module BenchmarkDriver

def with_clean_env(&block)
  # chruby sets GEM_HOME and GEM_PATH in your shell. We have to unset it in the child
  # process to avoid installing gems to the version that is running benchmark-driver.
  env = nil
  ['GEM_HOME', 'GEM_PATH'].each do |var|
    if ENV.key?(var)
      env ||= ENV.to_h
      ENV.delete(var)
    end
  end
  unless defined?(Gem::Version)
    # default-gem Bundler can be loaded and broken with --disable-gems
    return block.call
  end
  require 'bundler'
  if Bundler.respond_to?(:with_unbundled_env)
    Bundler.with_unbundled_env do
      block.call
    end
  else
    Bundler.with_clean_env do
      block.call
    end
  end
rescue LoadError
  block.call
ensure
  if env
    ENV.replace(env)
  end
end