Last night I upgraded my MacBook Pro to macOS Catalina (macOS 10.15). I’d been holding off to see if there were reports of problems with Emacs on the new OS. That happened last time with the upgrade to Mojave because Apple stopped supporting the old display model and you couldn’t use Emacs in GUI mode until the Emacs devs generated a fix.
This time, there were reports of Emacs not being able to access (any of) the file system. The solution seemed pretty simple. The TL;DR is that Emacs was being loaded by a Ruby script so it was Ruby that needed to be given permissions. I hadn’t heard of the Ruby script before but assumed it was something new in Emacs 27. When I checked the above Stack Exchange entry, though, it said the poster was seeing the problem in Emacs 26.1.
In any event, after the upgrade Emacs worked just fine without me doing anything. I’m using the same binary (Emacs 26.3 compiled from source) as before so I haven’t tried recompiling Emacs yet but the old binary is working as it was previously without having to adjust permissions or anything else. My conclusion is that there’s no reason not to upgrade as far as Emacs is concerned. If you do experience problems with accessing the file system, take a look at the above link. Every report I saw about the problem said that the solution provided by Stack Exchange got things working again.
Added in editing:
Here’s a tweet that also describes the problem. The Stack Exchange link it contains is different from the one above so you should look at it too if you’re having problems.
You must provide full disk access for /usr/bin/ruby to make #Emacs work correctly on #Mac #Catalina. More details are here: https://t.co/KgzxC0THy7 Thanks, @wsaleem pic.twitter.com/gkmNg1QjBO
— Advaita Krishna das (@ak_dasa) October 17, 2019