gh-141510: Add PyFrozenDict_AsDict() function

* PyDict_Copy() no longer accepts frozendict.
* Remove _PyDict_CopyAsDict() function.
* Fix frozendict.items() ^ frozendict.items(). Add non-regression test.

Author: vstinner

Doc/c-api/dict.rst

@@ -82,10 +82,6 @@ Dictionary objects
 
    Return a new dictionary that contains the same key-value pairs as *p*.
 
-   .. versionchanged:: next
-      If *p* is a subclass of :class:`frozendict`, the result will be a
-      :class:`frozendict` instance instead of a :class:`dict` instance.
-
 .. c:function:: int PyDict_SetItem(PyObject *p, PyObject *key, PyObject *val)
 
    Insert *val* into the dictionary *p* with a key of *key*.  *key* must be
@@ -546,6 +542,10 @@ Frozen dictionary objects
 
    Create an empty dictionary if *iterable* is ``NULL``.
 
+.. c:function:: PyObject* PyFrozenDict_AsDict(PyObject *p)
+
+   Convert a :class:`frozendict` to a :class:`dict` (create a copy).
+
 
 Ordered dictionaries
 ^^^^^^^^^^^^^^^^^^^^

Include/cpython/dictobject.h

@@ -106,3 +106,6 @@ PyAPI_FUNC(int) PyDict_Unwatch(int watcher_id, PyObject* dict);
 
 // Create a frozendict. Create an empty dictionary if iterable is NULL.
 PyAPI_FUNC(PyObject*) PyFrozenDict_New(PyObject *iterable);
+
+// Convert a frozendict to a dict (create a copy).
+PyAPI_FUNC(PyObject*) PyFrozenDict_AsDict(PyObject *o);

Include/internal/pycore_dict.h

@@ -160,8 +160,6 @@ extern void _PyDict_Clear_LockHeld(PyObject *op);
 PyAPI_FUNC(void) _PyDict_EnsureSharedOnRead(PyDictObject *mp);
 #endif
 
-extern PyObject* _PyDict_CopyAsDict(PyObject *op);
-
 #define DKIX_EMPTY (-1)
 #define DKIX_DUMMY (-2)  /* Used internally */
 #define DKIX_ERROR (-3)

Lib/test/test_capi/test_dict.py

@@ -97,21 +97,13 @@ def test_dictproxy_new(self):
     def test_dict_copy(self):
         # Test PyDict_Copy()
         copy = _testlimitedcapi.dict_copy
-        for dict_type in ANYDICT_TYPES:
+        for dict_type in DICT_TYPES:
             dct = dict_type({1: 2})
             dct_copy = copy(dct)
-            if dict_type == frozendict:
-                expected_type = frozendict
-                self.assertIs(dct_copy, dct)
-            else:
-                if issubclass(dict_type, frozendict):
-                    expected_type = frozendict
-                else:
-                    expected_type = dict
-                self.assertIs(type(dct_copy), expected_type)
-                self.assertEqual(dct_copy, dct)
+            self.assertIs(type(dct_copy), dict)
+            self.assertEqual(dct_copy, dct)
 
-        for test_type in NOT_ANYDICT_TYPES + OTHER_TYPES:
+        for test_type in NOT_DICT_TYPES + OTHER_TYPES:
             self.assertRaises(SystemError, copy, test_type())
         self.assertRaises(SystemError, copy, NULL)
 
@@ -632,6 +624,19 @@ def test_frozendict_new(self):
         self.assertEqual(dct, frozendict())
         self.assertIs(type(dct), frozendict)
 
+    def test_frozendict_asdict(self):
+        # Test PyFrozenDict_AsDict()
+        frozendict_asdict = _testlimitedcapi.frozendict_asdict
+        for dict_type in FROZENDICT_TYPES:
+            dct = dict_type({1: 2})
+            dct_copy = frozendict_asdict(dct)
+            self.assertIs(type(dct_copy), dict)
+            self.assertEqual(dct_copy, dct)
+
+        for test_type in NOT_FROZENDICT_TYPES + OTHER_TYPES:
+            self.assertRaises(SystemError, frozendict_asdict, test_type())
+        self.assertRaises(SystemError, frozendict_asdict, NULL)
+
 
 if __name__ == "__main__":
     unittest.main()

Lib/test/test_dict.py

@@ -1848,11 +1848,19 @@ def test_merge(self):
                          frozendict({'x': 1, 'y': 2}))
         self.assertEqual(frozendict(x=1, y=2) | frozendict(y=5),
                          frozendict({'x': 1, 'y': 5}))
+        self.assertEqual(FrozenDict(x=1, y=2) | FrozenDict(y=5),
+                         frozendict({'x': 1, 'y': 5}))
+
         fd = frozendict(x=1, y=2)
         self.assertIs(fd | frozendict(), fd)
         self.assertIs(fd | {}, fd)
         self.assertIs(frozendict() | fd, fd)
 
+        fd = FrozenDict(x=1, y=2)
+        self.assertEqual(fd | frozendict(), fd)
+        self.assertEqual(fd | {}, fd)
+        self.assertEqual(frozendict() | fd, fd)
+
     def test_update(self):
         # test "a |= b" operator
         d = frozendict(x=1)
@@ -1863,6 +1871,11 @@ def test_update(self):
         self.assertEqual(d, frozendict({'x': 1, 'y': 2}))
         self.assertEqual(copy, frozendict({'x': 1}))
 
+    def test_items_xor(self):
+        # test "a ^ b" operator on items views
+        res = frozendict(a=1, b=2).items() ^ frozendict(b=2, c=3).items()
+        self.assertEqual(res, {('a', 1), ('c', 3)})
+
     def test_repr(self):
         d = frozendict()
         self.assertEqual(repr(d), "frozendict()")

