ZSH function to auto-switch to correct Node version

.zshrc

####
# ZSH function to auto-switch to correct Node version
#   https://gist.github.com/callumlocke/30990e247e52ab6ac1aa98e5f0e5bbf5
#
# - Searches up your directory tree for the closest .nvmrc, just like `nvm use` does.
#
# - If you are already on the right Node version, IT DOES NOTHING, AND PRINTS NOTHING.
#
# - Works correctly if your .nvmrc file contains something relaxed/generic,
#   like "4" or "v12.0" or "stable".
#
# - If an .nvmrc is found but you have no installed version that satisfies it, it
#   prints a clear warning, so you can decide whether you want to run `nvm install`.
#
# - If no .nvmrc is found, it does `nvm use default`.
# 
# Recommended: leave your default as something generic,
# e.g. do `nvm alias default stable`
####

auto-switch-node-version() {
  NVMRC_PATH=$(nvm_find_nvmrc)
  CURRENT_NODE_VERSION=$(nvm version)

  if [[ ! -z "$NVMRC_PATH" ]]; then
    # .nvmrc file found!

    # Read the file
    REQUESTED_NODE_VERSION=$(cat $NVMRC_PATH)

    # Find an installed Node version that satisfies the .nvmrc
    MATCHED_NODE_VERSION=$(nvm_match_version $REQUESTED_NODE_VERSION)

    if [[ ! -z "$MATCHED_NODE_VERSION" && $MATCHED_NODE_VERSION != "N/A" ]]; then
      # A suitable version is already installed.

      # Clear any warning suppression
      unset AUTOSWITCH_NODE_SUPPRESS_WARNING

      # Switch to the matched version ONLY if necessary
      if [[ $CURRENT_NODE_VERSION != $MATCHED_NODE_VERSION ]]; then
        nvm use $REQUESTED_NODE_VERSION
      fi
    else
      # No installed Node version satisfies the .nvmrc.

      # Quit silently if we already just warned about this exact .nvmrc file, so you
      # only get spammed once while navigating around within a single project.
      if [[ $AUTOSWITCH_NODE_SUPPRESS_WARNING == $NVMRC_PATH ]]; then
        return
      fi

      # Convert the .nvmrc path to a relative one (if possible) for readability
      RELATIVE_NVMRC_PATH="$(realpath --relative-to=$(pwd) $NVMRC_PATH 2> /dev/null || echo $NVMRC_PATH)"

      # Print a clear warning message
      echo ""
      echo "WARNING"
      echo "  Found file: $RELATIVE_NVMRC_PATH"
      echo "  specifying: $REQUESTED_NODE_VERSION"
      echo "  ...but no installed Node version satisfies this."
      echo "  "
      echo "  Current node version: $CURRENT_NODE_VERSION"
      echo "  "
      echo "  You might want to run \"nvm install\""

      # Record that we already warned about this unsatisfiable .nvmrc file
      export AUTOSWITCH_NODE_SUPPRESS_WARNING=$NVMRC_PATH
    fi
  else
    # No .nvmrc file found.

    # Clear any warning suppression
    unset AUTOSWITCH_NODE_SUPPRESS_WARNING

    # Revert to default version, unless that's already the current version.
    if [[ $CURRENT_NODE_VERSION != $(nvm version default)  ]]; then
      nvm use default
    fi
  fi
}

# Run the above function in ZSH whenever you change directory
autoload -U add-zsh-hook
add-zsh-hook chpwd auto-switch-node-version
auto-switch-node-version

Awesome script! Thank you!

Is anyone using the avn + avn-nvm packages? How does this compare? I think it supports .nvmrc too.

FYI avn is no longer maintained.

It's also worth mentioning to that add-zsh-hook chpwd auto-switch-node-version should be added to your .zshrc file. I was under the assumption that a “hook” was persistent between terminal sessions, and I couldn't work out why it stopped working after quitting my terminal. So make sure to run it every time your terminal window opens.

@callumlocke terrific job. Thank! 👏 👏 👏

I want to add some notes:

---

Adding the source causes lazy loading of NVM did not to work and can cause performance issues on terminal startup.

DON'T

export NVM_DIR="$([ -z "${XDG_CONFIG_HOME-}" ] && printf %s "${HOME}/.nvm" || printf %s "${XDG_CONFIG_HOME}/nvm")"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"

Instead of that include the minimal code from https://github.dev/nvm-sh/nvm#zsh to avoid the error message.

DO

nvm_echo() {
    command printf %s\\n "$*" 2>/dev/null
}

# Traverse up in directory tree to find containing folder
nvm_find_up() {
    local path_
    path_="${PWD}"
    while [ "${path_}" != "" ] && [ "${path_}" != '.' ] && [ ! -f "${path_}/${1-}" ]; do
        path_=${path_%/*}
    done
    nvm_echo "${path_}"
}

nvm_find_nvmrc() {
    local dir
    dir="$(nvm_find_up '.nvmrc')"
    if [ -e "${dir}/.nvmrc" ]; then
        nvm_echo "${dir}/.nvmrc"
    fi
}

---

I'm also forked it with a version who install the required version instead of showing a warning message:

auto-switch-node-version() {
    local nvmrc_path=$(nvm_find_nvmrc)
    local current_node_version=$(nvm version)

    if [[ ! -z "$nvmrc_path" ]]; then
        # .nvmrc file found!

        # Read the file
        local requested_node_version=$(cat $nvmrc_path)

        # Find an installed Node version that satisfies the .nvmrc
        local matched_node_version=$(nvm_match_version $requested_node_version)

        if [[ ! -z "$matched_node_version" && $matched_node_version != "N/A" ]]; then
            # A suitable version is already installed.

            # Switch to the matched version ONLY if necessary
            if [[ $current_node_version != $matched_node_version ]]; then
                nvm use $requested_node_version
            fi
        else
            # No installed Node version satisfies the .nvmrc.

            if [[-z "$current_node_version"]]; then
                # Install the requested version on the .nvmrc file
                nvm install
            else
                # Install the requested version on the .nvmrc file with the current packages installed
                nvm install --reinstall-packages-from=${current_node_version}
            fi
        fi
    else
        # No .nvmrc file found.

        # Revert to default version, unless that's already the current version.
        if [[ $current_node_version != $(nvm version default)  ]]; then
            nvm use default
        fi
    fi
}