# File lib/bundler.rb, line 108
    def setup(*groups)
      # Just return if all groups are already loaded
      return @setup if defined?(@setup)

      definition.validate_ruby!

      if groups.empty?
        # Load all groups, but only once
        @setup = load.setup
      else
        @completed_groups ||= []
        # Figure out which groups haven't been loaded yet
        unloaded = groups - @completed_groups
        # Record groups that are now loaded
        @completed_groups = groups
        unloaded.any? ? load.setup(*groups) : load
      end
    end