Responding to my last post, Josh pointed out what should probably be obvious: It's likely a bad idea to bundle bundler. There's a potential for version conflicts.

For our second attempt, we're

As a second attempt, we're now cribbing from the continuous integration setup from the Rails project. So far, so good:

Our RAILS_ROOT/cruise_config.rb...

require 'fileutils'

Project.configure do |project|
  project.build_command = 'sudo gem update --system && ruby lib/cruise/build.rb'
end

And, the referenced lib/cruise/build.rb (the important parts)...

#!/usr/bin/env ruby
require 'fileutils'
include FileUtils

def root_dir
    @root_dir ||= File.expand_path(File.dirname(__FILE__) + '/../..')
end

def rake(*tasks)
  tasks.each { |task| return false unless system("#{root_dir}/bin/rake", task, 'RAILS_ENV=test')}
end

build_results = {}

cd root_dir do
  build_results[:bundle] = system 'gem bundle'  # bundling here, rather than in a task (not in Rails context)
  build_results[:spec] = rake 'cruise:spec'
end

failures = build_results.select { |key, value| value == false }

if failures.empty?
  exit(0)
else
  exit(-1)
end

Thanks go to

• Josh Susser for help via email
• John Pignata for suggesting we look at the Rails project
• Rails team for the reference scripts

More comments and suggestions are encouraged.

On a current project, we've just switched from GemInstaller to Bundler for managing our application's gems.

All in all, the transition was painless... in our development environments. Of course, in order to keep things on running smoothly on the continuous integration box, we amended our rake cruise:spec task to start by running sh "gem bundle".

So, wonderful! Any changes to our gem dependency list will picked up when cruise starts and made available for that "build"; there's no need to log in and make any manual updates. Right?

Not quite. We're using the disable_system_gems option and, in that case, Bundler (very intentionally) modifies your GEM_PATH such that only "vendor'd" gems are available to the application. Which of course means that Bundler itself, being "a gem to bundle gems", is unavailable when that sh "gem bundle" command is run.

Our solution: bundle Bundler, obviously! That's right, in our Bundler Gemfile we've included gem "bundler". Now, after a single manual execution of gem bundle to pick up the bundled Gem Bundler gem bundle (heh), any subsequent Gemfile changes (to gems other than Bundler) get picked up at the start of the build... and we're cruisin'

Have another solution? Please let us know in the comments.