Fix aggregate expression calculation when used with virtual fields

The layer expression context (which is required for aggregate calculation to work) was not being added to the context used by vector layer feature iterators. Fix #15930
qgis · Jul 14, 2017 · 3f4d6de · 3f4d6de
1 parent 0639264
commit 3f4d6de
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Showing 4 changed files with 28 additions and 1 deletion.
diff --git a/python/core/qgsvectorlayerfeatureiterator.sip b/python/core/qgsvectorlayerfeatureiterator.sip
@@ -61,6 +61,7 @@ class QgsVectorLayerFeatureSource : QgsAbstractFeatureSource
 
 
 
+
 };
 
 

diff --git a/src/core/qgsvectorlayerfeatureiterator.cpp b/src/core/qgsvectorlayerfeatureiterator.cpp
@@ -79,6 +79,9 @@ QgsVectorLayerFeatureSource::QgsVectorLayerFeatureSource( const QgsVectorLayer *
     }
 #endif
   }
+
+  std::unique_ptr< QgsExpressionContextScope > layerScope( QgsExpressionContextUtils::layerScope( layer ) );
+  mLayerScope = *layerScope;
 }
 
 QgsVectorLayerFeatureSource::~QgsVectorLayerFeatureSource()
@@ -644,7 +647,7 @@ void QgsVectorLayerFeatureIterator::prepareFields()
   mExpressionContext.reset( new QgsExpressionContext() );
   mExpressionContext->appendScope( QgsExpressionContextUtils::globalScope() );
   mExpressionContext->appendScope( QgsExpressionContextUtils::projectScope( QgsProject::instance() ) );
-  mExpressionContext->setFields( mSource->mFields );
+  mExpressionContext->appendScope( new QgsExpressionContextScope( mSource->mLayerScope ) );
 
   mFieldsToPrepare = ( mRequest.flags() & QgsFeatureRequest::SubsetOfAttributes ) ? mRequest.subsetOfAttributes() : mSource->mFields.allAttributesList();
 

diff --git a/src/core/qgsvectorlayerfeatureiterator.h b/src/core/qgsvectorlayerfeatureiterator.h
@@ -84,6 +84,8 @@ class CORE_EXPORT QgsVectorLayerFeatureSource : public QgsAbstractFeatureSource
 
     QgsFields mFields;
 
+    QgsExpressionContextScope mLayerScope;
+
     bool mHasEditBuffer;
 
     // A deep-copy is only performed, if the original maps change

diff --git a/tests/src/python/test_qgsvectorlayer.py b/tests/src/python/test_qgsvectorlayer.py
@@ -1829,6 +1829,27 @@ def testAggregate(self):
         self.assertTrue(ok)
         self.assertEqual(val, 'this is a test')
 
+    def testAggregateInVirtualField(self):
+        """
+        Test aggregates in a virtual field
+        """
+        layer = QgsVectorLayer("Point?field=fldint:integer", "layer", "memory")
+        pr = layer.dataProvider()
+
+        int_values = [4, 2, 3, 2, 5, None, 8]
+        features = []
+        for i in int_values:
+            f = QgsFeature()
+            f.setFields(layer.fields())
+            f.setAttributes([i])
+            features.append(f)
+        assert pr.addFeatures(features)
+
+        field = QgsField('virtual', QVariant.Double)
+        layer.addExpressionField('sum(fldint*2)', field)
+        vals = [f['virtual'] for f in layer.getFeatures()]
+        self.assertEqual(vals, [48, 48, 48, 48, 48, 48, 48])
+
     def onLayerOpacityChanged(self, tr):
         self.opacityTest = tr