[Incorrect file picker on some Linux distros] File name extension isn’t correctly added (save dialog)

Issue type

Opening/saving issue

Description with steps to reproduce

1. Open a score and “save” or “save as” (on disk, not cloud).
2. In the save dialog, choose .mscz file type/extension from the dropdown at the bottom.
3. Type in the file base name without extension (e. g. “my_cool_song”).
4. Save.
   Expected behaviour: MuseScore saves as zip/mscz file “my_cool_song.mscz”.
   Actual behaviour: MuseScore saves as folder “my_cool_song” containing “my_cool_song.mscx” and other files.

Supporting files, videos and screenshots

In which versions of MuseScore Studio is this issue present?

MuseScore 4.7.3, Qt 6.10.2

Regression

Yes, this used to work in a previous version of MuseScore 4.x

Operating system

Manjaro Linux

Additional context

It’s a regression but I’m not sure whether it’s a MuseScore or Qt problem. IIRC it already hadn’t worked in some version 4.x but then it worked again so I didn’t file a bug report.

Checklist

• This report follows the guidelines for reporting bugs and issues
• I have verified that this issue has not been logged before, by searching the issue tracker for similar issues
• I have attached all requested files and information to this report
• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible

Start by reproducing the save-dialog flow on Manjaro Linux with MuseScore 4.7.3 and Qt 6.10.2, then trace the handling of the selected .mscz extension when the base name has no extension. Done means saving produces my_cool_song.mscz rather than a folder containing .mscx and other files, with the regression covered by an appropriate test if the existing test structure allows it.