This question is about how the scanner treats empty folders.
There is an option on the scanner that allows the user to check for unused files and fix (remove) them. I have found that the scanner only checks for unused files and does not check for unused or empty folders. This came up when re-scanning a set that formerly had a hash name collision, but was changed by a MAMEdev to have unique names. clrmamepro moved the file to the new name in the root of the .7z file, but the folder it formerly occupied (now empty), was left in the .7z file. I found I could add any number of empty folders to a .7z file, let clrmamepro scan it, with the "fix unused" checkbox set, and clrmamepro leaves them in the .7z file. I suppose this behavior could be an artifact of the communication with the 7-zip.exe file as specified in the compressor properties dialog, but I thought I would ask about it in case it was something that is being overlooked. I'm using 7-Zip [64] 9.38 beta.
The file I found that this happened to is "fm7_cass\gbank.7z" in the MAME Software Lists.
Of course the rebuilder does not have this issue, it only rebuilds what is necessary and never adds the empty folders. Certainly a valid work-around is to rebuild everything each time MAME is updated. But that's going to take a long time, as the .7z file handling takes so much longer than the .zip file handling.
Thanks for entertaining my questions. I realize these points are minor, and I understand if they are low priority to address, or not even worth addressing.