Python QML: serial port open signals "NoError" error

[lcongdon]

On first open, and on open after close, serial port signals a "PySide6.QtSerialPort.QSerialPort.SerialPortError.NoError" error. The application can read from and write to the port.

On second and subsequent opens, serial port signals "PySide6.QtSerialPort.QSerialPort.SerialPortError.OpenError" as expected.

On close when open, serial port signals nothing, as expected.

On close when closed, serial port signals "PySide6.QtSerialPort.QSerialPort.SerialPortError.NotOpenError" as expected.

Sample terminal application, which of course is C++ and is not QML, works as expected (full disclosure, trivially modified to use monospaced font).

Any recommendations, other than ignoring the error?

serial.py:

from PySide6.QtCore import Slot, QIODevice
from PySide6.QtQml import QmlElement
from PySide6.QtSerialPort import QSerialPort

QML_IMPORT_NAME = "Serial"
QML_IMPORT_MAJOR_VERSION = 1

@QmlElement
class Serial(QSerialPort):

    @Slot()
    def openSerialPort(self):
        self.setPortName("/dev/ttyACM0")
        self.open(QIODevice.ReadWrite)

    @Slot()
    def closeSerialPort(self):
        self.close()

    @Slot()
    def serialError(self):
        print(f"error: {self.error()}")

main.qml

import QtQuick
import QtQuick.Controls
import QtQuick.Layouts
import Serial

Window {
    id: window
    width: 200
    height: 200
    visible: true
    Serial {
        id: serial
        onErrorOccurred: {
            serial.serialError()
        }
    }
    ColumnLayout {
        Button {
            text: qsTr("Open Serial Port")
            onClicked: {
                console.log("Opening serial port")
                serial.openSerialPort()
            }
        }
        Button {
            text: qsTr("Close Serial Port")
            onClicked: {
                console.log("Closing serial port")
                serial.closeSerialPort()
            }
        }
    }
}

main.py

#!/usr/bin/python3
import sys
from pathlib import Path
import serial
from PySide6.QtGui import QGuiApplication
from PySide6.QtQml import QQmlApplicationEngine

if __name__ == "__main__":
    app = QGuiApplication(sys.argv)
    engine = QQmlApplicationEngine()
    qml_file = Path(__file__).resolve().parent / "main.qml"
    engine.load(qml_file)
    if not engine.rootObjects():
        sys.exit(-1)
    sys.exit(app.exec())