Remove Py_TPFLAGS_HAVE_VERSION_TAG in Python 3

The Py_TPFLAGS_DEFAULT in Python 3 has the
Py_TPFLAGS_HAVE_VERSION_TAG flag, which causes
the type attribute cache in _PyType_Lookup. According to
the Shiboken implementation for Python 2, this is not we expected.
So remove the Py_TPFLAGS_HAVE_VERSION_TAG flag from
Py_TPFLAGS_DEFAULT in Python 3.

Task-number: PYSIDE-60
Change-Id: Id731a59b65640eb5adea56fe06e0deb58ac4a168
Reviewed-by: Christian Tismer <tismer@stackless.com>

3 files changed, 72 insertions, 0 deletions

diff --git a/sources/pyside2/tests/QtCore/CMakeLists.txt b/sources/pyside2/tests/QtCore/CMakeLists.txt
index aba691838..649e796cc 100644
--- a/sources/pyside2/tests/QtCore/CMakeLists.txt
+++ b/sources/pyside2/tests/QtCore/CMakeLists.txt
@@ -1,3 +1,4 @@
+PYSIDE_TEST(attr_cache_py3k.py)
 PYSIDE_TEST(bug_278_test.py)
 PYSIDE_TEST(bug_332.py)
 PYSIDE_TEST(bug_408.py)
diff --git a/sources/pyside2/tests/QtCore/attr_cache_py3k.py b/sources/pyside2/tests/QtCore/attr_cache_py3k.py
new file mode 100644
index 000000000..ec0575b02
--- /dev/null
+++ b/sources/pyside2/tests/QtCore/attr_cache_py3k.py
@@ -0,0 +1,65 @@
+# This Python file uses the following encoding: utf-8
+
+#############################################################################
+##
+## Copyright (C) 2018 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of Qt for Python.
+##
+## $QT_BEGIN_LICENSE:LGPL$
+## Commercial License Usage
+## Licensees holding valid commercial Qt licenses may use this file in
+## accordance with the commercial license agreement provided with the
+## Software or, alternatively, in accordance with the terms contained in
+## a written agreement between you and The Qt Company. For licensing terms
+## and conditions see https://www.qt.io/terms-conditions. For further
+## information use the contact form at https://www.qt.io/contact-us.
+##
+## GNU Lesser General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU Lesser
+## General Public License version 3 as published by the Free Software
+## Foundation and appearing in the file LICENSE.LGPL3 included in the
+## packaging of this file. Please review the following information to
+## ensure the GNU Lesser General Public License version 3 requirements
+## will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+##
+## GNU General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU
+## General Public License version 2.0 or (at your option) the GNU General
+## Public license version 3 or any later version approved by the KDE Free
+## Qt Foundation. The licenses are as published by the Free Software
+## Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+## included in the packaging of this file. Please review the following
+## information to ensure the GNU General Public License requirements will
+## be met: https://www.gnu.org/licenses/gpl-2.0.html and
+## https://www.gnu.org/licenses/gpl-3.0.html.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+'''
+Unit tests for attribute cache in Python 3
+
+This is the original code from the bug report
+https://bugreports.qt.io/browse/PYSIDE-60
+'''
+
+from PySide2.QtCore import QObject
+
+
+class A(QObject):
+    instance = 1
+
+    @classmethod
+    def test(cls):
+        cls.instance
+        cls.instance = cls()
+        assert "<__main__.A object " in repr(cls.__dict__['instance'])
+        assert "<__main__.A object " in repr(cls.instance)
+        assert "<__main__.A object " in repr(type.__getattribute__(cls, 'instance'))
+
+
+if __name__ == "__main__":
+    A.test()
diff --git a/sources/shiboken2/libshiboken/sbkpython.h b/sources/shiboken2/libshiboken/sbkpython.h
index a26c318d1..fbac016eb 100644
--- a/sources/shiboken2/libshiboken/sbkpython.h
+++ b/sources/shiboken2/libshiboken/sbkpython.h
@@ -71,6 +71,12 @@
     #define PyInt_AsSsize_t(x)  PyLong_AsSsize_t(x)
     #define PyString_Type PyUnicode_Type
 
+    // In Python 3, Py_TPFLAGS_DEFAULT contains Py_TPFLAGS_HAVE_VERSION_TAG,
+    // which will trigger the attribute cache, which is not intended in Qt for Python.
+    // Use a customized Py_TPFLAGS_DEFAULT by defining Py_TPFLAGS_HAVE_VERSION_TAG = 0.
+    #undef Py_TPFLAGS_HAVE_VERSION_TAG
+    #define Py_TPFLAGS_HAVE_VERSION_TAG  (0)
+
 #else
     // Note: if there wasn't for the old-style classes, only a PyNumber_Check would suffice.
     #define SbkNumber_Check(X) \