Quote fields in size/width assistant (fix #14257)

python/gui/qgsfieldexpressionwidget.sip

@@ -46,6 +46,13 @@ class QgsFieldExpressionWidget : QWidget
       */
     QString currentText() const;
 
+    /** Returns the currently selected field or expression. If a field is currently selected, the returned
+     * value will be converted to a valid expression referencing this field (ie enclosing the field name with
+     * appropriate quotations).
+     * @note added in QGIS 2.14
+     */
+    QString asExpression() const;
+
     //! Returns the currently used layer
     QgsVectorLayer* layer() const;
 

src/gui/qgsfieldexpressionwidget.cpp

@@ -103,6 +103,11 @@ QString QgsFieldExpressionWidget::currentText() const
   return mCombo->currentText();
 }
 
+QString QgsFieldExpressionWidget::asExpression() const
+{
+  return isExpression() ? currentText() : QgsExpression::quotedColumnRef( currentText() );
+}
+
 bool QgsFieldExpressionWidget::isValidExpression( QString *expressionError ) const
 {
   QString temp;

src/gui/qgsfieldexpressionwidget.h

@@ -89,6 +89,13 @@ class GUI_EXPORT QgsFieldExpressionWidget : public QWidget
       */
     QString currentText() const;
 
+    /** Returns the currently selected field or expression. If a field is currently selected, the returned
+     * value will be converted to a valid expression referencing this field (ie enclosing the field name with
+     * appropriate quotations).
+     * @note added in QGIS 2.14
+     */
+    QString asExpression() const;
+
     //! Returns the currently used layer
     QgsVectorLayer* layer() const;
 

src/gui/symbology-ng/qgssizescalewidget.cpp

@@ -222,7 +222,7 @@ void QgsSizeScaleWidget::showEvent( QShowEvent* )
 QgsScaleExpression *QgsSizeScaleWidget::createExpression() const
 {
   return new QgsScaleExpression( QgsScaleExpression::Type( scaleMethodComboBox->itemData( scaleMethodComboBox->currentIndex() ).toInt() ),
-                                 mExpressionWidget->currentField(),
+                                 mExpressionWidget->asExpression(),
                                  minValueSpinBox->value(),
                                  maxValueSpinBox->value(),
                                  minSizeSpinBox->value(),

tests/src/gui/testqgsfieldexpressionwidget.cpp

@@ -48,6 +48,7 @@ class TestQgsFieldExpressionWidget : public QObject
     void cleanup();           // will be called after every testfunction.
 
     void testRemoveJoin();
+    void asExpression();
 
   private:
     QgsFieldExpressionWidget* mWidget;
@@ -133,6 +134,33 @@ void TestQgsFieldExpressionWidget::testRemoveJoin()
   // QVERIFY( !isValid ); TODO: the expression should not be valid anymore since the field doesn't exist anymore. Maybe we need a new expression method to get more details.
 }
 
+void TestQgsFieldExpressionWidget::asExpression()
+{
+  QgsVectorLayer* layer = new QgsVectorLayer( "point?field=fld:int&field=fld2:int&field=fld3:int", "x", "memory" );
+  QgsMapLayerRegistry::instance()->addMapLayer( layer );
+
+  QScopedPointer< QgsFieldExpressionWidget > widget( new QgsFieldExpressionWidget() );
+  widget->setLayer( layer );
+
+  // check with field set
+  widget->setField( "fld" );
+  QCOMPARE( widget->asExpression(), QString( "\"fld\"" ) );
+
+  // check with expressions set
+  widget->setField( "fld + 1" );
+  QCOMPARE( widget->asExpression(), QString( "fld + 1" ) );
+  widget->setField( "1" );
+  QCOMPARE( widget->asExpression(), QString( "1" ) );
+  widget->setField( "\"fld2\"" );
+  QCOMPARE( widget->asExpression(), QString( "\"fld2\"" ) );
+
+  // check switching back to a field
+  widget->setField( "fld3" );
+  QCOMPARE( widget->asExpression(), QString( "\"fld3\"" ) );
+
+  QgsMapLayerRegistry::instance()->removeMapLayer( layer );
+}
+
 
 QTEST_MAIN( TestQgsFieldExpressionWidget )
 #include "testqgsfieldexpressionwidget.moc"