ruby on rails - Bundler: You are trying to install in deployment mode after changing your Gemfile

Question

I'm pretty new to bundler and capistrano, and I'm trying to use them together. When I try to deploy, I get the message:

You are trying to install in deployment mode after changing your Gemfile. Run `bundle install' elsewhere and add the updated Gemfile.lock to version control.

I don't know how to satisfy the system that's complaining, and I don't understand why the complaint is coming up because I read in the doc:

If a Gemfile.lock does exist, and you have updated your Gemfile(5), bundler will use the dependencies in the Gemfile.lock for all gems that you did not update, but will re-resolve the dependencies of gems that you did update. You can find more information about this update process below under CONSERVATIVE UPDATING.

I interpret that to mean that the Bundler can handle the fact that my Gemfile is not whatever it expected. Any help?

Specs: Ruby 1.9.3, Rails 3.2.3, Capistrano 2.12.0, Bundler 1.1.4, Windows 7, deploying to a Posix machine.

Edit: My Gemfile includes logic blocks like the following:

unless RbConfig::CONFIG['host_os'] === 'mingw32'
  # gem 'a' ...
end

Answer 1

The error message you're getting regarding Gemfile.lock may be because your Gemfile and Gemfile.lock don't agree with each other. It sounds like you've changed something in your Gemfile since you last ran bundle install (or update). When you bundle install, it updates your Gemfile.lock with any changes you've made to Gemfile.

Make sure you run bundle install locally, and check-in to source control your newly updated Gemfile.lock after that. Then try deploying.

Edit: As recognised in the comments, a conditional in the Gemfile resulted in a valid Gemfile.lock on one platform, invalid on another. Providing a :platform flag for these platform-dependent gems in the Gemfile should solve the asymmetry.