err_exit misbehaviour involving function call inside else

[okdana]

(workers/42126)

The following script prints 0 in ksh93, dash, and bash, but 1 in zsh:

fn() { return 1; }
(
  set -e
  if [ x = y ]; then
    fn || :
  else
    fn || :
  fi
  :
)
echo $?

It doesn't attempt to execute the || : part at all, just immediately returns
after fn.

It seems like it has something to do specifically with calling a function inside
the body of an else. If i change x = y to x = x, then the first fn || :
behaves as expected. Or if i change fn to false, that works too. Or if i
remove the conditional entirely.

Bart replied:

See the thread w/Subject: "set -e" handling is broken with zsh 5.3.1 and 5.4.1

In particular workers/41608 and workers/41615 ... I wonder if you have
found the regression that wasn't found at the time of that patch.

At the very least this sounds related.

Still an issue in 5.5.1.