Shell sucks; tried in bash, zsh, BSD sh

sh-subshell-errexit-test.sh

#!/bin/bash

script_name="$(basename "$0")"

die() {
  local rv=$?
  printf >&2 "%s: %s\n" "$script_name" "$*"
  exit $rv
}

will_fail_return() {
  echo "in will_fail_return"
  return 42
}

(
  set -e -u
  set +o
  will_fail_return
  echo $?
  echo "got to end of subshell"
) || die "subshell failed"
echo "reached end of entire script"

Of course. The problem is that -e must be somewhere defined to exit at the end of a scope of execution, which includes the entire subshell. So -e will never exit early inside a sub-shell. Moving the set -e -u above the sub-shell doesn't change things.
GRRRARGH.

It's not that. It's because of the || die at the end of the sub-shell, which changes how -e is applied within the subshell. Without || die, -e will cause an early exit. But with -e not in effect within the subshell, this is ... horrible.

So, need to do explicit die afterwards.

Oh fscking eww.