"RuntimeError: Failed to disconnect" with `PySide6==6.7.0`

[bersbersbers]

I recently tried upgrading to an early PySide6==6.7.0 (via https://download.qt.io/snapshots/ci/pyside/6.7/latest/pyside6), and I find that pytest then issues a lot of warnings that I cannot seem to suppress:

c:\Code\project.venv\Lib\site-packages\pytestqt\wait_signal.py:741: RuntimeError: Failed to disconnect (<bound method _AbstractSignalBlocker._quit_loop_by_timeout of <pytestqt.wait_signal.SignalBlocker object at 0x000001BE3BDA6390>>) from signal "timeout()".
signal.disconnect(slot)

filterwarnings = ["ignore"] does not seem to have an effect, possibly because RuntimeError is not a proper warning.

[nicoddemus]

It is probably because the exception is being raised inside the Qt event loop.

[penguinpee]

I'm seeing the same here:

=================================== FAILURES ===================================
________________________________ test_destroyed ________________________________
CALL ERROR: Exceptions caught in Qt event loop:
________________________________________________________________________________
RuntimeError: Internal C++ object (Obj) already deleted.
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "/builddir/build/BUILDROOT/python-pytest-qt-4.4.0-2.fc41.x86_64/usr/lib/python3.12/site-packages/pytestqt/wait_signal.py", line 219, in _quit_loop_by_signal
    self._cleanup()
  File "/builddir/build/BUILDROOT/python-pytest-qt-4.4.0-2.fc41.x86_64/usr/lib/python3.12/site-packages/pytestqt/wait_signal.py", line 226, in _cleanup
    _silent_disconnect(signal, self._quit_loop_by_signal)
  File "/builddir/build/BUILDROOT/python-pytest-qt-4.4.0-2.fc41.x86_64/usr/lib/python3.12/site-packages/pytestqt/wait_signal.py", line 741, in _silent_disconnect
    signal.disconnect(slot)
SystemError: <class 'RuntimeError'> returned a result with an exception set
________________________________________________________________________________
----------------------------- Captured stderr call -----------------------------
Exceptions caught in Qt event loop:
________________________________________________________________________________
RuntimeError: Internal C++ object (Obj) already deleted.
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "/builddir/build/BUILDROOT/python-pytest-qt-4.4.0-2.fc41.x86_64/usr/lib/python3.12/site-packages/pytestqt/wait_signal.py", line 219, in _quit_loop_by_signal
    self._cleanup()
  File "/builddir/build/BUILDROOT/python-pytest-qt-4.4.0-2.fc41.x86_64/usr/lib/python3.12/site-packages/pytestqt/wait_signal.py", line 226, in _cleanup
    _silent_disconnect(signal, self._quit_loop_by_signal)
  File "/builddir/build/BUILDROOT/python-pytest-qt-4.4.0-2.fc41.x86_64/usr/lib/python3.12/site-packages/pytestqt/wait_signal.py", line 741, in _silent_disconnect
    signal.disconnect(slot)
SystemError: <class 'RuntimeError'> returned a result with an exception set
________________________________________________________________________________

That test succeeded with PySide 6.6.2.

[nicoddemus]

A SystemError usually means a problem with the C code (in this case the C++ bindings).

Perhaps it would be good create a MWE and post this to PySide's tracker.

[bersbersbers]

Well, one MWE (without pytest-qt) is this:

from PySide6.QtCore import Signal
from PySide6.QtWidgets import QApplication, QMainWindow


class Window(QMainWindow):
    signal = Signal()

    def __init__(self):
        super().__init__()
        self.signal.connect(self.Slot)
        self.signal.disconnect(self.Slot)
        self.signal.disconnect(self.Slot)

    def Slot(self): ...

app = QApplication()
window = Window()
print("Done.")

But I somehow feel reporting this to PySide will give us the question "why are you disconnecting twice"? :)

I think the comment in line 738 is relevant here - is that what you have in mind?

pytest-qt/src/pytestqt/wait_signal.py

Lines 736 to 743 in aac9be7

	def _silent_disconnect(signal, slot):
	"""Disconnects a signal from a slot, ignoring errors. Sometimes
	Qt might disconnect a signal automatically for unknown reasons.
	"""
	try:
	signal.disconnect(slot)
	except (TypeError, RuntimeError): # pragma: no cover
	pass

I don't suppose you remember which code example made you do 86e41e3 :)

[bersbersbers]

Okay, here's a real one:

from PySide6.QtWidgets import QWidget

def test_disconnect(qtbot):
    widget = QWidget()
    qtbot.addWidget(widget)
    _ = qtbot.waitSignal(widget.windowTitleChanged, timeout=10000)
    widget.windowTitleChanged.emit("")

