[PyQt] Bug Report: pyqt5 discard silently signal with missing optional parameters (dataChanged roles for example)

[Phil Thompson]

On 10-01-2014 10:08 pm, Baptiste Lepilleur wrote:
> The issue is demonstrated in the attached example (pyqt 5.2, python
> 3.3). Below is the relevant excerpt:
>
> class ListModel(QAbstractItemModel):
>     def __init__(self, parent=None):
>         super(ListModel, self).__init__(parent)
>
>     def testEmit(self):
>         # This signal is silently dropped by pyqt (missing
> optional 3rd parameters). Why?
>         self.dataChanged.emit(self.createIndex(1,0),
> QModelIndex())
>         # This signal is sent as expected
>         self.dataChanged.emit(self.createIndex(2,0),
> QModelIndex(), [])
>
> * Bug description:
>
> The signal QAbstractItemModel::dataChanged has the following
> signature:
> void QAbstractItemModel::dataChanged(
>     const QModelIndex & topLeft, 
>     const QModelIndex & bottomRight, 
>     const QVector<int> & roles = QVector<int> ())
>
> If the optional roles parameters is not given when calling emit, the
> signal emission is discarded without any error reporting.
>
> For example:
>
>         self.dataChanged.emit(self.createIndex(1,0),
> QModelIndex())
>
> Below is the output of the attached example showing that the expected
> first emit "onDataChanged 1" is missing:
>
> C:Python33python.exe debugemit.py
>  onDataChanged 2
> ------------done-------------
>
> * Work-around:
>
> Pass the optional roles signal parameter:
>
>         self.dataChanged.emit(self.createIndex(2,0),
> QModelIndex(), [])
>
> * Remarks:
>
> This bug usually goes unseen because the views are usually
> automatically refreshed if the mouse if moved over the view 
> associated
> to the model.
>
> It was exposed by a model shared by multiple editable views with a
> custom setData(). It took many hours to figure out the root cause of
> the lack of refresh.
>
> IMHO a fairly serious bug as Ive never seen an example of
> dataChanged.emit() with the roles parameter...
>
> Lets me know if the above is unclear or more details are required, Id
> hate to see anyone else losing time on this issue,
> Baptiste.

This should be fixed in the current snapshots. The current SIP snapshot 
is required.

Phil