)self)->persistent_id_attr);
+    }
+
+    return PyObject_GenericGetAttr(self, name);
+}
+
+static int
+Pickler_setattr(PyObject *self, PyObject *name, PyObject *value)
+{
+    if (PyUnicode_Check(name)
+        && PyUnicode_EqualToUTF8(name, "persistent_id"))
+    {
+        Py_XINCREF(value);
+        Py_XSETREF(((PicklerObject *)self)->persistent_id_attr, value);
+        return 0;
+    }
+
+    return PyObject_GenericSetAttr(self, name, value);
+}
+
 static PyMemberDef Pickler_members[] = {
     {"bin", Py_T_INT, offsetof(PicklerObject, bin)},
     {"fast", Py_T_INT, offsetof(PicklerObject, fast)},
@@ -5107,6 +5138,8 @@ static PyGetSetDef Pickler_getsets[] = {
 
 static PyType_Slot pickler_type_slots[] = {
     {Py_tp_dealloc, Pickler_dealloc},
+    {Py_tp_getattro, Pickler_getattr},
+    {Py_tp_setattro, Pickler_setattr},
     {Py_tp_methods, Pickler_methods},
     {Py_tp_members, Pickler_members},
     {Py_tp_getset, Pickler_getsets},
@@ -7566,6 +7599,33 @@ Unpickler_set_memo(UnpicklerObject *self, PyObject *obj, void *Py_UNUSED(ignored
     return -1;
 }
 
+static PyObject *
+Unpickler_getattr(PyObject *self, PyObject *name)
+{
+    if (PyUnicode_Check(name)
+        && PyUnicode_EqualToUTF8(name, "persistent_load")
+        && ((UnpicklerObject *)self)->persistent_load_attr)
+    {
+        return Py_NewRef(((UnpicklerObject *)self)->persistent_load_attr);
+    }
+
+    return PyObject_GenericGetAttr(self, name);
+}
+
+static int
+Unpickler_setattr(PyObject *self, PyObject *name, PyObject *value)
+{
+    if (PyUnicode_Check(name)
+        && PyUnicode_EqualToUTF8(name, "persistent_load"))
+    {
+        Py_XINCREF(value);
+        Py_XSETREF(((UnpicklerObject *)self)->persistent_load_attr, value);
+        return 0;
+    }
+
+    return PyObject_GenericSetAttr(self, name, value);
+}
+
 static PyGetSetDef Unpickler_getsets[] = {
     {"memo", (getter)Unpickler_get_memo, (setter)Unpickler_set_memo},
     {NULL}
@@ -7574,6 +7634,8 @@ static PyGetSetDef Unpickler_getsets[] = {
 static PyType_Slot unpickler_type_slots[] = {
     {Py_tp_dealloc, Unpickler_dealloc},
     {Py_tp_doc, (char *)_pickle_Unpickler___init____doc__},
+    {Py_tp_getattro, Unpickler_getattr},
+    {Py_tp_setattro, Unpickler_setattr},
     {Py_tp_traverse, Unpickler_traverse},
     {Py_tp_clear, Unpickler_clear},
     {Py_tp_methods, Unpickler_methods},