class ChefCLI::PolicyfileCompiler

def handle_included_policies_preferred_cookbook_conflicts(included_policies_source)
  # All cookbooks in the included policies are preferred.
  conflicting_source_messages = []
  dsl.default_source.reject(&:null?).each do |source_b|
    conflicting_preferences = included_policies_source.preferred_cookbooks & source_b.preferred_cookbooks
    next if conflicting_preferences.empty?
    next if conflicting_preferences.all? do |cookbook_name|
      version = included_policies_source.universe_graph[cookbook_name].keys.first
      if included_policies_source.source_options_for(cookbook_name, version) == source_b.source_options_for(cookbook_name, version)
        true
      else
        false
      end
    end
    conflicting_source_messages << "#{source_b.desc} sets a preferred for cookbook(s) #{conflicting_preferences.join(", ")}. This conflicts with an included policy."
  end
  unless conflicting_source_messages.empty?
    msg = "You may not override the cookbook sources for any cookbooks required by included policies.\n"
    msg << conflicting_source_messages.join("\n") << "\n"
    raise IncludePolicyCookbookSourceConflict.new(msg)
  end
end