DoubleSpinBox.valueChanged fires without the value having changed when setting maximum to NaN

Setting the maximum of a QDoubleSpinBox to NaN sets its value to NaN. This is not documented, but it is not documented that it does not do that, so I can kind of accept it.

However, when doing so repeatedly, QDoubleSpinBox.valueChanged fires repeatedly although the value has not changed.

I created a Python-based example at https://bugreports.qt.io/browse/PYSIDE-2126. Unfortunately, I do not have a Qt-C++ dev environment installed, so I have not way of translating it. but I guess it is easy enough to read in Python code, the gist being:

QApplication()
box = QDoubleSpinBox()
box.valueChanged.connect(lambda: print("This should print only once."))
box.setMaximum(math.nan) # this calls value_changed, as expected (I guess)
box.setMaximum(math.nan) # this calls value_changed, certainly unexpected!

I would expect the second call to setMaximum to not fire anything, as the maximum hasn't changed and the value hasn't changed.