QtAsyncIO conflict with QDialog.exec()

dayongxie

When I use QtAsyncIO， I meet this problem，the code：

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations

from PySide6.QtCore import Qt
from PySide6.QtWidgets import (QApplication, QLabel, QMainWindow, QPushButton, QVBoxLayout, QWidget, QMessageBox)

import PySide6.QtAsyncio as QtAsyncio

import asyncio
import sys


class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()

        widget = QWidget()
        self.setCentralWidget(widget)

        layout = QVBoxLayout(widget)

        self.text = QLabel("The answer is 42.")
        layout.addWidget(self.text, alignment=Qt.AlignmentFlag.AlignCenter)

        async_trigger = QPushButton(text="What is the question?")
        async_trigger.clicked.connect(lambda: asyncio.ensure_future(self.set_text()))
        layout.addWidget(async_trigger, alignment=Qt.AlignmentFlag.AlignCenter)

    async def set_text(self):
        await asyncio.sleep(1)
        asyncio.ensure_future(self.set_text_2())
        # Dialog().exec() 
        QMessageBox.information(self, "Info", "This is an async message box.")
        self.text.setText("What do you get if you multiply six by nine?")

    async def set_text_2(self):
        await asyncio.sleep(1)
        print("hello world")


if __name__ == "__main__":
    app = QApplication(sys.argv)
    main_window = MainWindow()
    main_window.show()

    QtAsyncio.run(handle_sigint=True)

Create a new async task without await，then call QMessageBox.information() or QDialog.exec()
below exception will occur:

Traceback (most recent call last):
File "E:\test.venv\lib\site-packages\PySide6\QtAsyncio\events.py", line 571, in <lambda>
self._schedule_event(self._timeout, lambda: self._cb())
File "E:\test.venv\lib\site-packages\PySide6\QtAsyncio\events.py", line 579, in _cb
self._callback(*self._args)
File "E:\test.venv\lib\site-packages\PySide6\QtAsyncio\tasks.py", line 98, in _step
asyncio._leave_task(self._loop, self) # type: ignore[arg-type]
RuntimeError: Leaving task Task 'QtTask' with state: Done with exception (RuntimeError("Cannot enter into task Task 'QtTask' with state: Pending while another task Task 'QtTask' with state: Pending is being executed.")) does not match the current task Task 'QtTask' with state: Pending.

SGaist

Hi and welcome to devnet,

I haven't used that module yet however I think that manually triggering a secondary event loop like that is wrong.

I just found this example which confirms my intuition.