The new way of showing/rendering all exceptions in Rails 3.2+

rails-3.2-show-exceptions

# put this in an initializer

# a Rails 3.2 addendum for: http://accuser.cc/posts/1-rails-3-0-exception-handling
class MyShowExceptions
    def initialize()
      @@rescue_responses = Hash.new(:internal_server_error)
      @@rescue_responses.update({
                                    'ActionController::RoutingError' => :not_found,
                                    'AbstractController::ActionNotFound' => :not_found,
                                    'ActiveRecord::RecordNotFound' => :not_found,
                                    'ActiveRecord::StaleObjectError' => :conflict,
                                    'ActiveRecord::RecordInvalid' => :unprocessable_entity,
                                    'ActiveRecord::RecordNotSaved' => :unprocessable_entity,
                                    'ActionController::MethodNotAllowed' => :method_not_allowed,
                                    'ActionController::NotImplemented' => :not_implemented,
                                    'ActionController::InvalidAuthenticityToken' => :unprocessable_entity,
                                    'ArgumentError' => :unprocessable_entity
                                })
    end

    def call(env)
      exception = env["action_dispatch.exception"] || Exception.new
      body = ErrorsController.action(@@rescue_responses[exception.class.name]).call(env)
    end
end
# Configure ShowExceptions and pass the only instance of above class to it
Rails.configuration.middleware.use "ActionDispatch::ShowExceptions", MyShowExceptions.new