Fix drill-down in multi-edit mode

Fixes #40910

src/app/qgisapp.cpp

@@ -10078,12 +10078,13 @@ void QgisApp::modifyAttributesOfSelectedFeatures()
   }
 
   //dummy feature
-  QgsFeature f;
+  QgsFeature f( vl->fields() );
   QgsAttributeEditorContext context( createAttributeEditorContext() );
   context.setAllowCustomUi( false );
   context.setVectorLayerTools( mVectorLayerTools );
   context.setCadDockWidget( mAdvancedDigitizingDockWidget );
   context.setMapCanvas( mMapCanvas );
+  context.setAttributeFormMode( QgsAttributeEditorContext::Mode::MultiEditMode );
 
   QgsAttributeDialog *dialog = new QgsAttributeDialog( vl, &f, false, this, true, context );
   dialog->setMode( QgsAttributeEditorContext::MultiEditMode );

src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp

@@ -281,9 +281,18 @@ void QgsValueRelationWidgetWrapper::widgetValueChanged( const QString &attribute
       // If the value has changed as a result of another widget's value change,
       // we need to emit the signal to make sure other dependent widgets are
       // updated.
-      if ( oldValue != value() && fieldIdx() < formFeature().fields().count() )
+      QgsFields formFields( formFeature().fields() );
+
+      // Also check for fields in the layer in case this is a multi-edit form
+      // and there is not form feature set
+      if ( formFields.count() == 0 && layer() )
+      {
+        formFields = layer()->fields();
+      }
+
+      if ( oldValue != value() && fieldIdx() < formFields.count() )
       {
-        QString attributeName( formFeature().fields().names().at( fieldIdx() ) );
+        QString attributeName( formFields.names().at( fieldIdx() ) );
         setFormFeatureAttribute( attributeName, value( ) );
         emitValueChanged();
       }
@@ -305,7 +314,7 @@ void QgsValueRelationWidgetWrapper::setFeature( const QgsFeature &feature )
   // A bit of logic to set the default value if AllowNull is false and this is a new feature
   // Note that this needs to be here after the cache has been created/updated by populate()
   // and signals unblocked (we want this to propagate to the feature itself)
-  if ( formFeature().isValid()
+  if ( context().attributeFormMode() != QgsAttributeEditorContext::Mode::MultiEditMode
        && ! formFeature().attribute( fieldIdx() ).isValid()
        && ! mCache.isEmpty()
        && ! config( QStringLiteral( "AllowNull" ) ).toBool( ) )

src/gui/qgsattributeform.cpp

@@ -704,8 +704,8 @@ bool QgsAttributeForm::saveMultiEdits()
 
   bool success = true;
 
-  const auto constMMultiEditFeatureIds = mMultiEditFeatureIds;
-  for ( QgsFeatureId fid : constMMultiEditFeatureIds )
+  const auto constMultiEditFeatureIds = mMultiEditFeatureIds;
+  for ( QgsFeatureId fid : constMultiEditFeatureIds )
   {
     QgsAttributeMap::const_iterator aIt = newAttributeValues.constBegin();
     for ( ; aIt != newAttributeValues.constEnd(); ++aIt )
@@ -914,6 +914,8 @@ void QgsAttributeForm::onAttributeChanged( const QVariant &value, const QVariant
         mMultiEditUnsavedMessageBarItem = new QgsMessageBarItem( msgLabel, Qgis::Warning );
         if ( !mButtonBox->isVisible() )
           mMessageBar->pushItem( mMultiEditUnsavedMessageBarItem );
+
+        emit widgetValueChanged( eww->field().name(), value, !mIsSettingFeature );
       }
       break;
     }
@@ -1008,30 +1010,35 @@ void QgsAttributeForm::updateContainersVisibility()
 
 void QgsAttributeForm::updateConstraint( const QgsFeature &ft, QgsEditorWidgetWrapper *eww )
 {
-  QgsFieldConstraints::ConstraintOrigin constraintOrigin = mLayer->isEditable() ? QgsFieldConstraints::ConstraintOriginNotSet : QgsFieldConstraints::ConstraintOriginLayer;
 
-  if ( eww->layer()->fields().fieldOrigin( eww->fieldIdx() ) == QgsFields::OriginJoin )
+  if ( mContext.attributeFormMode() != QgsAttributeEditorContext::Mode::MultiEditMode )
   {
-    int srcFieldIdx;
-    const QgsVectorLayerJoinInfo *info = eww->layer()->joinBuffer()->joinForFieldIndex( eww->fieldIdx(), eww->layer()->fields(), srcFieldIdx );
 
-    if ( info && info->joinLayer() && info->isDynamicFormEnabled() )
+    QgsFieldConstraints::ConstraintOrigin constraintOrigin = mLayer->isEditable() ? QgsFieldConstraints::ConstraintOriginNotSet : QgsFieldConstraints::ConstraintOriginLayer;
+
+    if ( eww->layer()->fields().fieldOrigin( eww->fieldIdx() ) == QgsFields::OriginJoin )
     {
-      if ( mJoinedFeatures.contains( info ) )
-      {
-        eww->updateConstraint( info->joinLayer(), srcFieldIdx, mJoinedFeatures[info], constraintOrigin );
-        return;
-      }
-      else // if we are here, it means there's not joined field for this feature
+      int srcFieldIdx;
+      const QgsVectorLayerJoinInfo *info = eww->layer()->joinBuffer()->joinForFieldIndex( eww->fieldIdx(), eww->layer()->fields(), srcFieldIdx );
+
+      if ( info && info->joinLayer() && info->isDynamicFormEnabled() )
       {
-        eww->updateConstraint( QgsFeature() );
-        return;
+        if ( mJoinedFeatures.contains( info ) )
+        {
+          eww->updateConstraint( info->joinLayer(), srcFieldIdx, mJoinedFeatures[info], constraintOrigin );
+          return;
+        }
+        else // if we are here, it means there's not joined field for this feature
+        {
+          eww->updateConstraint( QgsFeature() );
+          return;
+        }
       }
     }
+    // default constraint update
+    eww->updateConstraint( ft, constraintOrigin );
   }
 
-  // default constraint update
-  eww->updateConstraint( ft, constraintOrigin );
 }
 
 void QgsAttributeForm::updateLabels()

src/gui/qgsattributeformeditorwidget.cpp

@@ -221,7 +221,8 @@ void QgsAttributeFormEditorWidget::setFieldTriggered()
 
 void QgsAttributeFormEditorWidget::onAggregateChanged()
 {
-  for ( QgsSearchWidgetWrapper *searchWidget : searchWidgetWrappers() )
+  const auto constWigets( searchWidgetWrappers() );
+  for ( QgsSearchWidgetWrapper *searchWidget : constWigets )
     searchWidget->setAggregate( mAggregateButton->aggregate() );
 }