__feature__: Fix snake_case handling on user defined classes

The snake case feature filters candidate methods and turns
them into snake case. This works fine for built-in classes.
The assumption is that all methods come from the tp_methods
list.

This assumption is not correct when applied to user defined
classes. The methods have no static source in this case.
To distinguish here, we inspect the tp_methods list. If it
is empty, we assume a user defined class and do nothing.

A forgotten initialization in feature.py was added, too.

As a note: RHEL has such an old Python version that does
not have MethodDescriptorType in the types module.

[ChangeLog][PySide6] snake_case handling now does explicitly
not touch user defined classes.

Fixes: PYSIDE-1702
Change-Id: Idfa16cdc50cb7234c1d2f473dfae3a568887547e
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
(cherry picked from commit 42695262f0ab4c73377b9d638dd28636ab1a3668)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 47 insertions, 6 deletions

diff --git a/sources/pyside6/libpyside/feature_select.cpp b/sources/pyside6/libpyside/feature_select.cpp
index c82cccce1..9459e1ca9 100644
--- a/sources/pyside6/libpyside/feature_select.cpp
+++ b/sources/pyside6/libpyside/feature_select.cpp
@@ -499,10 +499,17 @@ static PyObject *methodWithNewName(PyTypeObject *type,
 
 static bool feature_01_addLowerNames(PyTypeObject *type, PyObject *prev_dict, int id)
 {
+    PyMethodDef *meth = type->tp_methods;
+    PyObject *lower_dict = type->tp_dict;
+
+    // PYSIDE-1702: A user-defined class in Python has no internal method list.
+    //              We are not going to change anything.
+    if (!meth)
+        return PyDict_Update(lower_dict, prev_dict) >= 0;
+
     /*
      * Add objects with lower names to `type->tp_dict` from 'prev_dict`.
      */
-    PyObject *lower_dict = type->tp_dict;
     PyObject *key, *value;
     Py_ssize_t pos = 0;
 
@@ -515,11 +522,9 @@ static bool feature_01_addLowerNames(PyTypeObject *type, PyObject *prev_dict, in
             continue;
         }
     }
+
     // Then we walk over the tp_methods to get all methods and insert
     // them with changed names.
-    PyMethodDef *meth = type->tp_methods;
-    if (!meth)
-        return true;
 
     for (; meth != nullptr && meth->ml_name != nullptr; ++meth) {
         const char *name = String::toCString(String::getSnakeCaseName(meth->ml_name, true));
@@ -648,11 +653,18 @@ static bool feature_02_true_property(PyTypeObject *type, PyObject *prev_dict, in
      * Use the property info to create true Python property objects.
      */
 
-    // The empty `tp_dict` gets populated by the previous dict.
+    PyMethodDef *meth = type->tp_methods;
     PyObject *prop_dict = type->tp_dict;
+
+    // The empty `tp_dict` gets populated by the previous dict.
     if (PyDict_Update(prop_dict, prev_dict) < 0)
         return false;
 
+    // PYSIDE-1702: A user-defined class in Python has no internal method list.
+    //              We are not going to change anything.
+    if (!meth)
+        return true;
+
     // For speed, we establish a helper dict that maps the removed property
     // method names to property name.
     PyObject *prop_methods = PyDict_GetItem(prop_dict, PyMagicName::property_methods());
diff --git a/sources/pyside6/tests/QtCore/snake_prop_feature_test.py b/sources/pyside6/tests/QtCore/snake_prop_feature_test.py
index 7925c4c0c..18a5e4058 100644
--- a/sources/pyside6/tests/QtCore/snake_prop_feature_test.py
+++ b/sources/pyside6/tests/QtCore/snake_prop_feature_test.py
@@ -67,7 +67,7 @@ class Window(QWidget):
 class FeatureTest(unittest.TestCase):
     def setUp(self):
         qApp or QApplication()
-        __feature__.set_selection(0)
+        __feature__.set_selection(0x80)     # FIXME: 0 is insecure
 
     def tearDown(self):
         __feature__.set_selection(0)
@@ -122,6 +122,34 @@ class FeatureTest(unittest.TestCase):
         self.assertEqual(qApp.quit_on_last_window_closed,
                          QApplication.quit_on_last_window_closed)
 
+    def testUserClassNotAffected(self):
+        FunctionType = type(lambda: 42)
+        # Note: the types module does not have MethodDescriptorType in low versions.
+        MethodDescriptorType = type(str.split)
+
+        class UserClass(QWidget):
+
+            def someFunc1(self):
+                pass
+
+            @staticmethod
+            def someFunc2(a, b):
+                pass
+
+        inspect = UserClass.__dict__
+        self.assertTrue(isinstance(inspect["someFunc1"], FunctionType))
+        self.assertTrue(isinstance(inspect["someFunc2"], staticmethod))
+        self.assertTrue(isinstance(UserClass.someFunc2, FunctionType))
+        self.assertTrue(isinstance(UserClass.addAction, MethodDescriptorType))
+
+        from __feature__ import snake_case
+
+        inspect = UserClass.__dict__
+        self.assertTrue(isinstance(inspect["someFunc1"], FunctionType))
+        self.assertTrue(isinstance(inspect["someFunc2"], staticmethod))
+        self.assertTrue(isinstance(UserClass.someFunc2, FunctionType))
+        self.assertTrue(isinstance(UserClass.add_action, MethodDescriptorType))
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/feature.py b/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/feature.py
index 8776c7de9..a2b3699cf 100644
--- a/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/feature.py
+++ b/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/feature.py
@@ -159,6 +159,7 @@ def __init__():
         # Initialize all prior imported modules
         for name in sys.modules:
             pyside_feature_dict.setdefault(name, -1)
+        _is_initialized = True
 
 
 def set_selection(select_id, mod_name=None):