qSetMessagePattern() doesn't work inside the debugger

I notice two different output with the following program:

 #include <QCoreApplication>
 #include <QDebug>

int main(int argc, char *argv[]) {
 QCoreApplication a(argc, argv);

qSetMessagePattern("message: %

{message}

");
 qDebug() << "A debug message";
 return 0;
 }
 

If I run it normally I have the expected output:

 message: A debug message

If I run the debugger instead, I have the following output:

 2019-06-07 15:40:40.706939+0200 category-logging[49221:2034723] A debug message

As you can see the `qSetMessagePattern()` call is not taken into account.

I check with Qt 5.9.8 and it runs fine.