rubigen

Ruby Generator Framework

What

A framework to allow Ruby applications to generate file/folder stubs (like the rails command does for Ruby on Rails, and the ‘script/generate’ command within a Rails application during development).

Background

RubiGen is originally extracted from Ruby on Rails (specifically the rails_generator from its railties gem).

The rails_generator was hardcoded with Rails-specific dependencies (RAILS_ROOT), Rails generators (‘app’ = Rails application; ‘model’ = Rails model+tests+migration), and generally assumed it was the only generator framework within the Ruby world (it was). So, any RubyGem whose name ended with ‘_generator’ was assumed to be a generator for a Rails application.

But if you are developing a Merb application, then you may want a different set of generators. If you are developing a RubyGem, then you will want a different set of generators.

RubiGen exists to give different development environments their own generator framework.

Installing

RubiGen is only required at development time, and normally isn’t required at deployment time (unless your application uses it to generate files etc for its users).

On your development machine:

sudo gem install rubigen

Usage

RubiGen will be normally integrated into another RubyGem, such as newgem or merb or camping, rather than be used on its own.

These frameworks might use RubiGen for two reasons:

1. To generate an initial stub for developers, e.g. rails generated a stub to write a Rails application. newgem generates a stub to write a RubyGem.
   BTW – RubiGen has a builtin application ruby_app which generates a bare-bones Ruby application stub (lib, test, and script folders, plus a Rakefile, and a script/generate script)
2. To generate components within their development areas, e.g. Rails had its script/generate script within each Rails application, which hooked back into the rails_generator to lookup and execute generators.

So, there are two steps to integrating RubiGen into your framework:

1. Use it to generate an initial stub for the developers of your framework. This would create the folders (lib/app, test, script, doc, log, etc) and starting files (Rakefile, README.txt, test/test_helper.rb etc). Importantly, it would generate a script/generate file. The script/generate file (example below) will allow developers of your framework to generate components/extensions within the framework.
   RubiGen allows you to restrict which generators are available. For example, within RubyGem development environment (as generated by newgem), the script/generator only shows rubygem-related generators. Merb could restrict script/generator to only show Merb related generators (or perhaps Merb and/or Rails generators)
2. Your framework RubyGem (e.g. newgem or merb RubyGems) needs to add rubigen as a dependency, so that users of your RubyGem can access the generator framework.

Creating generators

There are two types of generators:

1. Application Generators – used by developers of your framework to get started. Generally, you will create one Application Generator for your framework. It generates a base stub (such as the rails stub for new Rails applications) for your framework users.
2. Component Generators – used by developers to extend their application. You may include 1+ built-in generators with your framework. Developers can also write generators for your framework, and like Rails’ generator install them in various places and have access to their via RubiGen.

Creating an Application Generator for your Framework

Easy way

newgem (v0.13.0+) can generate an Application Generator for a RubyGem.

1. Create new RubyGem: newgem foobar
2. Create generator: script/generator application_generator foobar
3. Update tests + generator
4. Install
5. Run with: foobar

For more documentation, run script/generator application_generator

DIY

Without RubiGen, to give your users a head start and create a stub for them, you will copiously use mkdir_p and File.open. Your script will either be primitive (only create the bare folders and very few files) or it will be very long and unreadable (ok, perhaps I’m just talking about the newgem script, which I am dubiously responsible for… :P).

With RubiGen, you can create stubs using powerful, yet simple, syntax. Templates are extracted into a templates folder, and activating the generator from a script requires only a few lines of code.

