From 2e939e0d454f09a8b003e385cc379b92bde50008 Mon Sep 17 00:00:00 2001
From: Alessandro Pasotti <elpaso@itopen.it>
Date: Fri, 14 Feb 2020 09:50:56 +0100
Subject: [PATCH] Merge pull request #34428 from
 elpaso/bugfix-gh34404-crash-on-apply-default-value

Fix crash when switching "apply default value on update"
---
 src/gui/qgsattributeform.cpp | 62 +++++++++++++++++++++---------------
 src/gui/qgsattributeform.h   |  2 ++
 2 files changed, 38 insertions(+), 26 deletions(-)

diff --git a/src/gui/qgsattributeform.cpp b/src/gui/qgsattributeform.cpp
index 96d94e4d369a..2edff59fd32e 100644
--- a/src/gui/qgsattributeform.cpp
+++ b/src/gui/qgsattributeform.cpp
@@ -446,6 +446,10 @@ bool QgsAttributeForm::saveEdits()
 
 bool QgsAttributeForm::updateDefaultValues( const int originIdx )
 {
+
+  // Synchronize
+  updateDefaultValueDependencies();
+
   if ( !mDefaultValueDependencies.contains( originIdx ) )
     return false;
 
@@ -1544,32 +1548,7 @@ void QgsAttributeForm::init()
     }
   }
 
-  //create defaultValueDependencies
-  for ( QgsWidgetWrapper *ww : qgis::as_const( mWidgets ) )
-  {
-    QgsEditorWidgetWrapper *eww = qobject_cast<QgsEditorWidgetWrapper *>( ww );
-    if ( eww )
-    {
-      QgsExpression exp( eww->field().defaultValueDefinition().expression() );
-      const QSet<QString> referencedColumns = exp.referencedColumns();
-      for ( const QString &referencedColumn : referencedColumns )
-      {
-        if ( referencedColumn == QgsFeatureRequest::ALL_ATTRIBUTES )
-        {
-          const QList<int> allAttributeIds( mLayer->fields().allAttributesList() );
-
-          for ( const int id : allAttributeIds )
-          {
-            mDefaultValueDependencies.insertMulti( id, eww );
-          }
-        }
-        else
-        {
-          mDefaultValueDependencies.insertMulti( mLayer->fields().lookupField( referencedColumn ), eww );
-        }
-      }
-    }
-  }
+  updateDefaultValueDependencies();
 
   if ( !mButtonBox )
   {
@@ -2401,6 +2380,37 @@ bool QgsAttributeForm::fieldIsEditable( int fieldIndex ) const
   return QgsVectorLayerUtils::fieldIsEditable( mLayer, fieldIndex, mFeature );
 }
 
+void QgsAttributeForm::updateDefaultValueDependencies()
+{
+  mDefaultValueDependencies.clear();
+  //create defaultValueDependencies
+  for ( QgsWidgetWrapper *ww : qgis::as_const( mWidgets ) )
+  {
+    QgsEditorWidgetWrapper *eww = qobject_cast<QgsEditorWidgetWrapper *>( ww );
+    if ( eww )
+    {
+      QgsExpression exp( eww->field().defaultValueDefinition().expression() );
+      const QSet<QString> referencedColumns = exp.referencedColumns();
+      for ( const QString &referencedColumn : referencedColumns )
+      {
+        if ( referencedColumn == QgsFeatureRequest::ALL_ATTRIBUTES )
+        {
+          const QList<int> allAttributeIds( mLayer->fields().allAttributesList() );
+
+          for ( const int id : allAttributeIds )
+          {
+            mDefaultValueDependencies.insertMulti( id, eww );
+          }
+        }
+        else
+        {
+          mDefaultValueDependencies.insertMulti( mLayer->fields().lookupField( referencedColumn ), eww );
+        }
+      }
+    }
+  }
+}
+
 void QgsAttributeForm::updateIcon( QgsEditorWidgetWrapper *eww )
 {
   if ( !eww->widget() || !mIconMap[eww->widget()] )
diff --git a/src/gui/qgsattributeform.h b/src/gui/qgsattributeform.h
index feb81215e5d5..3c8aa3220e59 100644
--- a/src/gui/qgsattributeform.h
+++ b/src/gui/qgsattributeform.h
@@ -325,6 +325,8 @@ class GUI_EXPORT QgsAttributeForm : public QWidget
 
     bool fieldIsEditable( const QgsVectorLayer &layer, int fieldIndex, QgsFeatureId fid ) const;
 
+    void updateDefaultValueDependencies();
+
     struct WidgetInfo
     {
       QWidget *widget = nullptr;