checkstyle pre-commit hook

checkstyle-pre-commit.bash

#!/usr/bin/env bash
set -euf -o pipefail

function cleanup {
    # Reset the trap handler so it's not called twice
    trap - EXIT
}

trap cleanup EXIT

####
## Main Body

CHECKSTYLE_URL="https://github.com/checkstyle/checkstyle/releases/download/checkstyle-8.11/checkstyle-8.11-all.jar"
CHECKSTYLE_JAR=".checkstyle.jar"
CHECKSTYLE_CONFIG="pepper-apis/checkstyle.xml"

function get_checkstyle_jar() {
    local curl_path=$(which curl 2>/dev/null)
    local wget_path=$(which wget 2>/dev/null)
    if [[ -n "${curl_path}" ]]; then
        "${curl_path}" \
            -sL \
            -o "${CHECKSTYLE_JAR}" \
            "${CHECKSTYLE_URL}"
    elif [[ -n "${wget_path}" ]]; then 
        "${wget_path}" \
            -o "${CHECKSTYLE_JAR}" \
            "${CHECKSTYLE_URL}"
    else
        echo "error: unable to find wget or curl"
        return -1
    fi
}

if [[ ! -f "${CHECKSTYLE_JAR}" ]]; then
    echo "checkstyle not found- fetching"
    get_checkstyle_jar
fi

if git rev-parse --verify HEAD >/dev/null 2>&1; then
    against=HEAD
else
    # Initial commit: diff against an empty tree object
    against=$(git hash-object -t tree /dev/null)
fi

IFS=$'\n'
changed_files=($(git diff --cached --name-only --diff-filter=ACM ${against}))
unset IFS

java_files=()
for file in ${changed_files[@]}; do
    case "${file}" in
    *.java )
        java_files+=("${file}")
        ;;
    *)
        ;;
    esac
done

java \
    -jar "${CHECKSTYLE_JAR}" \
    -c "${CHECKSTYLE_CONFIG}" \
    $( IFS=' '; echo "${java_files[*]}" )