Mojave Drag and Drop not processing files as one list (one drop event)

Mojave v10.4.3 has a rather insidious bug in the code related to Drag-and-Drop. It almost looks as if the event handler is firing twice for one Drag-and-Drop action. This manifests itself as the app appearing to receive two lists of dropped files, instead of just one. This is further complicated by the observation that it only behaves this way for when certain filetypes are part of the set dropped. To date TIF, PDF and DMG files seem to be affected. MP3 and WEBLOC are not. There may be (and likely are) others.

This issue can be a nightmare when developing apps, so I thought it best to post it here. Hopefully, this keeps others from the sleepless nights I’ve had. :>)


I can’t reproduce this

This feature was described several times. It strikes when some moved files have quarantine bit set and others haven’t.

Yvan KOENIG running High Sierra 10.13.6 in French (VALLAURIS, France) dimanche 24 février 2019 12:07:49


I finally have an answer to the issue. The upgrade to Mojave is apparently not clean. Others, who I presume have upgraded rather than done a clean install, have had the same issue. So; I don’t believe it was something I did on my machine. I re-imaged my computer completely and now the drag and drop works fine. I should have suspected that the upgrade to Mojave would have issues.



I think you must be correct. It’s back!
This “bug” is a real issue for processing data files with drag and drop.
Removing the quarantine attribute doesn’t sound like a permanent solution.
Was there a fix posted by anyone?

Calgary, Alberta

First, it’s not a feature introduced by Mojave. I exchanged about that with Shane STANLEY in February 2017 when the OS was Sierra.
One soluce is to use a script to clear the offending bit.
Some days ago I read a Shane’s answer which urged to move the files in an other folder process which, if I understood well, would clear the bit.

Yvan KOENIG running High Sierra 10.13.6 in French (VALLAURIS, France) mardi 26 février 2019 10:44:56

Thank you, Yvan. I too remember that suggestion to move the files. However; I ended up writing a script to clear the Quarantine portion of the extended attributes from selected files instead. Moving my files around to overcome this issue is most inconvenient, since I have thousands of them.

The files in question were generated on my system by my scanning old documents. There should be no logical reason why the Quarantine attribute was set by the system, yet it was. Apple wants to protect external code from running without being given permission to run. However; the process they use to evaluate which files are reasonable to “Quarantine” appears to be flawed.

As this “feature” (aka “bug”) appears to have been around for a while, I really hope they fix it soon. I called Apple about this and even their support supervisor did not seem to be aware that this problem was still present in Mojave. In the absence of a proper fix by Apple, I may write a daemon to watch certain directories and remove the offending attribute from particular classes of files.

My experience has been similar to Gary’s. However, moving files to a new folder sometimes works and sometimes does not. Using a script to clear quarantine bits usually works, but not always. If I could devote many hours to this using a wide variety of systems, perhaps I could report back with something which could be reliably replicated. But even if I had time for full testing and bug reporting, I’m very doubtful any user report would lead to an improvement. Pessimistic? Yes.