Debug In-dialog provided python code in QGIS attribute form 'Python Init Code Configuration'

Question

In a QGIS layers attribute form configuration I have the following Python Init Code Configuration:

Code in plain text:

# -*- coding: utf-8 -*-

from qgis.PyQt.QtWidgets import QWidget, QLineEdit
from qgis.PyQt.QtCore import Qt

def atlas_punkte_init_values(dialog, layer, feature):
    #geom = feature.geometry()
    control = dialog.findChild(QLineEdit, 'str')
    print(control)
    l = dialog.findChildren(QLabel)
    print(l)

As one can see at first sight, this code is erroneous, because QLabel is not imported. By means of this, I would expect an exception somewhat like ...NameError: name 'QLabel' is not defined, but the only thing I get is this:

Because far trickier error constellations are imaginable than a forgotten import, debugging of more extensive scripts is nearly impossible that way.

First idea is to look at python errors in the log or the python console, but thats a fail.

Do I miss a location where qualified exceptions are thrown by these scripts or is there really no chance to properly debug these?

Answer 1

You should allow macros to run in "Settings > General". QGIS cannot find the function because macros is not allowed. In this case, QGIS shows an error message dialog and gives a warning in Log Messages panel in later versions as in the image.

When using 'Python Init Code Configuration', debugging is a black hole in earlier QGIS 3 versions. But in QGIS v3.12+, "Python error" window shows the error message now.