Simple NPM version checker

lib__npm_check.rb

class NpmCheck
  # Checks package.json against the local node_modules directory
  # to assert that every package specified in package.json is
  # present in node_modules. If possible, it performs a basic
  # "newer or equal than" check on the package's version. Without
  # access to npm's semver primitizes & parsing it is a bit more difficult
  # to perform proper version matching checks.
  #
  # Requires https://github.com/jlindsey/semantic to parse versions.
  # 
  # `npm ls` will also do these things .. which I learned after writing this code!
  #
  # Copyright (c) 2016 Marketplacer
  # Licensed under the MIT License https://opensource.org/licenses/MIT

  def initialize package_json_path, node_modules_path: nil
    @package_json_path = package_json_path
    @node_modules_path = node_modules_path
    @node_modules_path ||= File.expand_path('../node_modules', package_json_path)
  end

  def missing_dependencies check_dev_deps: false
    package_json = JSON.parse(File.read(@package_json_path))

    dependencies = package_json['dependencies']
    if check_dev_deps
      dependencies = dependencies.merge(package_json['devDependencies'])
    end

    results = dependencies.map do |name, version|
      check_dep name, version
    end

    results.reject(&:nil?)
  end

  private

  def check_dep name, version
    path = File.join(@node_modules_path, name, 'package.json')

    return "'#{name}' is missing (#{version} required)" if !File.exist?(path)

    version = begin
      Semantic::Version.new(version)
    rescue ArgumentError
      # Not a parseable version, eg 'github:marketplacer/react-dnd-html5-backend',
      # so abort here.
      return nil
    end

    dep_json = JSON.parse(File.read(path))
    package_version = Semantic::Version.new(dep_json['version'])
    if package_version < version
      return "old version of '#{name}' (#{package_version} found < #{version} required)"
    end

    nil
  end
end

script__check_npm_deps.rb

#!/usr/bin/env ruby

require 'bundler/setup'
require_relative '../lib/npm_check'
require 'semantic'
require 'json'

missing = NpmCheck.new(File.expand_path('../../package.json', __FILE__)).missing_dependencies
if missing.length > 0
  $stderr.puts "NPM modules missing or out of date:"
  $stderr.puts
  $stderr.puts missing.map {|m| "  * #{m}"}.join("\n")
  $stderr.puts
  $stderr.puts "Run `npm install` to resolve."
  exit 1
end