Command line testing of "if" works different if in interactive shell or script shell

Assume you have a dir named 'test' and inside that dir you have 'static'

mkdir -p test/static

Then assume you have this script as test.sh:

#!/bin/sh

set -xe

#arg is the directory to test if it's a ultima dir
is_static() {
  ls "$1" 2> /dev/null  | grep -qim1 '^static/$'
  return $?
}

if is_static "$1"
then
  echo 'is static'
fi

chmod +x test.sh

The output of this script here is:

$ ./test.sh 'test'
+ is_static test
+ ls test
+ grep -qim1 ^static/$
+ return 1

This is already surprising to me, but i was thinking it was a bug on the function, no big deal

but then i tested it by copy pasting the function in the file in the terminal and calling the if manually:

copy paste the is_static function into the terminal then write:

set -ex; if is_static 'test' ; then echo "success" ; fi ; set -ex

the output is:

+ set -ex
+ is_static test
+ grep --color=auto -qim1 '^static/$'
+ ls -F test
+ return 0
+ echo success
success
+ set -ex

what the hell is going on? Why is the grep and ls call inverted in the interactive shell, and why does it work there and not in the non-interactive script? And how can i make the script work?

I understand the interactive shell adds default arguments, that's not a big deal... except if i add '-F' to the ls in the function in the script suddenly the script 'works' but since -F is:

   -F, --classify
          append indicator (one of */=>@|) to entries

I'm 100% certain it's a red erring (but i'm still not certain why it fixes it).

As mentioned by oguz ismail the problem is that -F is necessary for the grep test to work because otherwise it doesn't add '/' to the output directories. This is the default in ubuntu, but not on non-interactive shells.

I ended up doing:

find "$1" -mindepth 1 -maxdepth 1 -type d -iname "static" -print -quit | grep '.' > /dev/null; return "$?"

Which is much more confusing but seems that it might be 'safer' for unusual paths or filenames.

To explain it, find can check without case sensitivity (iname) and only the "$1" contents (without '.' with -mindepth 1), only the immediate children with -maxdepth 1 and outputs the 'rest' of the path (not "$1").

Since with -print and -quit only one './static' (for success, in whatever case) or empty string (for failure) will be put into the pipe, grep '.' (any character) can test it, and i'm not using -q on the grep and instead > /dev/null 2>&1 (i'd prefer &> /dev/null but it's not posix compliant) for a pipe failure signal not to be sent to find since some shell contexts do not tolerate pipefail.

edit: changed that last part to > /dev/null. Suppressing stderr sounds like a bad idea.