Implement default __ne__ and __eq__ for all PySide types

PySide types have been following the Qt implementation of
comparisons, completely.

This is not correct for Python, because the Python default has
the operators `==` and `!=` at least. They are needed for tests
like `obj in collection`.

We fix this by redirecting the default case to
`PyBaseObject_Type.tp_richcompare`.
This is the correct way to fix it, because for types which do not
define `tp_richcompare', this is the default, anyway.

From the original patch, the test case is still in use.

Old message:
Implement __ne__ and __eq__ for QTreeWidgetItem

Testing if a QTreeWidgetItem belongs to a list raises a NotImplementedError.
I have exposed the operator== and the operator!= from C++ to shiboken which has solved our eq operator issue.
Implemented the test from PYSIDE-74 for the QTreeWidgetItem eq operator and the ne operator.
This also allows us to have the behavior "QTreeWidgetItem in ['a']" and "QTreeWidgetItem not in ['a']".
Adding qtreewidgetitem_test.py to CMakeFiles.txt

Fixes: PYSIDE-74
Change-Id: Id221c0163fc8c2d85730c4c26f22db5f61710706
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

1 files changed, 14 insertions, 0 deletions

diff --git a/sources/pyside2/doc/considerations.rst b/sources/pyside2/doc/considerations.rst
index f05d929b5..b5eae7d86 100644
--- a/sources/pyside2/doc/considerations.rst
+++ b/sources/pyside2/doc/considerations.rst
@@ -133,3 +133,17 @@ Abandoned Alternative
 
 We also tried an alternative implementation with a ``qApp()`` function that was more *pythonic*
 and problem free, but many people liked the ``qApp`` macro better for its brevity, so here it is.
+
+
+Rich Comparison
+~~~~~~~~~~~~~~~
+
+There was a long-standing bug in the ``tp_richcompare`` implementation of PySide classes.
+
+* When a class did not implement it, the default implementation of ``object`` is used.
+  This implements ``==`` and ``!=`` like the ``is`` operator.
+
+* When a class implements only a single function like ``<``, then the default implementation
+  was disabled, and expressions like ``obj in sequence`` failed with ``NotImplemented``.
+
+This oversight was fixed in version 5.15.1 .