Merge pull request #5896 from sferik/revert_5861

Revert #5861. Feature-detect which MultiJson API to use.

activesupport/activesupport.gemspec

@@ -19,5 +19,5 @@ Gem::Specification.new do |s|
   s.rdoc_options.concat ['--encoding',  'UTF-8']
 
   s.add_dependency('i18n',       '~> 0.6')
-  s.add_dependency('multi_json', '>= 1.0', '< 1.3')
+  s.add_dependency('multi_json', '~> 1.0')
 end

activesupport/lib/active_support/json/decoding.rb

@@ -9,7 +9,13 @@ module ActiveSupport
   module JSON
     class << self
       def decode(json, options ={})
-        data = MultiJson.decode(json, options)
+        # Can't reliably detect whether MultiJson responds to load, since it's
+        # a reserved word. Use adapter as a proxy for new features.
+        data = if MultiJson.respond_to?(:adapter)
+          MultiJson.load(json, options)
+        else
+          MultiJson.decode(json, options)
+        end
         if ActiveSupport.parse_json_times
           convert_dates_from(data)
         else
@@ -18,12 +24,20 @@ module ActiveSupport
       end
 
       def engine
-        MultiJson.engine
+        if MultiJson.respond_to?(:adapter)
+          MultiJson.adapter
+        else
+          MultiJson.engine
+        end
       end
       alias :backend :engine
 
       def engine=(name)
-        MultiJson.engine = name
+        if MultiJson.respond_to?(:use)
+          MultiJson.use name
+        else
+          MultiJson.engine = name
+        end
       end
       alias :backend= :engine=