Apply default values on update

python/core/qgsdefaultvalue.sip

@@ -72,11 +72,17 @@ class QgsDefaultValue
 
     bool isValid() const;
 %Docstring
- Returns if this default value is should be applied.
+ Returns if this default value should be applied.
  :return: false if the expression is a null string.
  :rtype: bool
 %End
 
+    operator bool() const;
+%Docstring
+ Checks if a default value is set. Alias for isValid().
+ :return: false if the expression is a null string.
+%End
+
 };
 
 /************************************************************************

python/core/qgsvectorlayer.sip

@@ -925,7 +925,7 @@ Return the provider type for this layer
     virtual bool addFeature( QgsFeature &feature, QgsFeatureSink::Flags flags = 0 );
 
 
-    bool updateFeature( QgsFeature &f );
+    bool updateFeature( const QgsFeature &f );
 %Docstring
  Updates an existing feature. This method needs to query the datasource
 on every call. Consider using changeAttributeValue() or
@@ -1172,13 +1172,13 @@ Returns list of attributes making up the primary key
  :rtype: bool
 %End
 
-    bool changeGeometry( QgsFeatureId fid, const QgsGeometry &geom );
+    bool changeGeometry( QgsFeatureId fid, const QgsGeometry &geom, bool skipDefaultValue = false );
 %Docstring
 Change feature's geometry
  :rtype: bool
 %End
 
-    bool changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue = QVariant() );
+    bool changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue = QVariant(), bool skipDefaultValues = false );
 %Docstring
  Changes an attribute value (but does not commit it)
 

src/core/qgsdefaultvalue.cpp

@@ -50,5 +50,10 @@ void QgsDefaultValue::setApplyOnUpdate( bool applyOnUpdate )
 
 bool QgsDefaultValue::isValid() const
 {
-  return mExpression.isEmpty();
+  return !mExpression.isEmpty();
+}
+
+QgsDefaultValue::operator bool() const
+{
+  return !mExpression.isEmpty();
 }

src/core/qgsdefaultvalue.h

@@ -84,11 +84,17 @@ class CORE_EXPORT QgsDefaultValue
     void setApplyOnUpdate( bool applyOnUpdate );
 
     /**
-     * Returns if this default value is should be applied.
+     * Returns if this default value should be applied.
      * \returns false if the expression is a null string.
      */
     bool isValid() const;
 
+    /**
+     * Checks if a default value is set. Alias for isValid().
+     * \returns false if the expression is a null string.
+     */
+    operator bool() const;
+
   private:
     QString mExpression;
     bool mApplyOnUpdate = false;

src/core/qgsvectorlayer.cpp

@@ -766,6 +766,25 @@ void QgsVectorLayer::setExtent( const QgsRectangle &r )
   mValidExtent = true;
 }
 
+void QgsVectorLayer::updateDefaultValues( QgsFeatureId fid, QgsFeature feature )
+{
+  if ( !mDefaultValueOnUpdateFields.isEmpty() )
+  {
+    if ( !feature.isValid() )
+      feature = getFeature( fid );
+
+    const QgsFields fields = mFields;
+    int size = fields.size();
+    for ( int idx : qgsAsConst( mDefaultValueOnUpdateFields ) )
+    {
+      if ( idx < 0 || idx >= size )
+        continue;
+
+      defaultValue( idx, feature );
+    }
+  }
+}
+
 QgsRectangle QgsVectorLayer::extent() const
 {
   QgsRectangle rect;
@@ -941,47 +960,52 @@ bool QgsVectorLayer::addFeature( QgsFeature &feature, Flags )
   return success;
 }
 
-bool QgsVectorLayer::updateFeature( QgsFeature &f )
+bool QgsVectorLayer::updateFeature( const QgsFeature &updatedFeature )
 {
-  QgsFeatureRequest req;
+  bool hasChanged = false;
-  req.setFilterFid( f.id() );
+  bool hasError = false;
-  if ( !f.hasGeometry() )
-    req.setFlags( QgsFeatureRequest::NoGeometry );
-  if ( f.attributes().isEmpty() )
-    req.setSubsetOfAttributes( QgsAttributeList() );
 
-  QgsFeature current;
+  QgsFeature currentFeature = getFeature( updatedFeature.id() );
-  if ( !getFeatures( req ).nextFeature( current ) )
+  if ( currentFeature.isValid() )
   {
-    QgsDebugMsg( QString( "feature %1 could not be retrieved" ).arg( f.id() ) );
+    QgsDebugMsg( QString( "feature %1 could not be retrieved" ).arg( updatedFeature.id() ) );
-    return false;
+
+    if ( updatedFeature.hasGeometry() && currentFeature.hasGeometry() && !updatedFeature.geometry().isGeosEqual( currentFeature.geometry() ) )
+    {
+      if ( changeGeometry( updatedFeature.id(), updatedFeature.geometry(), true ) )
+      {
+        hasChanged = true;
       }
-
+      else
-  if ( f.hasGeometry() && current.hasGeometry() && !f.geometry().isGeosEqual( current.geometry() ) )
       {
-    if ( !changeGeometry( f.id(), f.geometry() ) )
+        QgsDebugMsg( QString( "geometry of feature %1 could not be changed." ).arg( updatedFeature.id() ) );
-    {
-      QgsDebugMsg( QString( "geometry of feature %1 could not be changed." ).arg( f.id() ) );
-      return false;
       }
     }
 
