do not override QDateTimeEdit::dateTimeChanged

see KDE/clazy@de03186#diff-f135574df9edcdda660e1bc4320a053e

python/gui/editorwidgets/qgsdatetimeedit.sip

@@ -15,8 +15,8 @@ class QgsDateTimeEdit : QDateTimeEdit
 
 .. warning::
 
-   You should use the signal dateTimeChanged of this subclass QgsDateTimeEdit
-rather than parent's one (QDateTimeEdit). If you consequently connect parent's
+   You should use the signal valueChanged of this subclass
+rather than QDateTimeEdit.dateTimeChanged. If you consequently connect parent's
 dateTimeChanged signal and call dateTime() afterwards there is no warranty to
 have a proper NULL value handling.
 %End
@@ -74,10 +74,9 @@ Resets the widget to show no value (ie, an "unknown" state).
 
   signals:
 
-    void dateTimeChanged( const QDateTime &date );
+    void valueChanged( const QDateTime &date );
 %Docstring
-reimplements QDateTimeEdit.dateTimeChanged signal
-to properly handles NULL values.
+signal emitted whenever the value changes.
 @param date the new date/time value.
 %End
 

src/gui/editorwidgets/qgsdatetimeedit.cpp

@@ -61,6 +61,15 @@ void QgsDateTimeEdit::clear()
     displayNull();
 
     changed( QDateTime() );
+
+    // emit signal of QDateTime::dateTimeChanged with an invalid date
+    // anyway, using parent's signal should be avoided
+    // If you consequently connect parent's dateTimeChanged signal
+    // and call dateTime() afterwards there is no warranty to
+    // have a proper NULL value handling
+    disconnect( this, &QDateTimeEdit::dateTimeChanged, this, &QgsDateTimeEdit::changed );
+    emit dateTimeChanged( QDateTime() );
+    connect( this, &QDateTimeEdit::dateTimeChanged, this, &QgsDateTimeEdit::changed );
   }
 }
 
@@ -170,7 +179,7 @@ void QgsDateTimeEdit::changed( const QDateTime &dateTime )
 
   mClearAction->setVisible( mAllowNull && !mIsNull );
 
-  emit QgsDateTimeEdit::dateTimeChanged( dateTime );
+  emit QgsDateTimeEdit::valueChanged( dateTime );
 }
 
 void QgsDateTimeEdit::displayNull( bool updateCalendar )

src/gui/editorwidgets/qgsdatetimeedit.h

@@ -24,8 +24,8 @@
  * \ingroup gui
  * \brief The QgsDateTimeEdit class is a QDateTimeEdit with the capability of setting/reading null date/times.
  *
- * \warning You should use the signal dateTimeChanged of this subclass QgsDateTimeEdit
- * rather than parent's one (QDateTimeEdit). If you consequently connect parent's
+ * \warning You should use the signal valueChanged of this subclass
+ * rather than QDateTimeEdit::dateTimeChanged. If you consequently connect parent's
  * dateTimeChanged signal and call dateTime() afterwards there is no warranty to
  * have a proper NULL value handling.
  */
@@ -70,11 +70,10 @@ class GUI_EXPORT QgsDateTimeEdit : public QDateTimeEdit
   signals:
 
     /**
-     * reimplements QDateTimeEdit::dateTimeChanged signal
-     * to properly handles NULL values.
+     * signal emitted whenever the value changes.
      * @param date the new date/time value.
      */
-    void dateTimeChanged( const QDateTime &date );
+    void valueChanged( const QDateTime &date );
 
   protected:
     void mousePressEvent( QMouseEvent *event ) override;

src/gui/editorwidgets/qgsdatetimeeditwrapper.cpp

@@ -93,7 +93,7 @@ void QgsDateTimeEditWrapper::initWidget( QWidget *editor )
 
   if ( mQgsDateTimeEdit )
   {
-    connect( mQgsDateTimeEdit, &QgsDateTimeEdit::dateTimeChanged, this, &QgsDateTimeEditWrapper::dateTimeChanged );
+    connect( mQgsDateTimeEdit, &QgsDateTimeEdit::valueChanged, this, &QgsDateTimeEditWrapper::dateTimeChanged );
   }
   else
   {