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