Rake task to build rdoc exactly as `gem install` would

gistfile1.rb

# I've folded this idea into http://github.com/matthewtodd/shoe
# See what you think!

require 'rubygems'
require 'rubygems/doc_manager'

spec = Gem::Specification.new do |spec|
  # ...
end

desc 'Generate documentation'
task :rdoc do
  def spec.full_gem_path
    File.dirname(__FILE__)
  end
  
  klass = Class.new(Gem::DocManager) do
    def initialize(spec)
      @spec      = spec
      @doc_dir   = File.dirname(__FILE__)
      @rdoc_args = []
    end
  end
  
  klass.new(spec).generate_rdoc
end

desc 'Generate a gemspec file'
task :gemspec do
  File.open("#{spec.name}.gemspec", 'w') do |f|
    f.write spec.to_ruby
  end
end