Custom fnm env

custom-fnm-env.zsh

if type fnm > /dev/null; then
    export FNM_MULTISHELL_ROOT="/run/user/$UID/fnm_multishells"
    export FNM_LOGLEVEL="info"
    export FNM_VERSION_FILE_STRATEGY="local"
    export FNM_MULTISHELL_PATH="$FNM_MULTISHELL_ROOT/$$"
    export FNM_COREPACK_ENABLED="false"
    export FNM_DIR="$HOME/.local/share/fnm"
    export FNM_ARCH="x64"
    export FNM_RESOLVE_ENGINES="false"
    export FNM_NODE_DIST_MIRROR="https://nodejs.org/dist"

    export PATH="$FNM_MULTISHELL_PATH/bin":$PATH

    autoload -U add-zsh-hook
    _fnm_on_exit () {{
        rm -f "$FNM_MULTISHELL_PATH"
    }}
    add-zsh-hook zshexit _fnm_on_exit && _fnm_on_exit

    mkdir -p "$FNM_MULTISHELL_ROOT"

    ln -s "$FNM_DIR/aliases/default" "$FNM_MULTISHELL_PATH"
    rehash

    _fnm_autoload_hook () {{
        if [[ -f .node-version || -f .nvmrc ]]; then
            fnm use --silent-if-unchanged
        fi
    }}
    add-zsh-hook chpwd _fnm_autoload_hook
fi

This is my customized setup in .zshrc for fnm, which is a much faster alternative to nvm for managing multiple node installs.

Key changes to output from fnm env:

1. I'm using the current pid of the shell for the symlink path instead of the pid of the fnm process when generating the env commands. This is easier to reason about, and it allows me to query ps -p <pid> to detect dangling links.
2. I added a zshexit hook to remove the symlink when the shell exits. Taken from the experimental branch in fnm here.
3. Added back in the --use-on-cd option effect.

I skip all of this if fnm is not installed.