Modules/_testcapi/dict.c

@@ -295,6 +295,14 @@ frozendict_new(PyObject *self, PyObject *obj)
 }
 
 
+static PyObject*
+frozendict_asdict(PyObject *self, PyObject *obj)
+{
+    NULLABLE(obj);
+    return PyFrozenDict_AsDict(obj);
+}
+
+
 static PyMethodDef test_methods[] = {
     {"dict_containsstring", dict_containsstring, METH_VARARGS},
     {"dict_getitemref", dict_getitemref, METH_VARARGS},
@@ -311,6 +319,7 @@ static PyMethodDef test_methods[] = {
     {"anydict_check", anydict_check, METH_O},
     {"anydict_checkexact", anydict_checkexact, METH_O},
     {"frozendict_new", frozendict_new, METH_O},
+    {"frozendict_asdict", frozendict_asdict, METH_O},
     {NULL},
 };
 

Objects/clinic/dictobject.c.h

@@ -146,8 +146,9 @@ static int dict_merge_from_seq2(PyObject *d, PyObject *seq2, int override);
 
 /*[clinic input]
 class dict "PyDictObject *" "&PyDict_Type"
+class frozendict "PyFrozenDictObject *" "&PyFrozenDict_Type"
 [clinic start generated code]*/
-/*[clinic end generated code: output=da39a3ee5e6b4b0d input=f157a5a0ce9589d6]*/
+/*[clinic end generated code: output=da39a3ee5e6b4b0d input=5dfa93bac68e7c54]*/
 
 
 /*
@@ -4384,7 +4385,23 @@ copy_lock_held(PyObject *o, int as_frozendict)
     return NULL;
 }
 
-// Similar to PyDict_Copy(), but copy also frozendict.
+PyObject *
+PyDict_Copy(PyObject *o)
+{
+    if (o == NULL || !PyDict_Check(o)) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+
+    PyObject *res;
+    Py_BEGIN_CRITICAL_SECTION(o);
+    res = copy_lock_held(o, 0);
+    Py_END_CRITICAL_SECTION();
+    return res;
+}
+
+// Similar to PyDict_Copy(), but return a frozendict if the argument
+// is a frozendict.
 static PyObject *
 _PyDict_Copy(PyObject *o)
 {
@@ -4397,27 +4414,14 @@ _PyDict_Copy(PyObject *o)
     return res;
 }
 
-PyObject *
-PyDict_Copy(PyObject *o)
+PyObject*
+PyFrozenDict_AsDict(PyObject *o)
 {
-    if (o == NULL || !PyAnyDict_Check(o)) {
+    if (o == NULL || !PyFrozenDict_Check(o)) {
         PyErr_BadInternalCall();
         return NULL;
     }
 
-    if (PyFrozenDict_CheckExact(o)) {
-        return Py_NewRef(o);
-    }
-
-    return _PyDict_Copy(o);
-}
-
-// Similar to PyDict_Copy(), but return a dict if the argument is a frozendict.
-PyObject*
-_PyDict_CopyAsDict(PyObject *o)
-{
-    assert(PyAnyDict_Check(o));
-
     PyObject *res;
     Py_BEGIN_CRITICAL_SECTION(o);
     res = copy_lock_held(o, 0);
@@ -6523,7 +6527,7 @@ dictitems_xor_lock_held(PyObject *d1, PyObject *d2)
     ASSERT_DICT_LOCKED(d1);
     ASSERT_DICT_LOCKED(d2);
 
-    PyObject *temp_dict = copy_lock_held(d1, PyFrozenDict_Check(d1));
+    PyObject *temp_dict = copy_lock_held(d1, 0);
     if (temp_dict == NULL) {
         return NULL;
     }
@@ -8057,7 +8061,7 @@ static PyMethodDef frozendict_methods[] = {
     DICT_ITEMS_METHODDEF
     DICT_VALUES_METHODDEF
     DICT_FROMKEYS_METHODDEF
-    DICT_COPY_METHODDEF
+    FROZENDICT_COPY_METHODDEF
     DICT___REVERSED___METHODDEF
     {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
     {"__getnewargs__", frozendict_getnewargs, METH_NOARGS},
@@ -8182,6 +8186,25 @@ PyFrozenDict_New(PyObject *iterable)
     }
 }
 
+/*[clinic input]
+frozendict.copy
+
+Return a shallow copy of the frozendict.
+[clinic start generated code]*/
+
+static PyObject *
+frozendict_copy_impl(PyFrozenDictObject *self)
+/*[clinic end generated code: output=e580fd91d9fc2cf7 input=35f6abeaa08fd4bc]*/
+{
+    assert(PyFrozenDict_Check(self));
+
+    if (PyFrozenDict_CheckExact(self)) {
+        return Py_NewRef(self);
+    }
+
+    return _PyDict_Copy((PyObject*)self);
+}
+
 
 PyTypeObject PyFrozenDict_Type = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)

Objects/dictobject.c

@@ -4850,7 +4850,13 @@ type_new_get_slots(type_new_ctx *ctx, PyObject *dict)
 static PyTypeObject*
 type_new_init(type_new_ctx *ctx)
 {
-    PyObject *dict = _PyDict_CopyAsDict(ctx->orig_dict);
+    PyObject *dict;
+    if (PyFrozenDict_Check(ctx->orig_dict)) {
+        dict = PyFrozenDict_AsDict(ctx->orig_dict);
+    }
+    else {
+        dict = PyDict_Copy(ctx->orig_dict);
+    }
     if (dict == NULL) {
         goto error;
     }