Why would yaml be unavailable in production?

Question

On my OS X development system:

$ ruby --version
ruby 1.8.6 (2007-03-13 patchlevel 0) [universal-darwin8.0]

$ script/console
Loading development environment (Rails 2.3.4)
>> require 'yaml'
=> []

On CentOS 5.3 production system:

$ script/console production
Loading production environment (Rails 2.3.4)
/opt/ruby-enterprise-1.8.7-2009.10/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/base.rb:1959:in `method_missing':NoMethodError: undefined method `define_index' for #<Class:0x2e6f7b0>
>> require 'yaml'
=> false

Anything I can do about that NoMethodError?

Why would yaml be unavailable. Isn't it part of the core Ruby libraries?

Answer 1

It is part of the Ruby core libraries, but I'm not sure what gets bundled up with Ruby Enterprise Edition. Check that yaml.rb is inside your $LOAD_PATH. For example, try this in irb:

$LOAD_PATH.collect { |path| File.join(path, 'yaml.rb') }.find { |path| File.exist?(path) }

On OS X it will produce something like:

=> "/opt/local/lib/ruby/1.8/yaml.rb"

Answer 2

Returning false means that the loading was successful or was already done. If it couldn't be loaded, it'd raise an exception instead.