Drop MultiJson in favor of stdlib JSON

Closes rails#409, rails#419.

Author: georgeclaghorn

README.md

@@ -183,7 +183,7 @@ json.partial! partial: 'posts/post', collection: @posts, as: :post
 json.comments @post.comments, partial: 'comments/comment', as: :comment
 ```
 
-The `as: :some_symbol` is used with partials. It will take care of mapping the passed in object to a variable for the partial. If the value is a collection (either implicitly or explicitly by using the `collection:` option, then each value of the collection is passed to the partial as the variable `some_symbol`. If the value is a singular object, then the object is passed to the partial as the variable `some_symbol`. 
+The `as: :some_symbol` is used with partials. It will take care of mapping the passed in object to a variable for the partial. If the value is a collection (either implicitly or explicitly by using the `collection:` option, then each value of the collection is passed to the partial as the variable `some_symbol`. If the value is a singular object, then the object is passed to the partial as the variable `some_symbol`.
 
 Be sure not to confuse the `as:` option to mean nesting of the partial. For example:
 
@@ -274,21 +274,6 @@ environment.rb for example):
 Jbuilder.key_format camelize: :lower
 ```
 
-Faster JSON backends
---------------------
-
-Jbuilder uses MultiJson, which by default will use the JSON gem. That gem is
-currently tangled with ActiveSupport's all-Ruby `#to_json` implementation,
-which is slow (fixed in Rails >= 4.1). For faster Jbuilder rendering, you can
-specify something like the Yajl JSON generator instead. You'll need to include
-the `yajl-ruby` gem in your Gemfile and then set the following configuration
-for MultiJson:
-
-``` ruby
-require 'multi_json'
-MultiJson.use :yajl
- ```
-
 ## Contributing to Jbuilder
 
 Jbuilder is the work of many contributors. You're encouraged to submit pull requests, propose

jbuilder.gemspec

@@ -10,7 +10,6 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 1.9.3'
 
   s.add_dependency 'activesupport', '>= 4.2.0'
-  s.add_dependency 'multi_json',    '>= 1.2'
 
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- test/*`.split("\n")

lib/jbuilder.rb

@@ -2,7 +2,7 @@
 require 'jbuilder/blank'
 require 'jbuilder/key_formatter'
 require 'jbuilder/errors'
-require 'multi_json'
+require 'json'
 require 'ostruct'
 
 class Jbuilder
@@ -247,7 +247,7 @@ def merge!(hash_or_array)
 
   # Encodes the current builder as JSON.
   def target!
-    ::MultiJson.dump(@attributes)
+    ::JSON.dump(@attributes)
   end
 
   private

test/jbuilder_template_test.rb

@@ -195,7 +195,7 @@ class JbuilderTemplateTest < ActiveSupport::TestCase
       end
     JBUILDER
 
-    assert_equal MultiJson.dump(name: "Hit"), Rails.cache.read("jbuilder/root/cache-key")
+    assert_equal JSON.dump(name: "Hit"), Rails.cache.read("jbuilder/root/cache-key")
 
     result = render(<<-JBUILDER)
       json.cache_root! "cache-key" do
@@ -223,7 +223,7 @@ class JbuilderTemplateTest < ActiveSupport::TestCase
       end
     JBUILDER
 
-    assert_equal MultiJson.dump(%w[ a b c ]), Rails.cache.read("jbuilder/root/cache-key")
+    assert_equal JSON.dump(%w[ a b c ]), Rails.cache.read("jbuilder/root/cache-key")
 
     assert_equal %w[ a b c ], render(<<-JBUILDER)
       json.cache_root! "cache-key" do
@@ -285,7 +285,7 @@ class JbuilderTemplateTest < ActiveSupport::TestCase
 
   private
     def render(*args)
-      MultiJson.load render_without_parsing(*args)
+      JSON.load render_without_parsing(*args)
     end
 
     def render_without_parsing(source, assigns = {})