install

# File lib/rubygems/dependency_installer.rb, line 387
  def install dep_or_name, version = Gem::Requirement.default
    request_set = resolve_dependencies dep_or_name, version

    @installed_gems = []

    options = {
      :bin_dir             => @bin_dir,
      :build_args          => @build_args,
      :document            => @document,
      :env_shebang         => @env_shebang,
      :force               => @force,
      :format_executable   => @format_executable,
      :ignore_dependencies => @ignore_dependencies,
      :prerelease          => @prerelease,
      :security_policy     => @security_policy,
      :user_install        => @user_install,
      :wrappers            => @wrappers,
      :build_root          => @build_root,
      :install_as_default  => @install_as_default
    }
    options[:install_dir] = @install_dir if @only_install_dir

    request_set.install options do |_, installer|
      @installed_gems << installer.spec if installer
    end

    @installed_gems.sort!

    # Since this is currently only called for docs, we can be lazy and just say
    # it's documentation. Ideally the hook adder could decide whether to be in
    # the background or not, and what to call it.
    in_background "Installing documentation" do
      Gem.done_installing_hooks.each do |hook|
        hook.call self, @installed_gems
      end
    end unless Gem.done_installing_hooks.empty?

    @installed_gems
  end