Second attempt.

app/helpers/woo/render_helper.rb

@@ -0,0 +1,53 @@
+module Woo
+  module RenderHelper
+    DEFAULT_VIEW_CONTEXTS = [
+      Haml::Helpers,
+      StyleguideHelper
+    ]
+
+    module FallbackDelegationHelper
+      def method_missing(name, *args, &block)
+        if respond_to?(name, true)
+          send(name, *args, &block)
+        elsif controller.respond_to?(name, true)
+          controller.send(name, *args, &block)
+        else
+          super(name, *args, &block)
+        end
+      end
+    end
+
+    def application_view_context
+      view_paths = Rails.application.config.paths['app/views']
+
+      @app_view_context ||= ActionView::Base.new(view_paths, {}, controller).tap do |context|
+        view_contexts.each { |mod| context.extend(mod) }
+        context.define_singleton_method(:protect_against_forgery?) { nil }
+      end
+    end
+
+    def application_view_paths
+      @app_view_paths ||= Rails.application.config.paths['app/views']
+    end
+
+    def engine_view_context
+      @engine_view_context ||= controller.view_context.tap do |context|
+        context.extend(FallbackDelegationHelper)
+      end
+    end
+
+    def haml_buffer
+      @haml_buffer ||= Haml::Buffer.new(nil, Haml::Options.new.for_buffer)
+    end
+
+    def render_haml_string(contents)
+      Haml::Engine.new(contents).render(engine_view_context)
+    rescue ActionView::MissingTemplate, NoMethodError, NameError
+      Haml::Engine.new(contents).render(application_view_context)
+    end
+
+    def view_contexts
+      @view_contexts ||= DEFAULT_VIEW_CONTEXTS + Rails.application.config.woo.view_contexts
+    end
+  end
+end

app/helpers/woo/styleguide_helper.rb

@@ -1,5 +1,6 @@
 module Woo
   module StyleguideHelper
+    include RenderHelper
 
     BASE_PATH = "app/views/styleguide"
 
@@ -15,23 +16,6 @@ def current_page(folder, page)
       page_hash(filepath)
     end
 
-    def render_haml_string(contents)
-      context = ActionView::Base.new(controller.view_context, {}, controller)
-      context.singleton_class.send(:include, Rails.application.routes.url_helpers)
-
-      context.define_singleton_method(:method_missing) do |name, *args, &block|
-        if respond_to?(name, true)
-          send(name, *args, &block)
-        elsif controller.respond_to?(name, true)
-          controller.send(name, *args, &block)
-        else
-          super(name, *args, &block)
-        end
-      end
-
-      Haml::Engine.new(contents).render(context)
-    end
-
     def load_notes(filepath)
       haml_frontmatter = /^-{1,3}$\n(?<notes_contents>.*)^-{1,3}$\n/m
       match = haml_frontmatter.match(File.read(filepath))

lib/woo/engine.rb

@@ -12,6 +12,7 @@ class Engine < ::Rails::Engine
     config.woo = ActiveSupport::OrderedOptions.new
     config.woo.stylesheets = %w(woo/application application)
     config.woo.javascripts = %w(woo/application application)
+    config.woo.view_contexts = []
 
     initializer 'precompile custom assets' do |app|
       app.config.assets.precompile += app.config.woo.stylesheets