These are the newgem files related to its Application Generator.

bin/
  bin/newgem        # Appliction Generator script; Usage: newgem gemname [options]
app_generators/
  app_generators/newgem/
    app_generators/newgem/newgem_generator.rb
    app_generators/newgem/USAGE
    app_generators/newgem/templates/
      app_generators/newgem/templates/app.rb
      app_generators/newgem/templates/History.txt
      app_generators/newgem/templates/... lots and lots of templates

The bin/newgem script is very simple, and looks like:

require 'rubygems'
require 'rubigen'

if %w(-v --version).include? ARGV.first
  require 'newgem/version'
  puts "#{File.basename($0)} #{Newgem::VERSION::STRING}"
  exit(0)
end

require 'rubigen/scripts/generate'
RubiGen::Base.use_application_sources!
RubiGen::Scripts::Generate.new.run(ARGV, :generator => 'newgem')

You can copy and paste this for your own generator script, and place it in your RubyGem’s bin folder. Change newgem to your RubyGem’s name in the script above (and in all the folders listed above too)

NOTE: If you leave newgem there, then it will execute the newgem_generator.rb generator; as the generators are loaded from all RubyGem’s having /app_generators folders.

So, for your RubyGem, you need to keep the /app_generators folder (as you are creating an Application Generator, not a Component Generator), but change newgem to your gem name in all the subfolders and files. ESPECIALLY newgem_generator.rb -> yourgem_generator.rb, as this is how the generator is discovered (via RubiGen::Base.use_application_sources!).

All the generator work is performed within yourgem_generator.rb. A stub for it will be:

require 'rbconfig'

class YourgemGenerator < RubiGen::Base
  DEFAULT_SHEBANG = File.join(Config::CONFIG['bindir'],
                              Config::CONFIG['ruby_install_name'])
                              
  default_options   :shebang => DEFAULT_SHEBANG,
                    :an_option => 'some_default'
  
  attr_reader :app_name, :module_name
  
  def initialize(runtime_args, runtime_options = {})
    super
    usage if args.empty?
    @destination_root = args.shift
    @app_name     = File.basename(File.expand_path(@destination_root))
    @module_name  = app_name.camelize
    extract_options
  end
    
  def manifest
    # Use /usr/bin/env if no special shebang was specified
    script_options     = { :chmod => 0755, :shebang => options[:shebang] == DEFAULT_SHEBANG ? nil : options[:shebang] }
    windows            = (RUBY_PLATFORM =~ /dos|win32|cygwin/i) || (RUBY_PLATFORM =~ /(:?mswin|mingw)/)
    
    record do |m|
      # Root directory and all subdirectories.
      m.directory ''
      BASEDIRS.each { |path| m.directory path }
      
      # Root
      m.template_copy_each %w( Rakefile )
      m.file_copy_each     %w( README.txt )

      # Test helper
      m.template   "test_helper.rb",        "test/test_helper.rb"

      # Scripts
      %w( generate ).each do |file|
        m.template "script/#{file}",        "script/#{file}", script_options
        m.template "script/win_script.cmd", "script/#{file}.cmd", 
          :assigns => { :filename => file } if windows
      end
   
    end
  end

  protected
    def banner
      <<-EOS
Create a stub for #{File.basename $0} to get started.

Usage: #{File.basename $0} /path/to/your/app [options]"
EOS
    end

    def add_options!(opts)
      opts.separator ''
      opts.separator "#{File.basename $0} options:"
      opts.on("-v", "--version", "Show the #{File.basename($0)} version number and quit.")
    end

  # Installation skeleton.  Intermediate directories are automatically
  # created so don't sweat their absence here.
  BASEDIRS = %w(
    doc
    lib
    log
    script
    test
    tmp
  )
end

Easy peasy.

Creating a Component Generator for your Framework

You can include Component Generators in RubyGems, and they will be automatially picked up by your framework’s script/generate script.

Easy way

Use newgem, (v0.13.0+), and run:

script/generate component_generator

and follow the instructions.

Forum

http://groups.google.com/group/rubigen

How to submit patches

Read the 8 steps for fixing other people’s code and for section 8b: Submit patch to Google Groups, use the Google Group above. The trunk repository is svn://rubyforge.org/var/svn/rubigen/trunk for anonymous access.

Thanks go to…

Jeremy Kemper (bitsweat) who wrote the original Rails Generator.

License

This code is free to use under the terms of the MIT license.

Contact

Comments are welcome. Send an email to Dr Nic Williams via the forum

Dr Nic Williams, 22nd August 2007
Theme extended from Paul Battley