Port virtual fields to expression contexts

Author: nyalldawson

src/core/qgsvectorlayerfeatureiterator.cpp

@@ -22,9 +22,11 @@
 #include "qgsvectorlayereditbuffer.h"
 #include "qgsvectorlayer.h"
 #include "qgsvectorlayerjoinbuffer.h"
+#include "qgsexpressioncontext.h"
 
 QgsVectorLayerFeatureSource::QgsVectorLayerFeatureSource( QgsVectorLayer *layer )
 {
+  mLayer = layer;
   mProviderFeatureSource = layer->dataProvider()->featureSource();
   mFields = layer->fields();
   mJoinBuffer = layer->mJoinBuffer->clone();
@@ -502,6 +504,11 @@ void QgsVectorLayerFeatureIterator::prepareExpressions()
 {
   const QList<QgsExpressionFieldBuffer::ExpressionField> exps = mSource->mExpressionFieldBuffer->expressions();
 
+  mExpressionContext.reset( new QgsExpressionContext() );
+  mExpressionContext->appendScope( QgsExpressionContextUtils::globalScope() );
+  mExpressionContext->appendScope( QgsExpressionContextUtils::projectScope() );
+  mExpressionContext->setFields( mSource->mFields );
+
   for ( int i = 0; i < mSource->mFields.count(); i++ )
   {
     if ( mSource->mFields.fieldOrigin( i ) == QgsFields::OriginExpression )
@@ -512,7 +519,7 @@ void QgsVectorLayerFeatureIterator::prepareExpressions()
       {
         int oi = mSource->mFields.fieldOriginIndex( i );
         QgsExpression* exp = new QgsExpression( exps[oi].expression );
-        exp->prepare( mSource->mFields );
+        exp->prepare( mExpressionContext.data() );
         mExpressionFieldInfo.insert( i, exp );
 
         if ( mRequest.flags() & QgsFeatureRequest::SubsetOfAttributes )
@@ -572,7 +579,8 @@ void QgsVectorLayerFeatureIterator::addVirtualAttributes( QgsFeature& f )
     for ( ; it != mExpressionFieldInfo.constEnd(); ++it )
     {
       QgsExpression* exp = it.value();
-      QVariant val = exp->evaluate( f );
+      mExpressionContext->setFeature( f );
+      QVariant val = exp->evaluate( mExpressionContext.data() );
       mSource->mFields.at( it.key() ).convertCompatible( val );;
       f.setAttribute( it.key(), val );
     }

src/core/qgsvectorlayerfeatureiterator.h

@@ -26,6 +26,7 @@ class QgsVectorLayer;
 class QgsVectorLayerEditBuffer;
 class QgsVectorLayerJoinBuffer;
 struct QgsVectorJoinInfo;
+class QgsExpressionContext;
 
 class QgsVectorLayerFeatureIterator;
 
@@ -42,6 +43,8 @@ class QgsVectorLayerFeatureSource : public QgsAbstractFeatureSource
 
   protected:
 
+    QgsVectorLayer* mLayer;
+
     QgsAbstractFeatureSource* mProviderFeatureSource;
 
     QgsVectorLayerJoinBuffer* mJoinBuffer;
@@ -158,6 +161,8 @@ class CORE_EXPORT QgsVectorLayerFeatureIterator : public QgsAbstractFeatureItera
     //! optional object to locally simplify edited (changed or added) geometries fetched by this feature iterator
     QgsAbstractGeometrySimplifier* mEditGeometrySimplifier;
 
+    QScopedPointer<QgsExpressionContext> mExpressionContext;
+
     //! returns whether the iterator supports simplify geometries on provider side
     virtual bool providerCanSimplify( QgsSimplifyMethod::MethodType methodType ) const override;
 };