Change order of Rack middleware execution. Fixes issues experienced with JSONP and Grape Entities

CHANGELOG.md

@@ -1,7 +1,7 @@
 Next Release
 ============
 
-* Your contribution here.
+* [#352](https://github.com/intridea/grape/pull/352): Modified registration/execution order of Rack Middleware. This fixes issues with Rack::JSONP responses that contain a `Grape::Entity` - [@deckchair](https://github.com/deckchair).
 
 0.3.2 (2/28/2013)
 =================

Gemfile

@@ -14,4 +14,5 @@ group :development, :test do
   gem 'rack-test', "~> 0.6.2", :require => "rack/test"
   gem 'github-markup'
   gem 'cookiejar'
+  gem 'rack-contrib'
 end

README.md

@@ -796,6 +796,43 @@ The order for choosing the format is the following.
 * Use the default format, if specified by the `default_format` option.
 * Default to `:txt`.
 
+### JSONP & CORS
+
+Grape does not directly support JSONP or CORS so support is enabled through the use of available Rack middleware
+libraries.
+
+Add the relevant libraries to your Gemfile e.g.
+
+* [JSONP (as part of rack-contrib)](https://github.com/rack/rack-contrib)
+* [CORS](https://github.com/cyu/rack-cors)
+
+```ruby
+require 'rack/contrib'
+require 'rack/cors'
+
+class API < Grape::API
+
+  # Enable JSONP
+  # https://github.com/rack/rack-contrib
+  use Rack::JSONP
+
+  # Enable CORS
+  # https://github.com/cyu/rack-cors
+  use Rack::Cors do
+    allow do
+      origins '*'
+      resource '*', :headers => :any, :methods => :get
+    end
+  end
+
+  format :json
+
+  get '/' do
+    'Hello World'
+  end
+end
+```
+
 ## Content-type
 
 Content-type is set by the formatter. You can override the content-type of the response at runtime

lib/grape/endpoint.rb

@@ -389,6 +389,16 @@ def run(env)
     def build_middleware
       b = Rack::Builder.new
 
+      aggregate_setting(:middleware).each do |m|
+        m = m.dup
+        block = m.pop if m.last.is_a?(Proc)
+        if block
+          b.use *m, &block
+        else
+          b.use *m
+        end
+      end
+
       b.use Rack::Head
       b.use Grape::Middleware::Error,
         :default_status => settings[:default_error_status] || 403,
@@ -417,16 +427,6 @@ def build_middleware
         :formatters => settings[:formatters],
         :parsers => settings[:parsers]
 
-      aggregate_setting(:middleware).each do |m|
-        m = m.dup
-        block = m.pop if m.last.is_a?(Proc)
-        if block
-          b.use *m, &block
-        else
-          b.use *m
-        end
-      end
-
       b
     end
 

spec/grape/entity_spec.rb

@@ -197,14 +197,18 @@ def initialize(args)
       last_response.body.should == '{"example":{"name":"johnnyiller"}}'
     end
 
-    it 'presents with jsonp and a custom formatter' do
+    it 'presents with jsonp utilising Rack::JSONP' do
+      require 'rack/contrib'
+
+      # Include JSONP middleware
+      subject.use Rack::JSONP
+
       entity = Class.new(Grape::Entity)
       entity.root "examples", "example"
       entity.expose :name
 
-      subject.content_type :jsonp, 'application/javascript'
-      subject.formatter :jsonp, lambda { |object, env| object.to_json }
-      subject.format :jsonp
+      # Rack::JSONP expects a standard JSON response
+      subject.format :json
 
       subject.get '/example' do
         c = Class.new do
@@ -216,10 +220,11 @@ def initialize(args)
 
         present c.new({:name => "johnnyiller"}), :with => entity
       end
-      get '/example'
+
+      get '/example?callback=abcDef'
       last_response.status.should == 200
       last_response.headers['Content-type'].should == "application/javascript"
-      last_response.body.should == '{"example":{"name":"johnnyiller"}}'
+      last_response.body.should == 'abcDef({"example":{"name":"johnnyiller"}})'
     end
 
   end