How to trap EXIT unconditionally (even if interrupted), in Zsh?

Question

I would like to trap the exit hook of a function. Bash provides a nice signal called RETURN (non-POSIX) which get called when a function returns, such as

function test_trap() {
    trap 'echo trapped' RETURN
    sleep 10  # simulate time-consuming commands
    echo done
}

I see “trapped” when the function returns, even if I send a SIGINT with Ctrl C. Is there similar functionality for Zsh? I tried EXIT in Zsh, but it only traps normal returns, not when I interrupt with SIGINT. I also tried trapping both EXIT and INT with the same hook function, but it has two issues:

1. The hook expression is evaluated twice when I interrupt it. No big deal; my hook expression happens to be idempotent.
2. The EXIT in Zsh is local: when returning from the function, the original hook is recovered. This is similar to how a local variable shadows a global one. Unfortunately, the INT hook is always global, so any hook I specify will overwrite the global one. I would need to remember the original INT hook, and recover it later. It’s very tricky to do it correctly; I may have a try on this.

Answer 1

That's like for the EXIT trap outside of functions. Exiting and being killed are two different things.

So like outside of functions, you need to handle them separately:

test_trap() {
  set -o localoptions -o localtraps
  trap 'echo "I am exiting."' EXIT
  trap 'echo "I have been interrupted, so"; return 1' INT

  echo start
  sleep 10
  echo end
}

test_trap
echo "returned with: $?"

Which gives:

$ zsh ./that-script
start
^CI have been interrupted, so
I am exiting.
returned with: 1

If you want the shell (not just the function) to exit when it handles the SIGINT signal when received while executing the function, replace return 1 with exit (or kill yourself with SIGINT after having restored the default handler (trap - INT; kill -s INT "$$") if you want to report your death by signal to your parent).