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Details

Type: Bug
Resolution: Fixed
Priority: Not Evaluated
Fix Version/s: 6.8.0, 6.7.2
Affects Version/s: 6.7.0
Component/s: PySide
Labels:
None
Environment:
Python 3.12

Platform/s:

Windows
Commits:
36e2078d2 (dev), 060d38526 (6.7)

Description

When a function, queued by a zero-delay single-shot timer throws an exception, the exception is silently ignored but will cause other problems down the line.

This problem disappears by adding just 1ms delay to the timer.

See the following example:

from PySide6.QtCore import QTimer
from PySide6.QtWidgets import QApplication
from PySide6.QtWidgets import QPushButton
from PySide6.QtWidgets import QVBoxLayout
from PySide6.QtWidgets import QWidget

def fail():
    raise Exception("FAIL!")

app = QApplication()
b1 = QPushButton("FAIL now")
b1.clicked.connect(fail)
b2 = QPushButton("FAIL soon")
b2.clicked.connect(lambda: QTimer.singleShot(0, fail))
b3 = QPushButton("FAIL later")
b3.clicked.connect(lambda: QTimer.singleShot(1, fail))

widget = QWidget()
layout = QVBoxLayout(widget)
layout.addWidget(b1)
layout.addWidget(b2)
layout.addWidget(b3)

widget.show()
app.exec()

Clicking FAIL now or FAIL later will raise an exception as expected:

Traceback (most recent call last):
  File "c:\_WIP_\exceptions.py", line 8, in fail
    raise Exception("FAIL!")
Exception: FAIL!

Clicking FAIL soon once will not show any exception.

Clicking FAIL soon again will show the following traceback:

Traceback (most recent call last):
  File "c:\_WIP_\exceptions.py", line 8, in fail
    raise Exception("FAIL!")
Exception: FAIL!
c:\_WIP_\exceptions.py:14: RuntimeWarning: libshiboken: Overflow: Value 0 exceeds limits of type  [signed] "int" (4bytes).
  b2.clicked.connect(lambda: QTimer.singleShot(0, fail))
Traceback (most recent call last):
  File "c:\_WIP_\exceptions.py", line 14, in <lambda>
    b2.clicked.connect(lambda: QTimer.singleShot(0, fail))
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^
OverflowError

Clicking FAIL now or FAIL later after the first click on FAIL soon will show a different traceback.