Implement Embedding To Make Signatures Always Available

Situation..

PySide works fine with normal applications. But when installers
are used to pack the application together, then the signature
extension cannot be loaded.

This is a problem that exists since the signature extension was
written. But starting with PySide 5.12.1, the signature extension
is very visible, because it is used to support the __doc__ attribute.

There have beed successful attempts to solve the problem for
PyInstaller and Py2App. But there are more packers available,
and they all need a change both in PySide and in the packer.

Solution..

To solve this problem once and for all, we embed the Python
support files in the binary shiboken package. When the Python
files are not normally accessible, they are unpacked from a ZIP
file.

Details..

- The embedded files shall only be used when the normal files
  are not available,

- The signature extension should no longer be lazily loaded.
  When the application starts, all files should be present.

- We drop support for shiboken2.support.signature and
  use a single, independen folder 'shibokensupport' (proposal).
  This avoids problems with multiple existence of the shiboken2
  folder. PySide2.support.signature remains the official interface,
  but it's only an alias when PySide2 exists.

- The embedding is used when the normal files cannot be
  loaded for some reason. It can be enforced by a sys variable
  "pyside_uses_embedding".

- Testcase is included.

- Tested with PyInstaller on macOS

Fixes: PYSIDE-932
Fixes: PYSIDE-942
Change-Id: Iaa62dc0623503a2e0943eedd10d2b2484c65cc2d
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 74 insertions, 0 deletions

diff --git a/sources/pyside2/tests/pysidetest/embedding_test.py b/sources/pyside2/tests/pysidetest/embedding_test.py
new file mode 100644
index 000000000..aa71360ca
--- /dev/null
+++ b/sources/pyside2/tests/pysidetest/embedding_test.py
@@ -0,0 +1,74 @@
+#############################################################################
+##
+## Copyright (C) 2019 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of PySide2.
+##
+## $QT_BEGIN_LICENSE:LGPL$
+## 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 unittest
+
+# This test tests the embedding feature of PySide.
+# Normally, embedding is only used when necessary.
+# By setting the variable "pyside_uses_embedding",
+# we enforce usage of embedding.
+
+
+class EmbeddingTest(unittest.TestCase):
+
+    # def test_pyside_normal(self):
+    #     import sys
+    #     self.assertFalse(hasattr(sys, "pyside_uses_embedding"))
+    #     import PySide2
+    #     # everything has to be imported
+    #     self.assertTrue("PySide2.support.signature" in sys.modules)
+    #     # there should be a variale in sys, now (no idea if set)
+    #     self.assertTrue(hasattr(sys, "pyside_uses_embedding"))
+
+    # Unfortunately, I see no way how to shut things enough down
+    # to trigger a second initiatization. Therefore, only one test :-/
+    def test_pyside_embedding(self):
+        import sys, os
+        self.assertFalse(hasattr(sys, "pyside_uses_embedding"))
+        sys.pyside_uses_embedding = "anything true"
+        import PySide2
+        # everything has to be imported
+        self.assertTrue("PySide2.support.signature" in sys.modules)
+        self.assertEqual(sys.pyside_uses_embedding, True)
+        dn = os.path.dirname
+        name = os.path.basename(dn(dn(dn(PySide2.support.signature.__file__))))
+        self.assertTrue(name.startswith("embedded.") and name.endswith(".zip"))
+
+if __name__ == '__main__':
+    unittest.main()