> pytest bug.py

======================================================================================= test session starts ======================================================================================== 
platform win32 -- Python 3.12.3, pytest-8.1.1, pluggy-1.5.0
PySide6 6.7.0 -- Qt runtime 6.7.0 -- Qt compiled 6.7.0
rootdir: C:\Code\project
plugins: qt-4.4.0
collected 1 item                                                                                                                                                                                     

bug.py .                                                                                                                                                                                      [100%] 

========================================================================================= warnings summary ========================================================================================= 
bug.py::test_disconnect
  c:\Code\project\.venv\Lib\site-packages\pytestqt\wait_signal.py:741: RuntimeError: Failed to disconnect (<bound method _AbstractSignalBlocker._quit_loop_by_timeout of <pytestqt.wait_signal.SignalBlocker object at 0x00000265849F0B60>>) from signal "timeout()".
    signal.disconnect(slot)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
=================================================================================== 1 passed, 1 warning in 0.10s =================================================================================== 

[bersbersbers]

And a workaround:

from PySide6.QtWidgets import QWidget

def test_disconnect(qtbot):
    widget = QWidget()
    qtbot.addWidget(widget)
    _ = qtbot.waitSignal(widget.windowTitleChanged, timeout=1)
    del _
    widget.windowTitleChanged.emit("")

Edit: yes, that fixes the issue in my big app.

Edit: another workaround is just to not assign to _ in the first place.

@nicoddemus, do you think this is reportable to PySide in this form, or will they want to see something without pytest-qt? Signal disconnect behaviors have been subject of bug fixing for the last 10 or so releases...

[nicoddemus]

@bersbersbers sorry for the delay.

The problem is:

1. pytest-qt does the right thing and ignores the runtime error in case it is disconnected twice. In our case it is OK because the signal might have been disconnected by the user at that point.
2. PySide is emitting a warning that somehow is bypassing the standard warnings filter, that's why using filterwarnings in pytest has no effect.

Here is a MWE which shows the problem, without using pytest-qt:

import warnings
from PySide6.QtCore import Signal
from PySide6.QtWidgets import QApplication, QMainWindow


warnings.filterwarnings('ignore')

class Window(QMainWindow):
    signal = Signal()

    def __init__(self):
        super().__init__()
        self.signal.connect(self.Slot)
        self.signal.disconnect(self.Slot)
        self.signal.disconnect(self.Slot)

    def Slot(self): ...

warnings.warn(Warning("some warning"))
app = QApplication()
window = Window()
print("Done")

While we should see no warnings at all due to warnings.filterwarnings, this prints:

e:\projects\pytest-qt\tests\foo.py:15: RuntimeError: Failed to disconnect (<bound method Window.Slot of <__main__.Window(0x2220ac06c40) at 0x000002220CF995C0>>) from signal "signal()".
  self.signal.disconnect(self.Slot)
Done

As a sanity check, if we comment out warnings.filterwarnings, we see both warnings as expected:

e:\projects\pytest-qt\tests\foo.py:19: Warning: some warning
  warnings.warn(Warning("some warning"))
e:\projects\pytest-qt\tests\foo.py:15: RuntimeError: Failed to disconnect (<bound method Window.Slot of <__main__.Window(0x28947215dd0) at 0x0000028949219680>>) from signal "signal()".
  self.signal.disconnect(self.Slot)
Done

[bersbersbers]

@nicoddemus thanks - and no worries about the delay. I have found a workaround for my issue, and will work on getting this solved only as a bonus for others, so I have no strict timeline here. In summary, I see two issues:

• "RuntimeError: Failed to disconnect" with PySide6==6.7.0 #552 (comment) shows an non-pytest-qt MWE that generates a non-suppressable warning when disconnecting a signal twice.
• "RuntimeError: Failed to disconnect" with PySide6==6.7.0 #552 (comment) shows a (still pytest-qt-based) MWE that shows how PySide behaves differently depending on whether qtbot.waitSignal is assigned an output variable or not.

I will report both issues to PySide and updates this thread here.

[nicoddemus]

Thanks!

I will close for now, but looking forward to the follow ups. 👍

[bersbersbers]

Follow https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2705 if interested.

[nicoddemus]

Thanks! Watching that issue. 👍

[bersbersbers]

(Hopefully) fixed with PySide6 6.7.1 and 6.8.0.

[bersbersbers]

I tested this on an early 6.7.1 (pip install https://download.qt.io/snapshots/ci/pyside/6.7/latest/pyside6/shiboken6-6.7.0a1.dev1714496642-cp39-abi3-win_amd64.whl https://download.qt.io/snapshots/ci/pyside/6.7/latest/pyside6/PySide6_Essentials-6.7.0a1.dev1714496642-cp39-abi3-win_amd64.whl) and it is working fine. We are still getting the warning, but it can be suppressed now. Maybe you want to extend your try ... except block to ignore just that particular warning.