Using whatever lib code to modify global config constant in a Ruby on Rails application.rb file

application.rb

# your_rails_app/config/application.rb

# require File.expand_path('../boot', __FILE__)
#
# Pick the frameworks you want:
#require "active_record/railtie"
#
# [...]


# require whatever lib code
require "#{File.expand_path('../../lib/whatever.rb', __FILE__)}"
# create hash from app config file
hash = YAML.load(File.read(File.expand_path('../application.yml', __FILE__)))
# overwrite top level vars with env specific vars
hash.merge!(hash[Rails.env]||{})
# modify hash with whatever lib code
CONFIG = Whatever.something(hash)


#module YourRailsApp
#  class Application < Rails::Application
#
# [...]