No that is dangerous, consider this:

    set -e
    myfunc() {
      date %x  # syntax error; returns 1, should be +%x
      echo 'should not get here'
    }

    if var=$(myfunc); then
      echo $var   # erroneously prints 'should not get here'
    else
      echo failed
    fi

Then you will ignore failure, which is bad.

This is a variant of the issue that the sibling comment brought up -- error handling is disabled inside "if" conditions.

In Oil the whole construct is unconditionally disabled by strict_errexit. It's too subtle.

Oil has 2 ways of capturing the exit code, including

    run --assign :status -- mycommand  # exit 0 but assign the status to a var

and

    shopt --unset errexit {  # explicitly disable error handling if you want
      mycmd
      var status = $?
    }

I'm looking for feedback to make sure that Oil has indeed fixed all of this stuff: https://www.oilshell.org/blog/2020/10/osh-features.html

Basically the situation is "damned if you do and damned if you don't" in Bourne shell, so you need language/interpreter changes to really fix it. The rules are too tricky to remember even for shell experts -- there are persistent arguments on POSIX behavior that is over 20 years old, simply because it's so confusing.

https://github.com/oilshell/oil/wiki/Where-To-Send-Feedback