[Expression] Do not transform NULL integer as 0 when concat

Fixes #36112 : don't concat null values
qgis · May 18, 2020 · 01563e6 · 01563e6
1 parent dc8b8e9
commit 01563e6
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diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
@@ -1923,7 +1923,8 @@ static QVariant fcnConcat( const QVariantList &values, const QgsExpressionContex
   QString concat;
   for ( const QVariant &value : values )
   {
-    concat += QgsExpressionUtils::getStringValue( value, parent );
+    if ( !value.isNull() )
+      concat += QgsExpressionUtils::getStringValue( value, parent );
   }
   return concat;
 }

diff --git a/tests/src/core/testqgsexpression.cpp b/tests/src/core/testqgsexpression.cpp
@@ -3891,6 +3891,31 @@ class TestQgsExpression: public QObject
       QCOMPARE( QgsExpression::replaceExpressionText( input, &context ), expected );
     }
 
+    void testConcatNULLAttributeValue()
+    {
+      // Test that null integer values coming from provider are not transformed as 0
+      // https://github.com/qgis/QGIS/issues/36112
+
+      QgsFields fields;
+      fields.append( QgsField( QStringLiteral( "foo" ), QVariant::Int ) );
+
+      QgsFeature f;
+      f.initAttributes( 1 );
+      f.setAttribute( 0, QVariant( QVariant::Int ) );
+
+      QgsExpressionContext context = QgsExpressionContextUtils::createFeatureBasedContext( f, fields );
+      QgsExpression exp( QStringLiteral( "concat('test', foo)" ) );
+      QVariant res = exp.evaluate( &context );
+      QCOMPARE( res.type(), QVariant::String );
+      QCOMPARE( res.toString(), QStringLiteral( "test" ) );
+
+      f.setAttribute( 0, QVariant() );
+      context = QgsExpressionContextUtils::createFeatureBasedContext( f, fields );
+      res = exp.evaluate( &context );
+      QCOMPARE( res.type(), QVariant::String );
+      QCOMPARE( res.toString(), QStringLiteral( "test" ) );
+    }
+
 };
 
 QGSTEST_MAIN( TestQgsExpression )