ajax_rescues.rb

class ActionController::Base
  private
  
  def rescue_action_in_public(exception)
    respond_to do |want|
      want.html {
        super(exception)
      }
      want.js {
        render :update do |page|
          page.alert "We're sorry, but something went wrong.\nWe've been notified about this issue and we'll take a look at it shortly.\n\nPlease check that any update you tried has not been successful before trying it again."
        end
      }
    end
  end

  def rescue_action_locally(exception)
    respond_to do |want|
      want.html {
        super(exception)
      }
      want.js {
        render :update do |page|
          page.alert "Oops! I made a mistake\n#{exception.class}: #{exception.message}\nCheck the logs for more detail."
        end
      }
    end
  end
end

config_files_check.rb

# used in deploy.rb too
REQUIRED_CONFIG_FILES = ['config/database.yml']

root_path = defined?(Rails) ? Rails.root : "#{File.dirname(__FILE__)}/../.."
REQUIRED_CONFIG_FILES.each do |f|
  raise Exception, "config file #{f} missed" unless File.exist? File.join(root_path, f)
end

noisy_protected_attribute_removal.rb

if Rails.env.development?
  ActiveRecord::Base.class_eval do
    def log_protected_attribute_removal(*attributes)
      raise "Can't mass-assign these protected attributes: #{attributes.join(', ')}"
    end
  end
end