expression: dump binary operations with brackets to break precedence (fixes #9783)

src/core/qgsexpression.cpp

@@ -2179,9 +2179,57 @@ bool QgsExpression::NodeBinaryOperator::prepare( QgsExpression* parent, const Qg
   return resL && resR;
 }
 
+int QgsExpression::NodeBinaryOperator::precedence() const
+{
+  // see left/right in qgsexpressionparser.yy
+  switch ( mOp )
+  {
+    case boOr:
+      return 1;
+
+    case boAnd:
+      return 2;
+
+    case boEQ:
+    case boNE:
+    case boLE:
+    case boGE:
+    case boLT:
+    case boGT:
+    case boRegexp:
+    case boLike:
+    case boIs:
+    case boIsNot:
+      return 3;
+
+    case boPlus:
+    case boMinus:
+      return 4;
+
+    case boMul:
+    case boDiv:
+    case boMod:
+      return 5;
+
+    case boPow:
+      return 6;
+
+    case boConcat:
+      return 7;
+  }
+}
+
 QString QgsExpression::NodeBinaryOperator::dump() const
 {
-  return QString( "%1 %2 %3" ).arg( mOpLeft->dump() ).arg( BinaryOperatorText[mOp] ).arg( mOpRight->dump() );
+  QgsExpression::NodeBinaryOperator *lOp = dynamic_cast<QgsExpression::NodeBinaryOperator *>( mOpLeft );
+  QgsExpression::NodeBinaryOperator *rOp = dynamic_cast<QgsExpression::NodeBinaryOperator *>( mOpRight );
+
+  QString fmt;
+  fmt += lOp && lOp->precedence() < precedence() ? "(%1)" : "%1";
+  fmt += " %2 ";
+  fmt += rOp && rOp->precedence() < precedence() ? "(%3)" : "%3";
+
+  return fmt.arg( mOpLeft->dump() ).arg( BinaryOperatorText[mOp] ).arg( mOpRight->dump() );
 }
 
 //

src/core/qgsexpression.h

@@ -441,6 +441,8 @@ class CORE_EXPORT QgsExpression
         virtual bool needsGeometry() const { return mOpLeft->needsGeometry() || mOpRight->needsGeometry(); }
         virtual void accept( Visitor& v ) const { v.visit( *this ); }
 
+        int precedence() const;
+
       protected:
         bool compare( double diff );
         int computeInt( int x, int y );

src/core/qgsvectorlayerrenderer.cpp

@@ -68,7 +68,7 @@ QgsVectorLayerRenderer::QgsVectorLayerRenderer( QgsVectorLayer* layer, QgsRender
   if ( !mRendererV2 )
     return;
 
-  QgsDebugMsg( "rendering v2:\n" + mRendererV2->dump() );
+  QgsDebugMsg( "rendering v2:\n  " + mRendererV2->dump() );
 
   if ( mDrawVertexMarkers )
   {

src/gui/symbology-ng/qgsdatadefinedsymboldialog.cpp

@@ -1,6 +1,7 @@
 #include "qgsdatadefinedsymboldialog.h"
 #include "qgsexpressionbuilderdialog.h"
 #include "qgsvectorlayer.h"
+#include "qgslogger.h"
 #include <QCheckBox>
 #include <QComboBox>
 #include <QPushButton>
@@ -104,7 +105,7 @@ QMap< QString, QString > QgsDataDefinedSymbolDialog::dataDefinedProperties() con
 
 void QgsDataDefinedSymbolDialog::expressionButtonClicked()
 {
-  qWarning( "Expression button clicked" );
+  QgsDebugMsg( "Expression button clicked" );
 
   //find out row
   QObject* senderObj = sender();

tests/src/core/testqgsexpression.cpp

@@ -432,6 +432,18 @@ class TestQgsExpression: public QObject
       }
     }
 
+    void eval_precedence()
+    {
+      QgsExpression e0( "1+2*3" );
+      QCOMPARE( e0.evaluate().toInt(), 7 );
+
+      QgsExpression e1( "(1+2)*(3+4)" );
+      QCOMPARE( e1.evaluate().toInt(), 21 );
+
+      QgsExpression e2( e1.dump() );
+      QCOMPARE( e2.evaluate().toInt(), 21 );
+    }
+
     void eval_columns()
     {
       QgsFields fields;