Bundler could not find compatible versions for gem, updating Rails app

Question

After createing a brand new rails app Following the official rails blog post, attempting to convert apps to rails 3.2.0.rc2 yields the following

Updated Gemfile to depend on rails ~> 3.2.0.rc2
    gem 'rails', '~>3.2.0.rc2'
Updated Gemfile to depend on sass-rails ~> 3.2.3
    gem 'sass-rails',   '~> 3.2.3'

$ bundle install
Fetching source index for http://rubygems.org/
Bundler could not find compatible versions for gem "activesupport":
  In snapshot (Gemfile.lock):
    activesupport (3.1.1)

  In Gemfile:
    rails (~> 3.2.0.rc2) ruby depends on
      activesupport (= 3.2.0.rc2) ruby

Running `bundle update` will rebuild your snapshot from scratch, using 
only the gems in your Gemfile, which may resolve the conflict.

$bundle update
Fetching source index for http://rubygems.org/
Bundler could not find compatible versions for gem "railties":
  In Gemfile:
    coffee-rails (~> 3.1.1) ruby depends on
      railties (~> 3.1.0) ruby

    rails (~> 3.2.0.rc2) ruby depends on
      railties (3.2.0.rc2)

What exactly is the issue?

System Specs:

Mac OS 10.7.2, Xcode 4.2.1, rvm 1.10.1 using ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin11.2.0]

Answer 1

I solved it by deleting the lock rm Gemfile.lock and again running bundle install:

$ rm Gemfile.lock
$ bundle install
Using rake (0.9.2.2) 
Using i18n (0.6.0) 
Using multi_json (1.0.4) 
Using activesupport (3.2.0.rc2) 
Using builder (3.0.0) 
Using activemodel (3.2.0.rc2) 
Using erubis (2.7.0) 
Using journey (1.0.0) 
Using rack (1.4.0) 
Using rack-cache (1.1) 
Using rack-test (0.6.1) 
Using hike (1.2.1) 
Using tilt (1.3.3) 
Using sprockets (2.1.2) 
Using actionpack (3.2.0.rc2) 
Using mime-types (1.17.2) 
Using polyglot (0.3.3) 
Using treetop (1.4.10) 
Using mail (2.3.0) 
Using actionmailer (3.2.0.rc2) 
Using arel (3.0.0) 
Using tzinfo (0.3.31) 
Using activerecord (3.2.0.rc2) 
Using activeresource (3.2.0.rc2) 
Using bundler (1.0.21) 
Using coffee-script-source (1.2.0) 
Using execjs (1.2.13) 
Using coffee-script (2.2.0) 
Using rack-ssl (1.3.2) 
Using json (1.6.4) 
Using rdoc (3.12) 
Using thor (0.14.6) 
Using railties (3.2.0.rc2) 
Using coffee-rails (3.2.1) 
Using jquery-rails (2.0.0) 
Using rails (3.2.0.rc2) 
Using sass (3.1.12) 
Using sass-rails (3.2.3) 
Using sqlite3 (1.3.5) 
Using uglifier (1.2.2) 
Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.

This is a pretty brute force way of fixing the issue. If this is an established project, you may run into other issues after deleting the Gemfile.lock as the dependency versions are no longer locked. However, if this is a new project it's unlikely you will run into problems taking this approach.