Fix chained filters and tests

src/gui/editorwidgets/qgsrelationreferencewidget.cpp

@@ -258,6 +258,22 @@ void QgsRelationReferenceWidget::setForeignKey( const QVariant &value )
   else
   {
     mComboBox->setIdentifierValue( value );
+
+    if ( mChainFilters )
+    {
+      QVariant nullValue = QgsApplication::nullRepresentation();
+
+      QgsFeatureRequest request = mComboBox->currentFeatureRequest();
+
+      mReferencedLayer->getFeatures( request ).nextFeature( mFeature );
+
+      for ( int i = 0; i < mFilterFields.size(); i++ )
+      {
+        QVariant v = mFeature.attribute( mFilterFields[i] );
+        QString f = v.isNull() ? nullValue.toString() : v.toString();
+        mFilterComboBoxes.at( i )->setCurrentIndex( mFilterComboBoxes.at( i )->findText( f ) );
+      }
+    }
   }
 
   mRemoveFKButton->setEnabled( mIsEditable );
@@ -292,6 +308,8 @@ void QgsRelationReferenceWidget::deleteForeignKey()
   else
   {
     mComboBox->setIdentifierValue( QVariant() );
+
+
   }
   mRemoveFKButton->setEnabled( false );
   updateAttributeEditorFrame( QgsFeature() );

tests/src/gui/testqgsrelationreferencewidget.cpp

@@ -25,6 +25,7 @@
 #include <qgsrelationmanager.h>
 #include <attributetable/qgsattributetablefiltermodel.h>
 #include "qgsfeaturelistcombobox.h"
+#include "qgsfeaturefiltermodel.h"
 #include "qgsgui.h"
 
 class TestQgsRelationReferenceWidget : public QObject
@@ -180,12 +181,17 @@ void TestQgsRelationReferenceWidget::testChainFilter()
   cbs[2]->setCurrentIndex( cbs[2]->findText( QStringLiteral( "brides" ) ) );
   cbs[1]->setCurrentIndex( cbs[1]->findText( QStringLiteral( "diameter" ) ) );
 
+  QEventLoop loop;
+  connect( qobject_cast<QgsFeatureFilterModel *>( w.mComboBox->model() ), &QgsFeatureFilterModel::filterJobCompleted, &loop, &QEventLoop::quit );
+  loop.exec();
+
   // combobox should propose NULL, 10 and 11 because the filter is now:
   // "material" == 'iron'
   QCOMPARE( w.mComboBox->count(), 3 );
 
   // if there's no filter at all, all features' id should be proposed
   cbs[0]->setCurrentIndex( cbs[0]->findText( QStringLiteral( "material" ) ) );
+  loop.exec();
   QCOMPARE( w.mComboBox->count(), 4 );
 }