How do I specify different versions of a gem for development and production

Question

I need to have different versions of a gem for development and production, so I put the following in my gemfile.

group :development, :test do
  gem 'rspec-rails', '2.11.0'
  gem 'bcrypt-ruby', '3.1.2'
end

group :production do
  gem 'rails_12factor'
  gem 'bcrypt-ruby', '3.0.1'  
end

but if i try to do bundle install or even just rails console I get the above error

I have tried

bundle install --without production

but I still get the error message. FYI: I need to do this because I am going thru the rails tutorial and there is a conflict that arises between windows, ruby 2.0.0 and bcrypt and Heroku so I am using bcrypt 3.1.2 on windows (with a modification to the active record gemfile) and bcrypt 3.0.1 on Heroku.

See this for more details: Issues using bcrypt 3.0.1 with ruby2.0 on Windows

I basically did what is mentioned in the first answer

EDIT

###################################################################

As the answer below points out, I really should be using the same version in both production and development (even tho I am just working thur a tutorial). What I ended up doing is monkey patching ActiveModel to use

gem 'bcrypt-ruby', '3.1.2'

rather than

gem 'bcrypt-ruby', '~> 3.0.0'

in secure_password.

I accomplished this by placing the following in lib/secure_password_using_3_1_2.rb

module ActiveModel
  module SecurePassword
    extend ActiveSupport::Concern

    module ClassMethods

      def has_secure_password
        # Load bcrypt-ruby only when has_secure_password is used.
        # This is to avoid ActiveModel (and by extension the entire framework) being dependent on a binary library.
        #gem 'bcrypt-ruby', '~> 3.0.0'
        gem 'bcrypt-ruby', '3.1.2'
        require 'bcrypt'

        attr_reader :password

        validates_confirmation_of :password
        validates_presence_of     :password_digest

        include InstanceMethodsOnActivation

        if respond_to?(:attributes_protected_by_default)
          def self.attributes_protected_by_default
            super + ['password_digest']
          end
        end
      end
    end
  end
end

and then adding the following to config/environment.rb

require File.expand_path('../../lib/secure_password_using_3_1_2.rb', __FILE__)

Answer 1

How about this?

gem "my_gem", ENV["RAILS_ENV"] == "production" ? "2.0" : "1.0"

RAILS_ENV=production bundle