feature-select: Implement a selectable feature framework

This is the framework for selectable features.
There are no real features implemented.

Planned is a maximum of 8 features.
They are all implemented as a dummy for now.

The decision depends of the following setting at the beginning of
a module after PySide2 import:

    from __feature__ import <feature name>

For more info, see the Jira issue, section

    The Principle Of Selectable Features In PySide

Task-number: PYSIDE-1019
Change-Id: If355e9294b5c16090b39d30422a90ea9c8523390
Reviewed-by: Christian Tismer <tismer@stackless.com>

2 files changed, 106 insertions, 0 deletions

diff --git a/sources/pyside2/tests/QtCore/CMakeLists.txt b/sources/pyside2/tests/QtCore/CMakeLists.txt
index 7973a51ca..771e1aeef 100644
--- a/sources/pyside2/tests/QtCore/CMakeLists.txt
+++ b/sources/pyside2/tests/QtCore/CMakeLists.txt
@@ -37,6 +37,7 @@ PYSIDE_TEST(deletelater_test.py)
 PYSIDE_TEST(destroysignal_test.py)
 PYSIDE_TEST(duck_punching_test.py)
 PYSIDE_TEST(emoji_string_test.py)
+PYSIDE_TEST(feature_test.py)
 PYSIDE_TEST(hash_test.py)
 PYSIDE_TEST(inherits_test.py)
 PYSIDE_TEST(max_signals.py)
diff --git a/sources/pyside2/tests/QtCore/feature_test.py b/sources/pyside2/tests/QtCore/feature_test.py
new file mode 100644
index 000000000..cf1e8c3f2
--- /dev/null
+++ b/sources/pyside2/tests/QtCore/feature_test.py
@@ -0,0 +1,105 @@
+#############################################################################
+##
+## Copyright (C) 2020 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.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+import os
+import sys
+import unittest
+
+sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+from init_paths import init_test_paths
+init_test_paths(False)
+
+from PySide2 import QtCore
+from PySide2.support.__feature__ import _really_all_feature_names
+from textwrap import dedent
+
+"""
+feature_test.py
+--------------
+
+This tests the selectable features in PySide.
+
+There are no real features implemented. They will be added, later.
+"""
+
+class FeaturesTest(unittest.TestCase):
+
+    def testAllFeatureCombinations(self):
+        """
+        Test for all 256 possible combinations of `__feature__` imports.
+        """
+        global __name__
+
+        for bit in range(8):
+            # We are cheating here, since the functions are in the globals.
+            exec(dedent("""
+
+        def tst_bit{0}(flag, self):
+            if flag == 0:
+                with self.assertRaises(AttributeError):
+                    QtCore.QCborArray.fake_feature_{1:02x}
+                with self.assertRaises(KeyError):
+                    QtCore.QCborArray.__dict__["fake_feature_{1:02x}"]
+            else:
+                QtCore.QCborArray.fake_feature_{1:02x}
+                QtCore.QCborArray.__dict__["fake_feature_{1:02x}"]
+
+                        """.format(bit, 1 << bit)), globals(), globals())
+        feature_list = _really_all_feature_names
+        func_list = [tst_bit0, tst_bit1, tst_bit2, tst_bit3,
+                     tst_bit4, tst_bit5, tst_bit6, tst_bit7]
+
+        for idx in range(0x100):
+            __name__ = "feature_{:02x}".format(idx)
+            print()
+            print("--- Feature Test Module `{}` ---".format(__name__))
+            print("Imports:")
+            for bit in range(8):
+                if idx & 1 << bit:
+                    feature = feature_list[bit]
+                    text = "from __feature__ import {}".format(feature)
+                    print(text)
+                    exec(text)
+            for bit in range(8):
+                value = idx & 1 << bit
+                func_list[bit](value, self=self)
+
+
+if __name__ == '__main__':
+    unittest.main()