libpyside6: Add a convenience function to convert a PyObject * to a QObject *

Task-number: PYSIDE-1709
Change-Id: I137d7fd3ac84f50bb6a799e27e07b7523d943812
Reviewed-by: Christian Tismer <tismer@stackless.com>
(cherry picked from commit a34622f8098d67c706148eac506460fc65a6401f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 40 insertions, 16 deletions

diff --git a/sources/pyside6/PySide6/QtQml/pysideqmlregistertype.cpp b/sources/pyside6/PySide6/QtQml/pysideqmlregistertype.cpp
index b769a1eb9..f7f1b2375 100644
--- a/sources/pyside6/PySide6/QtQml/pysideqmlregistertype.cpp
+++ b/sources/pyside6/PySide6/QtQml/pysideqmlregistertype.cpp
@@ -295,15 +295,10 @@ int PySide::qmlRegisterSingletonInstance(PyObject *pyObj, const char *uri, int v
     if (!isQObjectDerived(pyObjType, true))
         return -1;
 
-    // Check if the instance object derives from QObject
-    PyTypeObject *typeInstanceObject = instanceObject->ob_type;
-
-    if (!isQObjectDerived(typeInstanceObject, true))
-        return -1;
-
     // Convert the instanceObject (PyObject) into a QObject
-    QObject *instanceQObject = reinterpret_cast<QObject*>(
-            Object::cppPointer(reinterpret_cast<SbkObject*>(instanceObject), qObjectType()));
+    QObject *instanceQObject = PySide::convertToQObject(instanceObject, true);
+    if (instanceQObject == nullptr)
+        return -1;
 
     // Create Singleton Functor to pass the QObject to the Type registration step
     // similarly to the case when we have a callback
diff --git a/sources/pyside6/libpyside/pyside.cpp b/sources/pyside6/libpyside/pyside.cpp
index 5c3b0f3af..4769ea86d 100644
--- a/sources/pyside6/libpyside/pyside.cpp
+++ b/sources/pyside6/libpyside/pyside.cpp
@@ -649,18 +649,44 @@ bool registerInternalQtConf()
     return isRegistered;
 }
 
-bool isQObjectDerived(PyTypeObject *pyType, bool raiseError) {
-    static PyTypeObject *qobjectType = Shiboken::Conversions::getPythonTypeObject("QObject*");
+static PyTypeObject *qobjectType()
+{
+    static PyTypeObject * const result = Shiboken::Conversions::getPythonTypeObject("QObject*");
+    return result;
+}
 
-    if (!PyType_IsSubtype(pyType, qobjectType)) {
-        if (raiseError)
-            PyErr_Format(PyExc_TypeError, "A type inherited from %s expected, got %s.",
-                         qobjectType->tp_name, pyType->tp_name);
-        return false;
+bool isQObjectDerived(PyTypeObject *pyType, bool raiseError)
+{
+    const bool result = PyType_IsSubtype(pyType, qobjectType());
+    if (!result && raiseError) {
+        PyErr_Format(PyExc_TypeError, "A type inherited from %s expected, got %s.",
+                     qobjectType()->tp_name, pyType->tp_name);
     }
-    return true;
+    return result;
 }
 
+QObject *convertToQObject(PyObject *object, bool raiseError)
+{
+    if (object == nullptr) {
+        if (raiseError)
+            PyErr_Format(PyExc_TypeError, "None passed for QObject");
+        return nullptr;
+    }
+
+    if (!isQObjectDerived(Py_TYPE(object), raiseError))
+        return nullptr;
+
+    auto *sbkObject = reinterpret_cast<SbkObject*>(object);
+    auto *ptr = Shiboken::Object::cppPointer(sbkObject, qobjectType());
+    if (ptr == nullptr) {
+        if (raiseError) {
+            PyErr_Format(PyExc_TypeError, "Conversion of %s to QObject failed.",
+                         Py_TYPE(object)->tp_name);
+        }
+        return nullptr;
+    }
+    return reinterpret_cast<QObject*>(ptr);
+}
 
 } //namespace PySide
 
diff --git a/sources/pyside6/libpyside/pyside.h b/sources/pyside6/libpyside/pyside.h
index 3b1c85333..39fbef3cc 100644
--- a/sources/pyside6/libpyside/pyside.h
+++ b/sources/pyside6/libpyside/pyside.h
@@ -111,6 +111,9 @@ PYSIDE_API std::size_t getSizeOfQObject(PyTypeObject *type);
  */
 PYSIDE_API bool isQObjectDerived(PyTypeObject *pyType, bool raiseError);
 
+/// Convenience to convert a PyObject to QObject
+PYSIDE_API QObject *convertToQObject(PyObject *object, bool raiseError);
+
 typedef void (*CleanupFunction)(void);
 
 /**