macOS: QFileDialog::getSaveFileName() truncates a compound extension

Code

#include <QApplication>
#include <QFileDialog>
#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    qDebug() << QFileDialog::getSaveFileName(nullptr, "Caption", "MyFile", "Archive (*.tar.gz)");
}

Expected results (Windows/Linux)

• The default filename in the dialog is "MyFile.tar.gz"
• If you manually change the filename in the dialog to "abc", the debug output shows "abc.tar.gz"

Actual results (macOS)

• The default filename in the dialog is "MyFile.gz"
• If you manually change the filename in the dialog to "abc", the debug output shows "abc.gz"

Original Report

Using QFileDialog::getSaveFileName() with a file filter of:

"All NASA/FUN3D files (*.b8.ugrid *.mapbc);;NASA/FUN3D b8.ugrid files (*.b8.ugrid);;NASA/FUN3D mapbc files (*.mapbc);;All files (*)"

If the user enters just a basename (no extension) in the dialog box, QFileDialog::getSaveFileName() returns basename.ugrid instead of the expected basename.b8.ugrid (the first filter's extension). The .b8 is getting culled by the dialog.

Linux and winOS both return basename.b8.ugrid as expected.