Python 3.12: Fix the type generation intermediately

The type generation that we use all over the place does not work
any longer because Python 3.12.0a5 no longer allows meta classes with
a tp_new function.

The developers are aware of the omission and agree that a fix must
be found. After prior experience, this can take very long time.
To immediately continue, we implement a temporary patch that works.

Task-number: PYSIDE-2230
Change-Id: I8bf237411ca0e32e31ef4d3741a2def05f3e39f6
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
(cherry picked from commit ff40e74847cae1e746fc857597209294ca2c2568)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 32 insertions, 1 deletions

diff --git a/sources/shiboken6/libshiboken/sbktypefactory.cpp b/sources/shiboken6/libshiboken/sbktypefactory.cpp
index 0da1a8e23..88878f5eb 100644
--- a/sources/shiboken6/libshiboken/sbktypefactory.cpp
+++ b/sources/shiboken6/libshiboken/sbktypefactory.cpp
@@ -37,6 +37,37 @@ static PyObject *_PyType_FromSpecWithBases(PyType_Spec *, PyObject *);
 
 #endif // PYPY_VERSION
 
+// PYSIDE-2230: Temporary fix for Python 3.12.
+//              A tp_new is no longer allowed in a meta class.
+//              Hopefully, the Python devs will supply the missing support.
+// Note: Python 3.12 is the first version that grabs the metaclass from base classes.
+static PyObject *_PyType_FromSpecWithBasesHack(PyType_Spec *spec, PyObject *bases)
+{
+    PyTypeObject *keepMeta{};
+    newfunc keepNew{};
+
+    if (bases) {
+        Py_ssize_t n = PyTuple_GET_SIZE(bases);
+        for (auto idx = 0; idx < n; ++idx) {
+            PyTypeObject *base = reinterpret_cast<PyTypeObject *>(PyTuple_GET_ITEM(bases, idx));
+            PyTypeObject *meta = Py_TYPE(base);
+            if (meta->tp_new != PyType_Type.tp_new) {
+                // make sure there is no second meta class
+                assert(keepMeta == nullptr);
+                keepMeta = meta;
+                keepNew = meta->tp_new;
+                meta->tp_new = PyType_Type.tp_new;
+            }
+        }
+    }
+
+    auto *ret = _PyType_FromSpecWithBases(spec, bases);
+
+    if (keepMeta)
+        keepMeta->tp_new = keepNew;
+    return ret;
+}
+
 PyTypeObject *SbkType_FromSpec_BMDWB(PyType_Spec *spec,
                                      PyObject *bases,
                                      PyTypeObject *meta,
@@ -61,7 +92,7 @@ PyTypeObject *SbkType_FromSpec_BMDWB(PyType_Spec *spec,
     int package_level = atoi(spec->name);
     const char *mod = new_spec.name = colon + 1;
 
-    PyObject *obType = _PyType_FromSpecWithBases(&new_spec, bases);
+    PyObject *obType = _PyType_FromSpecWithBasesHack(&new_spec, bases);
     if (obType == nullptr)
         return nullptr;