unpacking/freezing gems into a non-rails ruby app

Question

I'm writing a non-Rails ruby application (gasp!) and would like to be able to include all the gem dependencies which the application requires in a vendor subdirectory. This would be similar to how http://gemsonrails.rubyforge.org/ works for Rails apps.

The goal here is to avoid the situation my team currently experiences when a new dependency is added. Every developer on my team has to install the gem manually, and then someone has to manually update each test and staging and production machine. If we can freeze the dependencies into the distributed application itself then a simple svn update (or git pull for those hipsters in the crowd) would be all that is needed.

Answer 1

UPDATE (New Solution):

Try Yehuda Katz's new bundler gem. gem install bundler then create a Gemfile with all your dependencies. See the documentation for more info.

Old Recommendation:

One easy way is to just manually unpack the gems into your vendor directory and add the lib path of the unpacked gems to the front of the $LOAD_PATH.

To unpack a gem:

$ cd vendor/gems
$ gem unpack active_support
Unpacked gem: '/path/to/myproject/vendor/gems/activesupport-2.3.2'

Just make sure you unpack all the necessary gems and their dependencies (using the correct versions).

To add all gems under vendor/gems to your $LOAD_PATH, try adding something like this to your application's initialization:

Dir.glob(File.join("vendor", "gems", "*", "lib")).each do |lib|
  $LOAD_PATH.unshift(File.expand_path(lib))
end

Update: Sarah (in the comments) convinced me it might also be necessary to override the GEM_PATH. Here's one way to do that:

require 'rubygems'
gem_paths = [File.expand_path(File.join("vendor", "gems")),  Gem.default_dir]
Gem.clear_paths
Gem.send :set_paths, gem_paths.join(":")

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Another option is to look into Rip (Ruby’s Intelligent Packaging) for managing your dependencies. Rip looks really sweet, but it's still new.