nixpkgs/pkgs/development/interpreters/lua-5/setup-hook.sh

# set -e

nix_print() {
  if [ ${NIX_DEBUG:-0} -ge $1 ]; then
    echo "$2"
  fi
}

nix_debug() {
  nix_print 3 "$1"
}

addToLuaSearchPathWithCustomDelimiter() {
  local varName="$1"
  local absPattern="$2"
  # delete longest match starting from the lua placeholder '?'
  local topDir="${absPattern%%\?*}"

  # export only if the folder exists else LUA_PATH/LUA_CPATH grow too large
  if [[ ! -d "$topDir" ]]; then return; fi

  # export only if we haven't already got this dir in the search path
  if [[ ${!varName-} == *"$absPattern"* ]]; then return; fi

  export "${varName}=${!varName:+${!varName};}${absPattern}"
}

addToLuaPath() {
  local dir="$1"

  if [[ ! -d "$dir" ]]; then
    nix_debug "$dir not a directory abort"
    return 0
  fi
  cd "$dir"
  for pattern in @luapathsearchpaths@; do
    addToLuaSearchPathWithCustomDelimiter LUA_PATH "$PWD/$pattern"
  done

  # LUA_CPATH
  for pattern in @luacpathsearchpaths@; do
    addToLuaSearchPathWithCustomDelimiter LUA_CPATH "$PWD/$pattern"
  done
  cd - >/dev/null
}

addEnvHooks "$hostOffset" addToLuaPath