i had to move from mojave to catalina during the beta to test some security tooling for work (spoilers: it sucked, though now cylance has actually fixed their catalina problems) and the process was r o u g h almost entirely because of emacs.
at first there was only a single reddit post detailing what emacs users might need to know about. it linked to this gist.
this basically says to run this lisp to add your proper emacs path to the proper exclusions and then you won't have any problems. Ok great! but that didn't work. I could now launch emacs from Spotlight and navigate around my Docs/Downloads/whatever, but i was totally unable to swap to emacs from Spotlight. this also impacted using hammerspoon as a launcher, i'm guessing because the primative behind both mechanisms is the same.
later that week, a few other people said you needed to whitelist ruby's executable because that was actually how homebrew installed emacs; the emacs executable is called from a ruby script (which is called by a ball rolling down a train track headed towards a toothpick which,) and thus needs to be whitelisted as well. but that didn't work either (though they were actually correct that ruby was involved).
since I could at least launch and navigate around with my then-current janky set up i stopped spending Paid Time on it and moved on. i ran the the rest of the catalina beta out and then reported back on my experience with our security tools, whatever. a few weeks ago i finally got mad enough at the situation to spend some more time looking at this and found the answer really soon! apparently a bunch of people had similar problems to me and so there are several blogs about the problem now! the one I found most helpful was this guy.
he gives a good breakdown as to why this is needed instead of the ruby application whitelisting. here's the quick fix:
% cd /Applications /Emacs.app /Contents /MacOS % mv Emacs Emacs-launcher % mv Emacs-x86_64- 10_14 Emacs % cd /Applications /Emacs.app /Contents / % rm -rf _CodeSignature
this is not like, super great. its makes your configuration brittle and it will break when you update emacs! version 27 is looming i hear. but at least i can fucking swap to emacs again.