pathlib: fix empty constructors in conversion

In some classes, like QDir, there is a default value
for constructors that accept a QString:

    QDir(const QString &path = QString())

However this case was not considered in Python land
when nothing is passed.
Considering other classes might have a similar situation,
we fix this at the level of the conversion and not per Qt class.

To reproduce this issue, a simple:

    from PySide6.QtCore import QDir
    a = QDir()

will segfault.

Added a simple test case,
and instructions to make the parameter optional (pyi).

Task-number: PYSIDE-1499
Change-Id: I42156b87ca0aa60466c743a8cc8b42ea5eeb3559
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 64 insertions, 0 deletions

diff --git a/sources/pyside6/tests/QtCore/qdir_test.py b/sources/pyside6/tests/QtCore/qdir_test.py
new file mode 100644
index 000000000..169959dbf
--- /dev/null
+++ b/sources/pyside6/tests/QtCore/qdir_test.py
@@ -0,0 +1,64 @@
+#############################################################################
+##
+## Copyright (C) 2021 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of the test suite of Qt for Python.
+##
+## $QT_BEGIN_LICENSE:GPL-EXCEPT$
+## 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 General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU
+## General Public License version 3 as published by the Free Software
+## Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+## 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-3.0.html.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+import os
+import sys
+import unittest
+
+from pathlib import Path
+sys.path.append(os.fspath(Path(__file__).resolve().parents[1]))
+from init_paths import init_test_paths
+init_test_paths(False)
+
+from PySide6.QtCore import QDir
+
+
+class QDirTest(unittest.TestCase):
+    '''Test case for QDir'''
+
+    def testConstructor(self):
+        # Optional case without arguments is equivalent to the constructor
+        #    QDir(const QString &path = QString())
+        a = QDir()
+
+        self.assertTrue(a.isReadable())
+        self.assertTrue(a.isRelative())
+
+        # Empty string
+        b = QDir("")
+        self.assertEqual(a, b)
+
+        # Empty Path
+        c = QDir(Path())
+        self.assertEqual(a, c)
+
+        self.assertEqual(b, c)
+
+
+if __name__ == '__main__':
+    unittest.main()