[PyQt] Overriding slots in mixins in PyQt5

[Phil Thompson]

On 25 Oct 2018, at 2:31 pm, Julio César Gázquez <julio_lists at mebamutual.com.ar> wrote:
> 
> Hi Phil and everybody.
> 
> I'm migrating our largest PyQt4 codebase to PyQt5. The process has been pretty uneventful until now, when I found this.
> 
> I have code with the following structure. Running it in PyQt4 I got the original, expected behavior, and clicking the button triggers the overriden slot. However in PyQt5 the base slot is triggered.
> 
> --- snip ---
> 
> import sys
> #from PyQt4.QtCore import pyqtSlot, QMetaObject
> #from PyQt4.QtGui import QApplication, QWidget, QPushButton, QMessageBox
> from PyQt5.QtCore import pyqtSlot, QMetaObject
> from PyQt5.QtWidgets import QApplication, QWidget, QPushButton, QMessageBox
> 
> 
> class BaseMixin:
> 
>     @pyqtSlot()
>     def on_button_clicked(self):
>         QMessageBox.information(self, 'Base Widget', 'Base slot')
> 
> 
> class OverridenMixin(BaseMixin):
> 
>     @pyqtSlot()
>     def on_button_clicked(self):
>         QMessageBox.information(self, 'Overriden Widget', 'Overriden slot')
>     
> 
> class Widget(QWidget, OverridenMixin):
>     
>     def __init__(self, parent=None):
>         super().__init__(parent)
>         self.button = QPushButton("Push me", self)
>         self.button.setObjectName("button")
>         self.button.show()
>         QMetaObject.connectSlotsByName(self)
>              
>     
> class App(QApplication):
> 
>     def __init__(self, argv):
>         super().__init__(argv)
>         self._widget = Widget()
>         self._widget.show()
> 
> 
> app = App(sys.argv)
> 
> app.exec_()
> 
> 
> --- snip ---
> 
> It got weirder as if I remove the decorators, the overriden slot is triggered, (yet I'd like to keep using the decorators in order to avoid getting triggered twice without dealing with the signal's checked parameter).
> I'm not sure if I'm doing something subtly wrong, or just using a completely unsupported way of doing things, and therefore utterly wrong. 
> 
> What should I do to get it working correctly, besides removing the decorators?
> 
> BTW, I'd like to keep the code working in PyQt4 for a while, but I'm afraid this is twisted enough to put extra constraints.

It's a bug that will be fixed in the next snapshot (which won't be tonight).

Thanks,
Phil