Check local environment for Yarn and NVM, and prompt to install if they're missing

env.sh

#!/bin/bash

log_error () {
	echo -e "\x1b[31m$1\x1b[0m"
}

log_info () {
	echo -e "\x1b[2m$1\x1b[0m"
}

log_info 'Checking environment'

# make sure yarn is installed, and that it supports `policies`
# https://classic.yarnpkg.com/en/docs/cli/policies/
# https://github.com/yarnpkg/yarn/releases/tag/v1.13.0

if ! [ -x "$(command -v yarn)" ]; then
	log_error "Could not find Yarn. Please install it before continuing:"
	log_info "https://classic.yarnpkg.com/en/docs/install"
else
	YARN_VERSION=$(yarn --version)
	REQUIRED_VERSION="1.13.0"

	if ! [ "$(printf '%s\n' "$REQUIRED_VERSION" "$YARN_VERSION" | sort -V | head -n1)" = "$REQUIRED_VERSION" ]; then
		log_error "Your version of Yarn is too old (found $YARN_VERSION but wanted $REQUIRED_VERSION or above). Please update it before continuing:"
		log_info "https://classic.yarnpkg.com/en/docs/install"
	fi
fi

# Check NVM is installed and usable

NVM="$HOME/.nvm/nvm.sh"

if ! [ -f "$NVM" ] || ! source $NVM || ! [ "$(command -v nvm)" ] ; then
	log_error "Could not find NVM. Please install it before continuing:"
	log_info "https://github.com/creationix/nvm#installation-and-update"
fi