Today I had my first look at rails 3.0.pre and below are the sequence of steps I had to take to create a rails 3.0.pre application, and get it’s generators to work.
Why was I looking at the top-secret, yet open-source Rails 3.0? Their generators are being migrated over to Thor and I wanted to see them in action. I was thinking I might migrate newgem to use Thor too.
Here’s a quick poke around of getting started and interesting things I found. Any hiccups and workarounds are meant as a guide to pre-pre-3.0 users/developers and not as a criticism of rails-core. Rails 3.0 is looking shiny and awesome.
NOTE: Since this is a “how to install and use” rails 3.0 edge, which is still in heavy development, this set of instructions might break. Let’s hope not.
As of today, you cannot install 3.0.pre from rubygems . So, let’s install them from source. Which is handy, you might like to patch something.
$ cd ~/gems $ git clone git://github.com/rails/rails.git use_ruby_191 *
[*] If you are on OS X Snow Leopard I think you can ignore this. Otherwise, since you don’t have the 3.0.pre gems installed, you’re about to hit bump #1. Ruby 1.8.6 doesn’t have
Symbol#to_proc but it’s required to create a rails app. This means you’ll need to be able to switch to another version of ruby temporarily if you’re on ruby 1.8.6 .
cd ~/Sites ruby ~/gems/rails/railties/bin/rails
Oooh, look at all the new options! Some new ones are:
-F, [--freeze] # Freeze Rails in vendor/rails from the gems -O, [--skip-activerecord] # Skip ActiveRecord files -T, [--skip-testunit] # Skip TestUnit files -J, [--skip-prototype] # Skip Prototype files
-D, --with-dispatchers flags have been removed.
--freeze isn’t new, but
So, to create an app, I dutifully used:
ruby ~/gems/rails/railties/bin/rails edgerailsapp -F
BAM! Fail. The -F option to freeze/vendor rails fails without the gems installed. So don’t use it.
ruby ~/gems/rails/railties/bin/rails edgerailsapp ln -s ~/gems/rails vendor/rails
If you’re on Windows without the symlink command
ln, then copy the downloaded rails source into
Fetch Rails’ dependencies
Rails 3.0 source uses the new bundler project to describe its own dependencies. From Nick Quaranto’s article on bundler, get the latest:
cd ~/gems git clone git://github.com/wycats/bundler cd bundler sudo rake install
Now, back in your app, you need to install some rails dependencies here too. It’s a good chance to see how you’ll bundle gem dependencies in the future.
$ cd ~/Sites/edgerailsapp
Gemfile in your project to the following:
gem "rack", "1.0.1" gem "rack-mount", :git => "git://github.com/rails/rack-mount.git" gem "rack-test", "~> 0.5.0" gem "erubis", "~> 2.6.0" gem "arel", :git => "git://github.com/rails/arel.git" gem "sqlite3-ruby" gem "rails", "3.0.pre", :git => "git://github.com/rails/rails.git"
Welcome to the future of gem dependencies for rails apps. Ultimately you won’t need to manually add these lines yourself. When rails is distributed as gems it will automatically install these for you, I assume/hope/guess. But for today, you seem to need them.
Now locally (within your app) install these gems:
$ gem bundle
If you get “can’t convert Pathname into String” then revert to ruby 1.8.X and reinstall bundler into your 1.8 gem cache.
Phew. Ooh, my god. Phew. Only now will
For me, this outputs:
Please select a generator. Builtin: app, controller, generator, helper, integration_test, mailer, metal, migration, model, model_subclass, observer, performance_test, plugin, resource, scaffold, scaffold_controller, session_migration, stylesheets. Others: app_layout:app_layout, check_migration_version:check_migration_version, home_route:home_route.
The “Builtin” generators are the latest and greatest in Thor technology. Rails 3.0 no longer uses its own generator but is built upon Thor.
For example, our old favourite
model generator works thusly:
$ script/generate model Post title:string --no-fixture invoke active_record create db/migrate/20091103030824_create_posts.rb create app/models/post.rb invoke test_unit create test/unit/post_test.rb
--no-fixture isn’t mentioned in the usage information for
script/generate model. It mentions the
--fixture flag, but I had to guess that
--no-fixture was also supported.
Hmm, I want to use rspec. So, let’s destroy these files:
$ script/destroy model Post title:string invoke active_record .../vendor/gems/dirs/rails/railties/lib/rails/generators/active_record.rb:14:in `next_migration_number': uninitialized constant ActiveRecord::Base (NameError)
What if I wanted to run rspec and cucumber generators, for example, against an edge rails app?
Rails 2 generators
The “Others” generators are my own local generators from
~/.rails/generators. Amusingly, instead of
app_layout it is called
app_layout:app_layout. Not surprisingly at all, if I try to run the rails 2 generator it fails:
$ script/generate app_layout:app_layout [WARNING] Could not load generator at "/Users/drnic/.rails/generators/app_layout/app_layout_generator.rb". Error: uninitialized constant Rails::Generator Could not find generator app_layout:app_layout.
Note, I have rspec, rspec-rails and cucumber gems installed locally but I cannot see their rails generators above. Rails 3 doesn’t look for generators in the same way and old Rails 2 generators don’t work anymore.
That’s the news: every rails 2 generator is broken.
Finally, JosÃ© Valim has a sample Rails 3 app with some vendored generators in it.
These are the things I’m researching now.
This article is long, mostly because rails 3.0.pre hasn’t been released as a set of RubyGems. If it had, then all the dependencies would be installed automatically.
It also introduces gem/plugin writers to the first upgrade issue: your current generators are neither discovered nor work by a rails 3.0 app. We’re all clever cookies, so here’s hoping we can figure out the upgrade path and that it’s simple enough to not be the topic of Dan Brown’s next book.
 Two portions of rails 3.0.pre are available as pre-release gems: activesupport (which is now very modularised and only loads up the parts that you require) and activemodel (which is shiny and new and hence completely safe for rails-core to release).
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