gh-141510, PEP 814: Add frozendict support to pickle

Lib/test/picklecommon.py

@@ -263,6 +263,17 @@ class MyFrozenSet(frozenset):
              MyStr, MyUnicode,
              MyTuple, MyList, MyDict, MySet, MyFrozenSet]
 
+try:
+    frozendict
+except NameError:
+    # Python 3.14 and older
+    pass
+else:
+    class MyFrozenDict(dict):
+        sample = frozendict({"a": 1, "b": 2})
+    myclasses.append(MyFrozenDict)
+
+
 # For test_newobj_overridden_new
 class MyIntWithNew(int):
     def __new__(cls, value):

Lib/test/pickletester.py

@@ -2839,11 +2839,13 @@ def test_recursive_multi(self):
             self.assertEqual(list(x[0].attr.keys()), [1])
             self.assertIs(x[0].attr[1], x)
 
-    def _test_recursive_collection_and_inst(self, factory, oldminproto=None):
+    def _test_recursive_collection_and_inst(self, factory, oldminproto=None,
+                                            minprotocol=0):
         if self.py_version < (3, 0):
             self.skipTest('"classic" classes are not interoperable with Python 2')
         # Mutable object containing a collection containing the original
         # object.
+        protocols = range(minprotocol, pickle.HIGHEST_PROTOCOL + 1)
         o = Object()
         o.attr = factory([o])
         t = type(o.attr)
@@ -2883,6 +2885,11 @@ def test_recursive_tuple_and_inst(self):
     def test_recursive_dict_and_inst(self):
         self._test_recursive_collection_and_inst(dict.fromkeys, oldminproto=0)
 
+    def test_recursive_frozendict_and_inst(self):
+        if self.py_version < (3, 15):
+            self.skipTest('need frozendict')
+        self._test_recursive_collection_and_inst(frozendict.fromkeys, minprotocol=2)
+
     def test_recursive_set_and_inst(self):
         self._test_recursive_collection_and_inst(set)
 

Lib/test/test_dict.py

@@ -1825,6 +1825,15 @@ def __new__(self):
         self.assertEqual(type(fd), DictSubclass)
         self.assertEqual(created, frozendict(x=1))
 
+    def test_pickle(self):
+        for proto in range(2, pickle.HIGHEST_PROTOCOL + 1):
+            for fd in (
+                frozendict(),
+                frozendict(x=1, y=2),
+            ):
+                p = pickle.dumps(fd, proto)
+                self.assertEqual(fd, pickle.loads(p))
+
 
 if __name__ == "__main__":
     unittest.main()

Objects/dictobject.c

@@ -7930,6 +7930,18 @@ _PyObject_InlineValuesConsistencyCheck(PyObject *obj)
 
 // --- frozendict implementation ---------------------------------------------
 
+static PyObject *
+frozendict_getnewargs(PyObject *op, PyObject *Py_UNUSED(dummy))
+{
+    // Call dict(op): convert 'op' frozendict to a dict
+    PyObject *arg = PyObject_CallOneArg((PyObject*)&PyDict_Type, op);
+    if (arg == NULL) {
+        return NULL;
+    }
+    return Py_BuildValue("(N)", arg);
+}
+
+
 static PyNumberMethods frozendict_as_number = {
     .nb_or = frozendict_or,
 };
@@ -7951,6 +7963,7 @@ static PyMethodDef frozendict_methods[] = {
     DICT_COPY_METHODDEF
     DICT___REVERSED___METHODDEF
     {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
+    {"__getnewargs__", frozendict_getnewargs, METH_NOARGS},
     {NULL,              NULL}   /* sentinel */
 };