Check last built date of gems in your Gemfile to find out how old is the most recent gem version.

gem_maintanability_check.rb

def check_for_old_dependencies
  outdated_gems = list_gems
  parsed_gems   = parse_outdated_gems outdated_gems
  results       = check_age parsed_gems
  ordered       = results.sort_by { |gem| gem[1] }
  File.open('results.json', 'w') { |f| f.write JSON.dump(ordered) }
  print_results ordered
end

def list_gems
  puts "Running 'bundle outdated'\n"
  
  `bundle outdated --parseable --only-explicit`
end

def parse_outdated_gems(raw)
  raw.split("\n").reject(&:empty?).map do |line|
    gem = line.split(' ')
    { gem_name: gem[0], gem_newest_version: gem[2].gsub(',', '') }
  end
end

def print_results(gems)
  puts "Outdated gems sorted by date of their last built\n"
  gems.each { |gem| puts "#{gem[:gem_name]}: #{gem[:gem_last_built]}"}
end

def check_age(gems)
  puts "Getting latest gem versions @ rubygems.org\n"

  results = gems.map do |gem|
    url = URI.parse("https://rubygems.org/api/v2/rubygems/#{gem[:gem_name]}/versions/#{gem[:gem_newest_version]}.json")
    res = Net::HTTP.get_response url
    parsed = JSON.parse res.body
    { gem_name: gem[:gem_name], gem_last_built: parsed['built_at'], gem_newest_version: gem[:gem_newest_version] }
  end
end

check_for_old_dependencies