Tip: `fnm` & `volta` setup

[mrienstra]

If you wish to use both volta and fnm, with fnm as the default, the following setup is working so far, though I just put it together, so who knows! (details are specific to macOS / ZSH):

1. Make sure you don't run volta install node, so volta has no global version of node installed. Then volta will fall-through to fnm, if you're not in a directory with volta in package.json.
2. The volta installer adds two lines to ~/.zshenv -- leave those there so that Volta will be used by non-interactive tools, e.g. for linting.
3. Copy the volta lines from ~/.zshenv and put them in your ~/.zshrc, after fnm, to make sure volta is in your path before fnm -- in my case, that looks like the following:

eval "$(fnm env --use-on-cd)"

# Volta, copied from `.zshenv` (where it remains), to ensure it takes precedence over `fnm`
export VOLTA_HOME="$HOME/.volta"
export PATH="$VOLTA_HOME/bin:$PATH"

4. One downside, especially if (when) you forget about this arrangement: which node will return something like ~/.volta/bin/node (rather than ~/.local/state/fnm_multishells/65437_1748363068373/bin/node), even when fnm is actually providing node. You can give "future you" a clue by adding this to your ~/.zshrc:

if [[ $- == *i* && -t 1 ]]; then
  autoload -U colors && colors
  which() {
    if [[ "$1" == "node" || "$1" == "npm" || "$1" == "yarn" || "$1" == "pnpm" ]]; then
      if [[ -z "${fg[green]}" || -n "$NO_COLOR" ]]; then
        echo "💡To locate the actual binary: 'volta which $1'" >&2
      else
        echo "💡To locate the actual binary: ${bold_color}${fg[green]}volta which $1${reset_color}" >&2
      fi
    fi
    command which "$@"
  }
fi

(I posted the same comment in the fnm repo, figured it might be useful to others)