fetch_spec

# File lib/rubygems/spec_fetcher.rb, line 105
  def fetch_spec(spec, source_uri)
    source_uri = URI.parse source_uri if String === source_uri
    spec = spec - [nil, 'ruby', '']
    spec_file_name = "#{spec.join '-'}.gemspec"

    uri = source_uri + "#{Gem::MARSHAL_SPEC_DIR}#{spec_file_name}"

    cache_dir = cache_dir uri

    local_spec = File.join cache_dir, spec_file_name

    if File.exist? local_spec then
      spec = Gem.read_binary local_spec
    else
      uri.path << '.rz'

      spec = @fetcher.fetch_path uri
      spec = Gem.inflate spec

      if @update_cache then
        FileUtils.mkdir_p cache_dir

        open local_spec, 'wb' do |io|
          io.write spec
        end
      end
    end

    # TODO: Investigate setting Gem::Specification#loaded_from to a URI
    Marshal.load spec
  end