$_ does not work correctly in functions called from test

[tooptoop4]

my code file (mycode.sh) has:

function urldecode() { : "${*//+/ }"; echo -e "${_//%/\\x}"; }
if [ "${0##*/}" = mycode.sh ]; then
echo do_stuff
fi

my test file has:

. mycode.sh

@test "urldecode test" {
    urldecode 'day%3D29' | grep -qFx 'day=29'
}

To Reproduce
/usr/local/bin/bats /fol/tes.sh fails it seems to get the output of filename instead of day

Expected behavior
test should pass

Environment (please complete the following information):

• Bats version: Bats 1.10.0
• operating system (including version): Debian GNU/Linux 11 (bullseye)
• bash --version: GNU bash, version 5.1.4(1)-release (x86_64-pc-linux-gnu)
• Install method: git

[martin-schulze-vireso]

This is most likely a bad interaction with the debug trap. I am afraid we can't do much about that since the debug trap is needed. However, you can likely work around that by not calling your function directly in the test but under run.

I think this would warrant a section in the gotchas documentation.

Once you are using run, I would suggest you also use assert_output from the bats-assert library to get better diagnostics. This would be the resulting code:

setup() {
  # sourcing in setup gives better diagnostics than in free code
  . mycode.sh
  bats_load_library bats-support # needed as helper for bats-assert
  bats_load_library bats-assert
}

@test "urldecode test" {
    run urldecode 'day%3D29' 
    assert-output 'day=29'
}