-  QgsAttributes fa = f.attributes();
+    QgsAttributes fa = updatedFeature.attributes();
-  QgsAttributes ca = current.attributes();
+    QgsAttributes ca = currentFeature.attributes();
 
     for ( int attr = 0; attr < fa.count(); ++attr )
     {
       if ( fa.at( attr ) != ca.at( attr ) )
       {
-      if ( !changeAttributeValue( f.id(), attr, fa.at( attr ), ca.at( attr ) ) )
+        if ( changeAttributeValue( updatedFeature.id(), attr, fa.at( attr ), ca.at( attr ), true ) )
         {
-        QgsDebugMsg( QString( "attribute %1 of feature %2 could not be changed." ).arg( attr ).arg( f.id() ) );
+          hasChanged = true;
-        return false;
+        }
+        else
+        {
+          QgsDebugMsg( QString( "attribute %1 of feature %2 could not be changed." ).arg( attr ).arg( updatedFeature.id() ) );
+          hasError = true;
+        }
       }
     }
   }
 
-  return true;
+  if ( hasChanged && !mDefaultValueOnUpdateFields.isEmpty() )
+    updateDefaultValues( updatedFeature.id(), updatedFeature );
+
+  return !hasError;
 }
 
 
@@ -2260,7 +2284,7 @@ bool QgsVectorLayer::writeSld( QDomNode &node, QDomDocument &doc, QString &error
 }
 
 
-bool QgsVectorLayer::changeGeometry( QgsFeatureId fid, const QgsGeometry &geom )
+bool QgsVectorLayer::changeGeometry( QgsFeatureId fid, const QgsGeometry &geom, bool skipDefaultValue )
 {
   if ( !mEditBuffer || !mDataProvider )
   {
@@ -2272,33 +2296,40 @@ bool QgsVectorLayer::changeGeometry( QgsFeatureId fid, const QgsGeometry &geom )
   bool result = mEditBuffer->changeGeometry( fid, geom );
 
   if ( result )
+  {
     updateExtents();
+    if ( !skipDefaultValue && !mDefaultValueOnUpdateFields.isEmpty() )
+      updateDefaultValues( fid );
+  }
   return result;
 }
 
 
-bool QgsVectorLayer::changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue )
+bool QgsVectorLayer::changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue, bool skipDefaultValues )
 {
+  bool result = false;
+
   switch ( fields().fieldOrigin( field ) )
   {
     case QgsFields::OriginJoin:
-      return mJoinBuffer->changeAttributeValue( fid, field, newValue, oldValue );
+      result = mJoinBuffer->changeAttributeValue( fid, field, newValue, oldValue );
 
     case QgsFields::OriginProvider:
     case QgsFields::OriginEdit:
     case QgsFields::OriginExpression:
     {
-      if ( !mEditBuffer || !mDataProvider )
+      if ( mEditBuffer && mDataProvider )
-        return false;
+        result = mEditBuffer->changeAttributeValue( fid, field, newValue, oldValue );
-      else
-        return mEditBuffer->changeAttributeValue( fid, field, newValue, oldValue );
     }
 
     case QgsFields::OriginUnknown:
-      return false;
+      break;
   }
 
-  return false;
+  if ( result && !skipDefaultValues && !mDefaultValueOnUpdateFields.isEmpty() )
+    updateDefaultValues( fid );
+
+  return result;
 }
 
 bool QgsVectorLayer::addAttribute( const QgsField &field )
@@ -2920,6 +2951,9 @@ void QgsVectorLayer::updateFields()
 
     mFields[ index ].setAlias( aliasIt.value() );
   }
+
+  // Update default values
+  mDefaultValueOnUpdateFields.clear();
   QMap< QString, QgsDefaultValue >::const_iterator defaultIt = mDefaultExpressionMap.constBegin();
   for ( ; defaultIt != mDefaultExpressionMap.constEnd(); ++defaultIt )
   {
@@ -2928,6 +2962,8 @@ void QgsVectorLayer::updateFields()
       continue;
 
     mFields[ index ].setDefaultValue( defaultIt.value() );
+    if ( defaultIt.value().applyOnUpdate() )
+      mDefaultValueOnUpdateFields.insert( index );
   }
 
   QMap< QString, QgsFieldConstraints::Constraints >::const_iterator constraintIt = mFieldConstraints.constBegin();

src/core/qgsvectorlayer.h

@@ -913,7 +913,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
         \param f  Feature to update
         \returns   True in case of success and False in case of error
      */
-    bool updateFeature( QgsFeature &f );
+    bool updateFeature( const QgsFeature &f );
 
     /** Insert a new vertex before the given vertex number,
      *  in the given ring, item (first number is index 0), and feature
@@ -1142,7 +1142,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     bool setReadOnly( bool readonly = true );
 
     //! Change feature's geometry
-    bool changeGeometry( QgsFeatureId fid, const QgsGeometry &geom );
+    bool changeGeometry( QgsFeatureId fid, const QgsGeometry &geom, bool skipDefaultValue = false );
 
     /**
      * Changes an attribute value (but does not commit it)
@@ -1154,7 +1154,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      *
      * \returns true in case of success
      */
-    bool changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue = QVariant() );
+    bool changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue = QVariant(), bool skipDefaultValues = false );
 
     /** Add an attribute field (but does not commit it)
      * returns true if the field was added
@@ -1958,6 +1958,8 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
 
   private:                       // Private methods
 
+    void updateDefaultValues( QgsFeatureId fid, QgsFeature feature = QgsFeature() );
+
     /**
      * Returns true if the provider is in read-only mode
      */
@@ -2014,6 +2016,9 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     //! Map which stores default value expressions for fields
     QMap<QString, QgsDefaultValue> mDefaultExpressionMap;
 
+    //! An internal structure to keep track of fields that have a defaultValueOnUpdate
+    QSet<int> mDefaultValueOnUpdateFields;
+
     //! Map which stores constraints for fields
     QMap< QString, QgsFieldConstraints::Constraints > mFieldConstraints;