Implement Proper Name Mangling

When types have attributes starting with two underscores but
ending with at most one, Python uses name mangling to create
a unique private variable.

PySide needs to obey this rule in the tp_getattro methods.
We implemented it as an optimized _Pep_PrivateMangle function that
solves the problem internally without exposing the _Py_Mangle
function.

Remark: I think the exclusion of the _Py_Mangle function is another
oversight in the Limited API.

Task-number: PYSIDE-772
Change-Id: I0bfc2418dae439e963a16e37443f2099c6980696
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

2 files changed, 122 insertions, 0 deletions

diff --git a/sources/pyside2/tests/QtWidgets/CMakeLists.txt b/sources/pyside2/tests/QtWidgets/CMakeLists.txt
index 4bc17ebee..36f1ba80a 100644
--- a/sources/pyside2/tests/QtWidgets/CMakeLists.txt
+++ b/sources/pyside2/tests/QtWidgets/CMakeLists.txt
@@ -79,6 +79,7 @@ PYSIDE_TEST(keep_reference_test.py)
 PYSIDE_TEST(missing_symbols_test.py)
 PYSIDE_TEST(paint_event_test.py)
 PYSIDE_TEST(parent_method_test.py)
+PYSIDE_TEST(private_mangle_test.py)
 PYSIDE_TEST(python_properties_test.py)
 PYSIDE_TEST(qabstracttextdocumentlayout_test.py)
 PYSIDE_TEST(qaction_test.py)
diff --git a/sources/pyside2/tests/QtWidgets/private_mangle_test.py b/sources/pyside2/tests/QtWidgets/private_mangle_test.py
new file mode 100644
index 000000000..31a870691
--- /dev/null
+++ b/sources/pyside2/tests/QtWidgets/private_mangle_test.py
@@ -0,0 +1,121 @@
+#############################################################################
+##
+## 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.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+"""
+This is the example from https://bugreports.qt.io/browse/PYSIDE-772
+with no interaction as a unittest.
+"""
+
+import unittest
+from PySide2.QtCore import Signal
+from PySide2.QtWidgets import QApplication, QWidget
+from PySide2 import QtWidgets
+
+class Harness(QWidget):
+    clicked = Signal()
+
+    def __init__(self):
+        QWidget.__init__(self)
+        self.clicked.connect(self.method)
+        self.clicked.connect(self._method)
+        self.clicked.connect(self.__method)
+
+    def method(self):  # Public method
+        self.method_result = self.sender()
+
+    def _method(self):  # Private method
+        self.method__result = self.sender()
+
+    def __method(self):  # Name mangled method
+        self.method___result = self.sender()
+
+
+class _Under(QWidget):
+    clicked = Signal()
+
+    def __init__(self):
+        QWidget.__init__(self)
+        self.clicked.connect(self.method)
+        self.clicked.connect(self._method)
+        self.clicked.connect(self.__method)
+
+    def method(self):  # Public method
+        self.method_result = self.sender()
+
+    def _method(self):  # Private method
+        self.method__result = self.sender()
+
+    def __method(self):  # Name mangled method
+        self.method___result = self.sender()
+
+
+class TestMangle(unittest.TestCase):
+
+    def setUp(self):
+        QApplication()
+
+    def tearDown(self):
+        del QtWidgets.qApp
+
+    def testPrivateMangle(self):
+        harness = Harness()
+        harness.clicked.emit()
+        self.assertEqual(harness.method_result, harness)
+        self.assertEqual(harness.method__result, harness)
+        self.assertEqual(harness.method___result, harness)
+        self.assertTrue("method" in type(harness).__dict__)
+        self.assertTrue("_method" in type(harness).__dict__)
+        self.assertFalse("__method" in type(harness).__dict__)
+        self.assertTrue("_Harness__method" in type(harness).__dict__)
+
+    def testPrivateMangleUnder(self):
+        harness = _Under()
+        harness.clicked.emit()
+        self.assertEqual(harness.method_result, harness)
+        self.assertEqual(harness.method__result, harness)
+        self.assertEqual(harness.method___result, harness)
+        # make sure that we skipped over the underscore in "_Under"
+        self.assertTrue("method" in type(harness).__dict__)
+        self.assertTrue("_method" in type(harness).__dict__)
+        self.assertFalse("__method" in type(harness).__dict__)
+        self.assertTrue("_Under__method" in type(harness).__dict__)
+
+
+if __name__ == '__main__':
+    unittest.main()