Add qgsVariantEqual for null-aware comparison

Author: elpaso

python/core/auto_generated/qgis.sip.in

@@ -187,6 +187,17 @@ QVariant data types (such as strings, numeric values, dates and times)
 .. seealso:: :py:func:`qgsVariantGreaterThan`
 %End
 
+bool qgsVariantEqual( const QVariant &lhs, const QVariant &rhs );
+%Docstring
+Compares two QVariant values and return whether they are equal, it takes into
+account null values.
+
+:param lhs: first value
+            @param rhs second value
+            @return true if values are equal
+%End
+
+
 bool qgsVariantGreaterThan( const QVariant &lhs, const QVariant &rhs );
 %Docstring
 Compares two QVariant values and returns whether the first is greater than the second.

src/core/qgis.cpp

@@ -306,3 +306,8 @@ uint qHash( const QVariant &variant )
 
   return std::numeric_limits<uint>::max();
 }
+
+bool qgsVariantEqual( const QVariant &lhs, const QVariant &rhs )
+{
+  return lhs.isNull() == rhs.isNull() && lhs == rhs;
+}

src/core/qgis.h

@@ -448,6 +448,17 @@ CORE_EXPORT qlonglong qgsPermissiveToLongLong( QString string, bool &ok );
  */
 CORE_EXPORT bool qgsVariantLessThan( const QVariant &lhs, const QVariant &rhs );
 
+/**
+ * Compares two QVariant values and return whether they are equal, it takes into
+ * account null values.
+ *
+ * \param lhs first value
+ * @param rhs second value
+ * @return true if values are equal
+ */
+CORE_EXPORT bool qgsVariantEqual( const QVariant &lhs, const QVariant &rhs );
+
+
 /**
  * Compares two QVariant values and returns whether the first is greater than the second.
  * Useful for sorting lists of variants, correctly handling sorting of the various

src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp

@@ -185,7 +185,7 @@ void QgsValueRelationWidgetWrapper::setValue( const QVariant &value )
     for ( int i = 0; i < mComboBox->count(); i++ )
     {
       QVariant v( mComboBox->itemData( i ) );
-      if ( v.isNull() == value.isNull() && v == value )
+      if ( qgsVariantEqual( v, value ) )
       {
         idx = i;
         break;

tests/src/core/testqgis.cpp

@@ -45,6 +45,7 @@ class TestQgis : public QObject
     void qVariantCompare();
     void testQgsAsConst();
     void testQgsRound();
+    void testQgsVariantEqual();
 
   private:
     QString mReport;
@@ -359,6 +360,21 @@ void TestQgis::testQgsRound()
   QGSCOMPARENEAR( qgsRound( 9999999.87654321987654321, 14 ), 9999999.876543219876543, 0.00000000000001 );
 }
 
+void TestQgis::testQgsVariantEqual()
+{
+  QVariant lhs;
+  QVariant rhs;
+
+  QVERIFY( lhs == rhs );
+  lhs.setValue( 0 );
+  QVERIFY( lhs != rhs );
+  rhs.setValue( 0 );
+  QVERIFY( lhs == rhs );
+  lhs.setValue( 1.2345 );
+  rhs.setValue( 1.2345 );
+  QVERIFY( lhs == rhs );
+}
+
 
 QGSTEST_MAIN( TestQgis )
 #include "testqgis.moc"