improve field conversions (fixes #12004)

Author: jef-n

src/app/qgsattributetabledialog.cpp

@@ -332,7 +332,6 @@ void QgsAttributeTableDialog::runFieldCalculation( QgsVectorLayer* layer, QStrin
   bool calculationSuccess = true;
   QString error;
 
-
   QgsExpression exp( expression );
   exp.setGeomCalculator( *myDa );
   bool useGeometry = exp.needsGeometry();
@@ -342,6 +341,8 @@ void QgsAttributeTableDialog::runFieldCalculation( QgsVectorLayer* layer, QStrin
 
   int rownum = 1;
 
+  const QgsField &fld = layer->pendingFields()[ fieldindex ];
+
   //go through all the features and change the new attributes
   QgsFeatureIterator fit = layer->getFeatures( request );
   QgsFeature feature;
@@ -354,6 +355,7 @@ void QgsAttributeTableDialog::runFieldCalculation( QgsVectorLayer* layer, QStrin
 
     exp.setCurrentRowNumber( rownum );
     QVariant value = exp.evaluate( &feature );
+    fld.convertCompatible( value );
     // Bail if we have a update error
     if ( exp.hasEvalError() )
     {

src/core/qgsfield.cpp

@@ -137,17 +137,32 @@ bool QgsField::convertCompatible( QVariant& v ) const
     return true;
   }
 
+  if ( mType == QVariant::Int && v.toInt() != v.toLongLong() )
+  {
+    v = QVariant( mType );
+    return false;
+  }
+
   if ( !v.convert( mType ) )
   {
+    v = QVariant( mType );
     return false;
   }
 
   if ( mType == QVariant::Double && mPrecision > 0 )
   {
-    v = qRound64( v.toDouble() * qPow( 10, mPrecision ) ) / qPow( 10, mPrecision );
+    double s = qPow( 10, mPrecision );
+    double d = v.toDouble() * s;
+    v = QVariant(( d < 0 ? ceil( d - 0.5 ) : floor( d + 0.5 ) ) / s );
     return true;
   }
 
+  if ( mType == QVariant::String && mLength >= 0 && v.toString().length() > mLength )
+  {
+    v = QVariant( mType );
+    return false;
+  }
+
   return true;
 }
 

src/gui/editorwidgets/qgstexteditwrapper.cpp

@@ -58,8 +58,12 @@ QVariant QgsTextEditWrapper::value()
   if (( v.isEmpty() && ( field().type() == QVariant::Int || field().type() == QVariant::Double || field().type() == QVariant::LongLong || field().type() == QVariant::Date ) ) ||
       v == QSettings().value( "qgis/nullValue", "NULL" ).toString() )
     return QVariant( field().type() );
+
+  QVariant res( v );
+  if ( field().convertCompatible( res ) )
+    return res;
   else
-    return QVariant( v );
+    return QVariant( field().type() );
 }
 
 QWidget* QgsTextEditWrapper::createWidget( QWidget* parent )