stack.rb in hanami-2.0.0.beta2

- old
+ new

@@ -1,22 +1,37 @@
 # frozen_string_literal: true
 
-require "rack/builder"
-
 module Hanami
   class Slice
     module Routing
-      # Hanami::Applicatione::Router middleware stack
-      #
       # @since 2.0.0
       # @api private
       module Middleware
-        # Middleware stack
+        # Wraps a rack app with a middleware stack
         #
+        # We use this class to add middlewares to the rack application generated
+        # from {Hanami::Slice::Router}.
+        #
+        # ```
+        # stack = Hanami::Slice::Routing::Middleware::Stack.new
+        # stack.use(Rack::ContentType, "text/html")
+        # stack.to_rack_app(a_rack_app)
+        # ```
+        #
+        # Middlewares can be mounted on specific paths:
+        #
+        # ```
+        # stack.with("/api") do
+        #   stack.use(Rack::ContentType, "application/json")
+        # end
+        # ```
+        #
         # @since 2.0.0
         # @api private
         class Stack
+          include Enumerable
+
           # @since 2.0.0
           # @api private
           ROOT_PREFIX = "/"
           private_constant :ROOT_PREFIX
 
@@ -75,9 +90,15 @@
           end
 
           # @since 2.0.0
           # @api private
           def to_rack_app(app)
+            unless Hanami.bundled?("rack")
+              raise "Add \"rack\" to your `Gemfile` to run Hanami as a rack app"
+            end
+
+            require "rack/builder"
+
             s = self
 
             Rack::Builder.new do
               s.each do |prefix, stack|
                 s.mapped(self, prefix) do