require 'action_view'
require 'action_controller/mime' # for Rails 2

render :file=>'foo.html.erb', :locals=>{:user=>User.first}
render :file=>'lib/data_feed.xml.builder', :type=>:rxml, :locals=>{:user=>User.first)

def render(options)
  klass = Class.new(ActionView::Base)
  klass.class_eval{ def url_for(x);x;end } # to be able to use link_to
  klass.new.render(options)
end

Insert all the helpers you want and “go!”.strip_tags.auto_link.truncate(25)

# ActionView text helpers
# https://grosser.it/2009/05/30/all-actionview-helpers-on-strings/
class String
  %w[auto_link excerpt highlight sanitize simple_format strip_tags word_wrap].each do |method|
    define_method method do |*args|
      ActionController::Base.helpers.send method, self, *args
    end
  end

  # called with a number or with :length=>10
  def truncate(*args)
    if args.first.is_a?(Hash)
      ActionController::Base.helpers.truncate(self, *args)
    else
      ActionController::Base.helpers.truncate(self, :length=>args[0])
    end
  end
end

polymorphic_path(A::B::User) != users_url
which normally would not be a problem, only that polymorphic_path is used in all form_for / link_to etc helpers…

The simpeles solution i found is overwriting User.model_name with:

def self.model_name
  ActiveSupport::ModelName.new('User')
end