QAction::setData always emits dataChanged()

QAction::setData hasn't check that this data has allready set.

Look at code. I comment lines which can be added.

void
QAction::setData(const QVariant &data)
{
    Q_D(QAction);

//  if (d->userData == data)
//      return;

    d->userData = data;
    d->sendDataChanged();
}

Or documentation should explain that dataChanged() will always emit.

At this moment I doubt current behaviour is feature or bug. In my personal case I use this trick to force emit dataChanged when I want it and do not change any data in QAction object.