execute

# File lib/rubygems/commands/pristine_command.rb, line 83
  def execute
    specs = if options[:all] then
              Gem::Specification.map

            # `--extensions` must be explicitly given to pristine only gems
            # with extensions.
            elsif options[:extensions_set] and
                  options[:extensions] and options[:args].empty? then
              Gem::Specification.select do |spec|
                spec.extensions and not spec.extensions.empty?
              end
            else
              get_all_gem_names.sort.map do |gem_name|
                Gem::Specification.find_all_by_name(gem_name, options[:version]).reverse
              end.flatten
            end

    if specs.to_a.empty? then
      raise Gem::Exception,
            "Failed to find gems #{options[:args]} #{options[:version]}"
    end

    install_dir = Gem.dir # TODO use installer option

    raise Gem::FilePermissionError.new(install_dir) unless
      File.writable?(install_dir)

    say "Restoring gems to pristine condition..."

    specs.each do |spec|
      if spec.default_gem?
        say "Skipped #{spec.full_name}, it is a default gem"
        next
      end

      if spec.name == options[:skip]
        say "Skipped #{spec.full_name}, it was given through options"
        next
      end

      if spec.bundled_gem_in_old_ruby?
        say "Skipped #{spec.full_name}, it is bundled with old Ruby"
        next
      end

      unless spec.extensions.empty? or options[:extensions] or options[:only_executables] then
        say "Skipped #{spec.full_name}, it needs to compile an extension"
        next
      end

      gem = spec.cache_file

      unless File.exist? gem or options[:only_executables] then
        require 'rubygems/remote_fetcher'

        say "Cached gem for #{spec.full_name} not found, attempting to fetch..."

        dep = Gem::Dependency.new spec.name, spec.version
        found, _ = Gem::SpecFetcher.fetcher.spec_for_dependency dep

        if found.empty?
          say "Skipped #{spec.full_name}, it was not found from cache and remote sources"
          next
        end

        spec_candidate, source = found.first
        Gem::RemoteFetcher.fetcher.download spec_candidate, source.uri.to_s, spec.base_dir
      end

      env_shebang =
        if options.include? :env_shebang then
          options[:env_shebang]
        else
          install_defaults = Gem::ConfigFile::PLATFORM_DEFAULTS['install']
          install_defaults.to_s['--env-shebang']
        end

      installer_options = {
        :wrappers => true,
        :force => true,
        :install_dir => spec.base_dir,
        :env_shebang => env_shebang,
        :build_args => spec.build_args,
      }

      if options[:only_executables] then
        installer = Gem::Installer.for_spec(spec, installer_options)
        installer.generate_bin
      else
        installer = Gem::Installer.at(gem, installer_options)
        installer.install
      end

      say "Restored #{spec.full_name}"
    end
  end