rails generate not working with mongoid - ruby-on-rails

Question

I just created an app in rails with mongoid.
When I attempt to follow the tutorial on the mongoid site and run
rails g mongoid:config
I get the following set of errors.
/Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.1.1/lib/active_support/whiny_nil.rb:48:in `method_missing': undefined method `values' for nil:NilClass (NoMethodError)
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/mongoid-2.3.4/lib/mongoid/railtie.rb:64:in `block in <class:Railtie>'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/initializable.rb:30:in `instance_exec'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/initializable.rb:30:in `run'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/initializable.rb:55:in `block in run_initializers'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/initializable.rb:54:in `each'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/initializable.rb:54:in `run_initializers'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/application.rb:96:in `initialize!'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/railtie/configurable.rb:30:in `method_missing'
from /Users/XXXXXX/melodizr/config/environment.rb:5:in `<top (required)>'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/application.rb:83:in `require'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/application.rb:83:in `require_environment!'
from /Users/XXXXXX/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/commands.rb:22:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
Please help, this is killing me, I feel like I'm not missing anything but its late and I'm probably wrong.

Answer 1

What version of rails are you running?
Something is messed up. Make sure you have the latest gems (don't specify versions in your gemfile):
Run all of these in your rails app dir:
gem update --system
gem update
bundle install
bundle update
Now that you are up to date try it again. If it stil barfs, just make the file yourself. All that this generator does is make mongoid.yml in the config directory that looks like this:
development:
host: localhost
database: mongoid_test_development
test:
host: localhost
database: mongoid_test_test
# set these environment variables on your prod server
production:
host: <%= ENV['MONGOID_HOST'] %>
port: <%= ENV['MONGOID_PORT'] %>
username: <%= ENV['MONGOID_USERNAME'] %>
password: <%= ENV['MONGOID_PASSWORD'] %>
database: <%= ENV['MONGOID_DATABASE'] %>
# slaves:
# - host: slave1.local
# port: 27018
# - host: slave2.local
# port: 27019

Answer 2

This exact issue is caused when mongoid.yml is missing the environment section. The docs say do this:
host: localhost
database: my_database
But they assume you've used the generator which REALLY does something like this:
development:
host: localhost
database: my_database
That line in the railtie is parsing the yml file assuming you've got an environment set up. Note the other answer that alludes to this and if you followed the instructions WOULD fix it assuming you force overrode the existing broken mongoid.yml

Answer 3

I have observed this issue when you fail to include the three RAILS_ENV sections in your mongoid.yml. I have found that you MUST include all three sections in mongoid.yml YAML config file as below...
development:
host: foo-bar
.....
test:
host: test-bar
....
production:
host: prod-bar
....

Answer 4

I had to remove, temporarily, the gem spring for it to work. Otherwise the task rails g mongoid:config would not finish executing.