Attributes Form, Value relation broken

[stefan-overkamp]

Describe the bug

QGIS Attribute Forms with value relations show different values then in Identify result dialog and database.

How to Reproduce

project file and geopackage
https://geodaten.metropoleruhr.de/owncloud/s/N8S98l96zCFeIQL

1. Select Layer radwege
2. Activate feature identify tool and click on a feature
3. Open the features form
4. Compare the value of field Status (e.g. in Betrieb (use)) in identify result dialog and form
5. The form doesn't show correct values, value relations with 1:n configured show no matches
6. Setting the layer to edit mode shows correct values but closing and opening the form again shows false values again

QGIS and OS versions

QGIS-Version 3.18.0-Zürich QGIS-Codeversion bdef9fb
Kompiliert gegen Qt 5.15.2
Windows 10, Version 1909

There is no problem with value relations on:
QGIS-Version 3.16.4-Hannover QGIS-Codeversion 654e76b

[stefan-overkamp]

[roya0045]

@suricactus do you know if some of your changes might be related to this or could it be something else?

[elpaso]

This fixes the issue for me but I'd like to know what was changed to trigger this issue in the first place

diff --git a/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp b/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp
index df790af9fc..3fa2aa4a4d 100644
--- a/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp
+++ b/src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp
@@ -325,7 +325,7 @@ void QgsValueRelationWidgetWrapper::setFeature( const QgsFeature &feature )
     {
       if ( ! mCache.isEmpty() )
       {
-        updateValues( mCache.at( 0 ).key );
+        updateValues( formFeature().attribute( fieldIdx() ).isValid() ? formFeature().attribute( fieldIdx() ) : mCache.at( 0 ).key );
       }
     } );
   }