path: root/actionview/lib/action_view/template/handlers.rb

# frozen_string_literal: true

require "active_support/deprecation"

module ActionView #:nodoc:
  # = Action View Template Handlers
  class Template #:nodoc:
    module Handlers #:nodoc:
      autoload :Raw, "action_view/template/handlers/raw"
      autoload :ERB, "action_view/template/handlers/erb"
      autoload :Html, "action_view/template/handlers/html"
      autoload :Builder, "action_view/template/handlers/builder"

      def self.extended(base)
        base.register_default_template_handler :raw, Raw.new
        base.register_template_handler :erb, ERB.new
        base.register_template_handler :html, Html.new
        base.register_template_handler :builder, Builder.new
        base.register_template_handler :ruby, lambda { |_, source| source }
      end

      @@template_handlers = {}
      @@default_template_handlers = nil

      def self.extensions
        @@template_extensions ||= @@template_handlers.keys
      end

      class LegacyHandlerWrapper < SimpleDelegator # :nodoc:
        def call(view, source)
          __getobj__.call(ActionView::Template::LegacyTemplate.new(view, source))
        end
      end

      # Register an object that knows how to handle template files with the given
      # extensions. This can be used to implement new template types.
      # The handler must respond to +:call+, which will be passed the template
      # and should return the rendered template as a String.
      def register_template_handler(*extensions, handler)
        params = if handler.is_a?(Proc)
          handler.parameters
        else
          handler.method(:call).parameters
        end

        unless params.find_all { |type, _| type == :req || type == :opt }.length >= 2
          ActiveSupport::Deprecation.warn <<~eowarn
          Single arity template handlers are deprecated.  Template handlers must
          now accept two parameters, the view object and the source for the view object.
          Change:
            >> #{handler.class}#call(#{params.map(&:last).join(", ")})
          To:
            >> #{handler.class}#call(#{params.map(&:last).join(", ")}, source)
          eowarn
          handler = LegacyHandlerWrapper.new(handler)
        end

        raise(ArgumentError, "Extension is required") if extensions.empty?
        extensions.each do |extension|
          @@template_handlers[extension.to_sym] = handler
        end
        @@template_extensions = nil
      end

      # Opposite to register_template_handler.
      def unregister_template_handler(*extensions)
        extensions.each do |extension|
          handler = @@template_handlers.delete extension.to_sym
          @@default_template_handlers = nil if @@default_template_handlers == handler
        end
        @@template_extensions = nil
      end

      def template_handler_extensions
        @@template_handlers.keys.map(&:to_s).sort
      end

      def registered_template_handler(extension)
        extension && @@template_handlers[extension.to_sym]
      end

      def register_default_template_handler(extension, klass)
        register_template_handler(extension, klass)
        @@default_template_handlers = klass
      end

      def handler_for_extension(extension)
        registered_template_handler(extension) || @@default_template_handlers
      end
    end
  end
end