Data defined Assistant: closing the dialog without setting an expression invalidates the widget

[qgib]

Author Name: Harrissou Santanna (@DelazJ)
Original Redmine Issue: 16766
Affected QGIS version: 3.0.0
Redmine category:expressions

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I thought I had reported this issue but I couldn't find it in the tracker and given that it's still active...

Open a layer property dialog, Symbology tab
Select a parameter with a data-defined widget
Click the widget, choose Assistant... opening the DD configuration dialog
Close the new dialog without any change
The DD widget becomes red and is set with an errored expression.

I think that closing the dialog without any change shouldn't change DD widget expression.

Btw, hard to find the right category for this kind of issue

[qgib]

Author Name: Harrissou Santanna (@DelazJ)

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Things have been fixed when using the layer properties dialog but not in the styling panel

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• version was changed from master to 3.0.0

[roya0045]

This seems fixed. Can be closed.

[DelazJ]

I wouldn't say that: did you test in the styling panel, as mentioned above?
Here, the widget is no longer red but if you click on it, you'd notice that the "Assistant" entry is checked though no current expression associated. I don't know if this could potentially have side effect.... Also, if you had a field associated to the widget before you opened and undid the assistant panel, you get the same thing and lose the field association...

[roya0045]

@DelazJ Yes, in docked mode the widget is altered, see this

QGIS/src/gui/qgspropertyoverridebutton.cpp

Line 696 in 36ca201

if ( panel && panel->dockMode() )

And it directly linked to the legend. Yes there is no cancel button but you have undo, which act as cancel in this case. I would class this as solved. Maybe not perfect but solved.

[DelazJ]

Issue is that the user does not know that having opened that panel without any changes had "corrupted" his history, so he'll not probably undo anything (until he realiZes (how long after?) that his features do not display correctly (again with the assumption that an empty assistant corrupts anything - which I'm not able to investigate on)).

[Pedro-Murteira]

Can still replicate this issue on QGIS 3.16.14 and 3.22.1.

[alexbruy]

I don't think this is a bug. If you close assistant dialog without any changes then nothing happens. If you apply dialog, even without entering anything then checkbox is there no matter how you access symbology via layer properties or styling panel. And I think that in case of applying this is an expected behaviour as default configuation is also a valid configuration.

[github-actions]

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[DelazJ]

If you close assistant dialog without any changes then nothing happens.

Yes

If you apply dialog, even without entering anything then checkbox is there no matter how you access symbology via layer properties or styling panel.

maybe nitpicking but afaict you can not really apply that dialog in Layer styling panel so, not changing anything and moving back is like "Cancel", so the point above is applied in styling panel: nothing changes.
In Layer properties however (and unlike my previous comment), the "Assistant" checkbox is indeed checked now, and a "current" expression seems applied.

And I think that in case of applying this is an expected behaviour as default configuation is also a valid configuration.

Actually the applied expression, hence default configuration, is INVALID, as you can see if you press the "Edit" entry, because there is a missing parameter to construct a valid expression. Example for the Opacity parameter of a symbol coalesce(scale_linear(, 0, 0, 0, 100), 0)

IMHO, the Assistant dialog should have the same checks as some expression dialogs have and if the user did not select fields to have a valid expression, then the OK button remains greyed. Or we pre-filled the dialog (not my preference).

[alexbruy]

Can't reproduce with the latest master 79ccc22

[github-actions]

The QGIS project highly values your report and would love to see it addressed. However, this issue has been left in feedback mode for the last 14 days and is being automatically marked as "stale".
If you would like to continue with this issue, please provide any missing information or answer any open questions. If you could resolve the issue yourself meanwhile, please leave a note for future readers with the same problem and close the issue.
In case you should have any uncertainty, please leave a comment and we will be happy to help you proceed with this issue.
If there is no further activity on this issue, it will be closed in a week.

[github-actions]

While we hate to see this happen, this issue has been automatically closed because it has not had any activity in the last 42 days despite being marked as feedback. If this issue should be reconsidered, please follow the guidelines in the previous comment and reopen this issue.
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