gh-60074: add new stable API function PyType_FromMetaclass (GH-93012)

Added a new stable API function ``PyType_FromMetaclass``, which mirrors
the behavior of ``PyType_FromModuleAndSpec`` except that it takes an
additional metaclass argument. This is, e.g., useful for language
binding tools that need to store additional information in the type
object.

1 files changed, 73 insertions, 0 deletions

diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 3bc7761..37f4ded 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -308,6 +308,32 @@ test_dict_inner(int count)
     }
 }
 
+static PyObject *pytype_fromspec_meta(PyObject* self, PyObject *meta)
+{
+    if (!PyType_Check(meta)) {
+        PyErr_SetString(
+            TestError,
+            "pytype_fromspec_meta: must be invoked with a type argument!");
+        return NULL;
+    }
+
+    PyType_Slot HeapCTypeViaMetaclass_slots[] = {
+        {0},
+    };
+
+    PyType_Spec HeapCTypeViaMetaclass_spec = {
+        "_testcapi.HeapCTypeViaMetaclass",
+        sizeof(PyObject),
+        0,
+        Py_TPFLAGS_DEFAULT,
+        HeapCTypeViaMetaclass_slots
+    };
+
+    return PyType_FromMetaclass(
+        (PyTypeObject *) meta, NULL, &HeapCTypeViaMetaclass_spec, NULL);
+}
+
+
 static PyObject*
 test_dict_iteration(PyObject* self, PyObject *Py_UNUSED(ignored))
 {
@@ -5886,6 +5912,7 @@ static PyMethodDef TestMethods[] = {
     {"test_long_numbits",       test_long_numbits,               METH_NOARGS},
     {"test_k_code",             test_k_code,                     METH_NOARGS},
     {"test_empty_argparse",     test_empty_argparse,             METH_NOARGS},
+    {"pytype_fromspec_meta",    pytype_fromspec_meta,            METH_O},
     {"parse_tuple_and_keywords", parse_tuple_and_keywords, METH_VARARGS},
     {"pyobject_repr_from_null", pyobject_repr_from_null, METH_NOARGS},
     {"pyobject_str_from_null",  pyobject_str_from_null, METH_NOARGS},
@@ -7078,6 +7105,38 @@ static PyType_Spec HeapCTypeSubclassWithFinalizer_spec = {
     HeapCTypeSubclassWithFinalizer_slots
 };
 
+static PyType_Slot HeapCTypeMetaclass_slots[] = {
+    {0},
+};
+
+static PyType_Spec HeapCTypeMetaclass_spec = {
+    "_testcapi.HeapCTypeMetaclass",
+    sizeof(PyHeapTypeObject),
+    sizeof(PyMemberDef),
+    Py_TPFLAGS_DEFAULT,
+    HeapCTypeMetaclass_slots
+};
+
+static PyObject *
+heap_ctype_metaclass_custom_tp_new(PyTypeObject *tp, PyObject *args, PyObject *kwargs)
+{
+    return PyType_Type.tp_new(tp, args, kwargs);
+}
+
+static PyType_Slot HeapCTypeMetaclassCustomNew_slots[] = {
+    { Py_tp_new, heap_ctype_metaclass_custom_tp_new },
+    {0},
+};
+
+static PyType_Spec HeapCTypeMetaclassCustomNew_spec = {
+    "_testcapi.HeapCTypeMetaclassCustomNew",
+    sizeof(PyHeapTypeObject),
+    sizeof(PyMemberDef),
+    Py_TPFLAGS_DEFAULT,
+    HeapCTypeMetaclassCustomNew_slots
+};
+
+
 typedef struct {
     PyObject_HEAD
     PyObject *dict;
@@ -7591,6 +7650,20 @@ PyInit__testcapi(void)
     Py_DECREF(subclass_with_finalizer_bases);
     PyModule_AddObject(m, "HeapCTypeSubclassWithFinalizer", HeapCTypeSubclassWithFinalizer);
 
+    PyObject *HeapCTypeMetaclass = PyType_FromMetaclass(
+        &PyType_Type, m, &HeapCTypeMetaclass_spec, (PyObject *) &PyType_Type);
+    if (HeapCTypeMetaclass == NULL) {
+        return NULL;
+    }
+    PyModule_AddObject(m, "HeapCTypeMetaclass", HeapCTypeMetaclass);
+
+    PyObject *HeapCTypeMetaclassCustomNew = PyType_FromMetaclass(
+        &PyType_Type, m, &HeapCTypeMetaclassCustomNew_spec, (PyObject *) &PyType_Type);
+    if (HeapCTypeMetaclassCustomNew == NULL) {
+        return NULL;
+    }
+    PyModule_AddObject(m, "HeapCTypeMetaclassCustomNew", HeapCTypeMetaclassCustomNew);
+
     if (PyType_Ready(&ContainerNoGC_type) < 0) {
         return NULL;
     }