Convert values to target field format

For the field calculator and virtual fields.

Fix #11000
Fix #10995
Fix #10993

Author: m-kuhn

python/core/qgsfield.sip

@@ -110,6 +110,65 @@ public:
 
     /**Formats string for display*/
     QString displayString( const QVariant& v ) const;
+
+
+    /**
+     * Converts the provided variant to a compatible format
+     *
+     * @param v  The value to convert
+     *
+     * @return   True if the conversion was successful
+     */
+    QVariant convertCompatible( QVariant& v ) const;
+%MethodCode
+    PyObject *sipParseErr = NULL;
+
+    {
+      QVariant * a0;
+      int a0State = 0;
+      const QgsField *sipCpp;
+
+      if (sipParseArgs(&sipParseErr, sipArgs, "BJ1", &sipSelf, sipType_QgsField, &sipCpp, sipType_QVariant,&a0, &a0State))
+      {
+        bool sipRes;
+
+        Py_BEGIN_ALLOW_THREADS
+        try
+        {
+          QgsDebugMsg( a0->toString() );
+          sipRes = sipCpp->convertCompatible(*a0);
+          QgsDebugMsg( a0->toString() );
+        }
+        catch (...)
+        {
+          Py_BLOCK_THREADS
+
+          sipReleaseType(a0,sipType_QVariant,a0State);
+            sipRaiseUnknownException();
+            return NULL;
+        }
+
+        Py_END_ALLOW_THREADS
+
+        PyObject* res = sipConvertFromType( a0, sipType_QVariant, NULL );
+        sipReleaseType(a0,sipType_QVariant,a0State);
+
+        if ( !sipRes )
+        {
+          PyErr_SetString(PyExc_ValueError,
+            QString( "Value %1 (%2) could not be converted to field type %3." ).arg( a0->toString() ).arg ( a0->typeName() ).arg( sipCpp->type() ).toUtf8().constData() );
+            sipError = sipErrorFail;
+        }
+
+        return res;
+      }
+    }
+
+    /* Raise an exception if the arguments couldn't be parsed. */
+    sipNoMethod(sipParseErr, sipName_QgsField, sipName_convertCompatible, doc_QgsField_convertCompatible);
+
+    return NULL;
+%End
 }; // class QgsField
 
 

src/app/qgsfieldcalculator.cpp

@@ -127,6 +127,8 @@ void QgsFieldCalculator::accept()
     return;
   }
 
+  const QgsField& field = mVectorLayer->pendingFields()[mAttributeId];
+
   QApplication::setOverrideCursor( Qt::WaitCursor );
 
   mVectorLayer->beginEditCommand( "Field calculator" );
@@ -198,7 +200,7 @@ void QgsFieldCalculator::accept()
   bool newField = !mUpdateExistingGroupBox->isChecked();
   QVariant emptyAttribute;
   if ( newField )
-    emptyAttribute = QVariant( mVectorLayer->pendingFields()[mAttributeId].type() );
+    emptyAttribute = QVariant( field.type() );
 
   QgsFeatureIterator fit = mVectorLayer->getFeatures( QgsFeatureRequest().setFlags( useGeometry ? QgsFeatureRequest::NoFlags : QgsFeatureRequest::NoGeometry ) );
   while ( fit.nextFeature( feature ) )
@@ -210,9 +212,9 @@ void QgsFieldCalculator::accept()
         continue;
       }
     }
-
     exp.setCurrentRowNumber( rownum );
     QVariant value = exp.evaluate( &feature );
+    field.convertCompatible( value );
     if ( exp.hasEvalError() )
     {
       calculationSuccess = false;

src/core/qgsfield.cpp

@@ -17,6 +17,7 @@
 #include "qgsfield.h"
 
 #include <QSettings>
+#include <QtCore/qmath.h>
 
 #if 0
 QgsField::QgsField( QString nam, QString typ, int len, int prec, bool num,
@@ -128,6 +129,27 @@ QString QgsField::displayString( const QVariant& v ) const
   return v.toString();
 }
 
+bool QgsField::convertCompatible( QVariant& v ) const
+{
+  if ( v.isNull() )
+  {
+    v.convert( mType );
+    return true;
+  }
+
+  if ( !v.convert( mType ) )
+  {
+    return false;
+  }
+
+  if ( mType == QVariant::Double && mPrecision > 0 )
+  {
+    v = qRound64( v.toDouble() * qPow( 10, mPrecision ) ) / qPow( 10, mPrecision );
+    return true;
+  }
+
+  return true;
+}
 
 ////////////////////////////////////////////////////////////////////////////
 

src/core/qgsfield.h

@@ -129,6 +129,15 @@ class CORE_EXPORT QgsField
     /** Formats string for display*/
     QString displayString( const QVariant& v ) const;
 
+    /**
+     * Converts the provided variant to a compatible format
+     *
+     * @param v  The value to convert
+     *
+     * @return   True if the conversion was successful
+     */
+    bool convertCompatible( QVariant& v ) const;
+
   private:
 
     //! Name

src/core/qgsvectorlayerfeatureiterator.cpp

@@ -559,6 +559,7 @@ void QgsVectorLayerFeatureIterator::addVirtualAttributes( QgsFeature& f )
     {
       QgsExpression* exp = it.value();
       QVariant val = exp->evaluate( f );
+      mSource->mFields.at( it.key() ).convertCompatible( val );;
       f.setAttribute( it.key(), val );
     }
   }