The action script contains set -e which tells bash to exit if any command fails:

Further down however it expects to be able to capture the exit code of executing the reviewdog binary:

But any non zero code would cause a termination before reaching that line.

Essentially the following might give the impression that some cleanup is done if the reviewdog command fails, but it's not, if the exit code is anything other than 0, the following block never gets run:

EXIT_CODE=$?

if [ "${INPUT_CLEANUP}" = "true" ]; then
  git stash drop || true
else
  git stash pop || true
fi

exit "${EXIT_CODE}"

Previously there was an || EXIT_CODE=$? that was removed as part of https://github.com/reviewdog/action-suggester/pull/31/files but this doesn't see correct if errexit is set

Instead it would appear that the command should use an && as well as an || to capture the exit code on the same line and ensure the line exit code is 0:

reviewdog \
  -name="${INPUT_TOOL_NAME:-reviewdog-suggester}" \
  -f=diff \
  -f.diff.strip=1 \
  -reporter="github-pr-review" \
  -filter-mode="${INPUT_FILTER_MODE}" \
  -fail-on-error="${INPUT_FAIL_ON_ERROR}" \
  -level="${INPUT_LEVEL}" \
  ${INPUT_REVIEWDOG_FLAGS} <"${TMPFILE}" && EXIT_CODE=$? || EXIT_CODE=$?