auto-invoke-nvm.sh

# Automatically call `nvm use`/`nvm install` after `cd` or `git checkout` to use
# the version of Node.js defined in .nvmrc (or the default Node.js version if
# there is no .nvmrc and you are in a directory with a package.json file).

# This first `nvm_after_cd` function is based on the function recommended in the
# official documentation at
# https://github.com/nvm-sh/nvm/tree/2c0c34f10e6f415d1c6f60c54fcbf53a7670dec6#bash,
# but avoids calling `nvm` when there is no package.json present so that `cd` is
# not so slow all the time. 

# Only calls nvm when:
# 1) A directory or one of its parents contains a .nvmrc file. In this case,
#    will call `nvm use` or `nvm install`, whichever is appropriate.
# 2) A directory or one of its parents does NOT contain a .nvmrc file AND the
#    directory contains a package.json file, indicating the directory is for a
#    Node.js project. In this case, will call `nvm use default`.
nvm_after_cd() {
    command cd "$@";
    nvm_path=$(nvm_find_up .nvmrc | tr -d '\n')

    # If there are no .nvmrc file AND there is a package.json file (indicating
    # we are in a Node.js project directory), use the default nvm version
    if [[ ! $nvm_path = *[^[:space:]]* && -s package.json ]]; then

        echo "HEY! You should probably create an .nvmrc file for this directory!"
        echo "Like this:"
        echo "  node -v > .nvmrc"
        
        declare default_version;
        default_version=$(nvm version default);

        # If there is no default version, set it to `node`
        # This will use the latest version on your machine
        if [[ $default_version == "N/A" ]]; then
            nvm alias default node;
            default_version=$(nvm version default);
        fi

        # If the current version is not the default version, set it to use the default version
        if [[ $(nvm current) != "$default_version" ]]; then
            nvm use default;
        fi

    elif [[ -s $nvm_path/.nvmrc && -r $nvm_path/.nvmrc ]]; then
        declare nvm_version
        nvm_version=$(<"$nvm_path"/.nvmrc)

        declare locally_resolved_nvm_version
        # `nvm ls` will check all locally-available versions
        # If there are multiple matching versions, take the latest one
        # Remove the `->` and `*` characters and spaces
        # `locally_resolved_nvm_version` will be `N/A` if no local versions are found
        locally_resolved_nvm_version=$(nvm ls --no-colors "$nvm_version" | tail -1 | tr -d '\->*' | tr -d '[:space:]')

        # If it is not already installed, install it
        # `nvm install` will implicitly use the newly-installed version
        if [[ "$locally_resolved_nvm_version" == "N/A" ]]; then
            nvm install "$nvm_version";
        elif [[ $(nvm current) != "$locally_resolved_nvm_version" ]]; then
            nvm use "$nvm_version";
        fi
    fi
}
alias cd='nvm_after_cd'
cd "$PWD"

# Automatically set the Node.js version defined in .nvmrc after a git checkout
# by invoking `cd .`. Depends on auto-invoke-nvm-on-cd.sh.
cd_dot_after_git_checkout() {
    if [[ $1 == "checkout" ]]; then
      command git "$@" && cd .
    else
      command git "$@"
    fi
}
alias git='cd_dot_after_git_checkout'