[processing] Don't default to input field for optional expression par…

…ameters Fixes #41063
qgis · Jan 20, 2021 · 1fed902 · 1fed902
1 parent 5d14c61
commit 1fed902
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/src/gui/processing/qgsprocessingwidgetwrapperimpl.cpp b/src/gui/processing/qgsprocessingwidgetwrapperimpl.cpp
@@ -1951,6 +1951,9 @@ QWidget *QgsProcessingExpressionWidgetWrapper::createWidget()
           mFieldExpWidget->setToolTip( parameterDefinition()->toolTip() );
           mFieldExpWidget->setExpressionDialogTitle( parameterDefinition()->description() );
           mFieldExpWidget->registerExpressionContextGenerator( this );
+          if ( expParam->flags() & QgsProcessingParameterDefinition::FlagOptional )
+            mFieldExpWidget->setAllowEmptyFieldName( true );
+
           connect( mFieldExpWidget, static_cast < void ( QgsFieldExpressionWidget::* )( const QString & ) >( &QgsFieldExpressionWidget::fieldChanged ), this, [ = ]( const QString & )
           {
             emit widgetValueHasChanged( this );