Exceptions for SC2181

[qianbinbin]

Hi there,

Say we defined a function f() in a subshell with set -e, and call it with error check:

#!/usr/bin/env sh

f() (
  set -e
  echo Executing
  false
  echo Should NOT get HERE
)

f || echo Error

If we call it with f || echo Error or if statement as suggested in https://github.com/koalaman/shellcheck/wiki/SC2181 , the output will be:

Executing
Should NOT get HERE

Which is not what we want.

While this

f
[ "$?" -eq 0 ] || echo Error

works as expected, so I think this would be an exception.

[aeiplatform]

Good practice is to avoid one-liner for future maintenance.

if ! f; then In this case you can always add functionality without any refactoring (just adding lines)

[aeiplatform]

For more complex error handling you have to store exit code into variable for case statement, etc

[dslatkin]

Had a similar issue.

I ended up making it work with traps, but that needs bash. I think traps are a bit nicer since it sidesteps the issue of checking $? and the legitimate complaints associated with it from shellcheck.

That looks something like this, applying it to the original example:

#!/bin/bash

handle_error () (
    echo "Handling error"
)

call_func () (
    set -e
    trap 'handle_error' ERR

    echo "Executing"
    false
    echo "Should not get here"
)

call_func

To keep shellcheck quiet while using POSIX shell takes something similar to first store it in a variable:

#!/usr/bin/env sh

call_func () (
    set -e

    echo "Executing"
    false
    echo "Should not get here"
)

call_func
func_result=$?
if [ "$func_result" -ne 0 ]; then
    echo "Handling error"
fi