rails/actionpack/lib/abstract_controller/rendering.rb

require "abstract_controller/base"

module AbstractController
  class DoubleRenderError < Error
    DEFAULT_MESSAGE = "Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and at most once per action. Also note that neither redirect nor render terminate execution of the action, so if you want to exit an action after redirecting, you need to do something like \"redirect_to(...) and return\"."

    def initialize(message = nil)
      super(message || DEFAULT_MESSAGE)
    end
  end

  # This is a class to fix I18n global state. Whenever you provide I18n.locale during a request,
  # it will trigger the lookup_context and consequently expire the cache.
  # TODO Add some deprecation warnings to remove I18n.locale from controllers
  class I18nProxy < ::I18n::Config #:nodoc:
    attr_reader :i18n_config, :lookup_context

    def initialize(i18n_config, lookup_context)
      @i18n_config, @lookup_context = i18n_config, lookup_context
    end

    def locale
      @i18n_config.locale
    end

    def locale=(value)
      @i18n_config.locale = value
      @lookup_context.update_details(:locale => @i18n_config.locale)
    end
  end

  module Rendering
    extend ActiveSupport::Concern

    include AbstractController::Assigns
    include AbstractController::ViewPaths

    # Overwrite process to setup I18n proxy.
    def process(*) #:nodoc:
      old_config, I18n.config = I18n.config, I18nProxy.new(I18n.config, lookup_context)
      super
    ensure
      I18n.config = old_config
    end

    # An instance of a view class. The default view class is ActionView::Base
    #
    # The view class must have the following methods:
    # View.for_controller[controller]
    #   Create a new ActionView instance for a controller
    # View#render_template[options]
    #   Returns String with the rendered template
    #
    # Override this method in a module to change the default behavior.
    def view_context
      @_view_context ||= ActionView::Base.for_controller(self)
    end

    # Normalize arguments, options and then delegates render_to_body and
    # sticks the result in self.response_body.
    def render(*args, &block)
      options = _normalize_args(*args, &block)
      _normalize_options(options)
      self.response_body = render_to_body(options)
    end

    # Raw rendering of a template to a Rack-compatible body.
    # :api: plugin
    def render_to_body(options = {})
      _process_options(options)
      _render_template(options)
    end

    # Raw rendering of a template to a string. Just convert the results of
    # render_to_body into a String.
    # :api: plugin
    def render_to_string(options={})
      _normalize_options(options)
      AbstractController::Rendering.body_to_s(render_to_body(options))
    end

    # Find and renders a template based on the options given.
    # :api: private
    def _render_template(options) #:nodoc:
      _evaluate_assigns(view_context)
      view_context.render(options)
    end

    # The prefix used in render "foo" shortcuts.
    def _prefix
      controller_path
    end

    # Return a string representation of a Rack-compatible response body.
    def self.body_to_s(body)
      if body.respond_to?(:to_str)
        body
      else
        strings = []
        body.each { |part| strings << part.to_s }
        body.close if body.respond_to?(:close)
        strings.join
      end
    end

  private

    # Normalize options by converting render "foo" to render :action => "foo" and
    # render "foo/bar" to render :file => "foo/bar".
    def _normalize_args(action=nil, options={})
      case action
      when NilClass
      when Hash
        options, action = action, nil
      when String, Symbol
        action = action.to_s
        key = action.include?(?/) ? :file : :action
        options[key] = action
      else
        options.merge!(:partial => action)
      end

      options
    end

    def _normalize_options(options)
      if options[:partial] == true
        options[:partial] = action_name
      end

      if (options.keys & [:partial, :file, :template]).empty?
        options[:prefix] ||= _prefix
      end

      options[:template] ||= (options[:action] || action_name).to_s
      options
    end

    def _process_options(options)
    end
  end
end