Show NULL preview text in expression editor

nyalldawson · nyalldawson · commit cfc3a86001b3 · 2017-01-11T12:56:24.000+10:00
Makes creating/debugging expressions easier for users

(cherry-picked from 1f3723)
diff --git a/src/core/qgsexpression.cpp b/src/core/qgsexpression.cpp
@@ -5207,6 +5207,10 @@ QString QgsExpression::formatPreviewString( const QVariant& value )
     else
       return tr( "<i>&lt;geometry: %1&gt;</i>" ).arg( QgsWKBTypes::displayString( geom.geometry()->wkbType() ) );
   }
+  else if ( !value.isValid() )
+  {
+    return tr( "<i>NULL</i>" );
+  }
   else if ( value.canConvert< QgsFeature >() )
   {
     //result is a feature

Original file line number	Diff line number	Diff line change
`@@ -5207,6 +5207,10 @@ QString QgsExpression::formatPreviewString( const QVariant& value )`
`5207`	`5207`	`else`
`5208`	`5208`	`return tr( "<i><geometry: %1></i>" ).arg( QgsWKBTypes::displayString( geom.geometry()->wkbType() ) );`
`5209`	`5209`	`}`
	`5210`	`+ else if ( !value.isValid() )`
	`5211`	`+ {`
	`5212`	`+ return tr( "<i>NULL</i>" );`
	`5213`	`+ }`
`5210`	`5214`	`else if ( value.canConvert< QgsFeature >() )`
`5211`	`5215`	`{`
`5212`	`5216`	`//result is a feature`