Add ActiveSupport::JSON and Object#to_json for converting Ruby objects to JSON strings

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3356 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/CHANGELOG

 *SVN*
 
+* Add ActiveSupport::JSON and Object#to_json for converting Ruby objects to JSON strings. [Sam Stephenson]
+
 * Add Object#with_options for DRYing up multiple calls to methods having shared options. [Sam Stephenson]  Example:
 
   ActionController::Routing::Routes.draw do |map|

activesupport/lib/active_support.rb

@@ -34,4 +34,6 @@
 require 'active_support/ordered_options'
 require 'active_support/option_merger'
 
-require 'active_support/values/time_zone'
\ No newline at end of file
+require 'active_support/values/time_zone'
+
+require 'active_support/json'

activesupport/lib/active_support/core_ext/object_and_class.rb

@@ -54,6 +54,17 @@ def suppress(*exception_classes)
   def with_options(options)
     yield ActiveSupport::OptionMerger.new(self, options)
   end
+  
+  def instance_values
+    instance_variables.inject({}) do |values, name|
+      values[name[1..-1]] = instance_variable_get(name)
+      values
+    end
+  end
+  
+  def to_json
+    ActiveSupport::JSON.encode(self)
+  end
 end
 
 class Class #:nodoc:

activesupport/lib/active_support/core_ext/string.rb

@@ -2,10 +2,12 @@
 require File.dirname(__FILE__) + '/string/conversions'
 require File.dirname(__FILE__) + '/string/access'
 require File.dirname(__FILE__) + '/string/starts_ends_with'
+require File.dirname(__FILE__) + '/string/iterators'
 
 class String #:nodoc:
   include ActiveSupport::CoreExtensions::String::Access
   include ActiveSupport::CoreExtensions::String::Conversions
   include ActiveSupport::CoreExtensions::String::Inflections
   include ActiveSupport::CoreExtensions::String::StartsEndsWith
+  include ActiveSupport::CoreExtensions::String::Iterators
 end

activesupport/lib/active_support/core_ext/string/iterators.rb

+require 'strscan'
+
+module ActiveSupport #:nodoc:
+  module CoreExtensions #:nodoc:
+    module String #:nodoc:
+      # Custom string iterators
+      module Iterators
+        # Yields a single-character string for each character in the string.
+        # When $KCODE = 'UTF8', multi-byte characters are yielded appropriately.
+        def each_char
+          scanner, char = StringScanner.new(self), /./mu
+          loop { yield(scanner.scan(char) || break) }
+        end
+      end
+    end
+  end
+end

activesupport/lib/active_support/json.rb

+require 'active_support/json/encoders'
+
+module ActiveSupport
+  module JSON #:nodoc:
+    class CircularReferenceError < StandardError; end
+      
+    class << self
+      REFERENCE_STACK_VARIABLE = :json_reference_stack
+      
+      def encode(value)
+        raise_on_circular_reference(value) do
+          Encoders[value.class].call(value)
+        end
+      end
+      
+      protected
+        def raise_on_circular_reference(value)
+          stack = Thread.current[REFERENCE_STACK_VARIABLE] ||= []
+          raise CircularReferenceError, 'object references itself' if
+            stack.include? value
+          stack << value
+          yield
+        ensure
+          stack.pop
+        end
+    end
+  end
+end

activesupport/lib/active_support/json/encoders.rb

+module ActiveSupport
+  module JSON #:nodoc:
+    module Encoders
+      mattr_accessor :encoders
+      @@encoders = {}
+
+      class << self        
+        def define_encoder(klass, &block)
+          encoders[klass] = block
+        end
+        
+        def [](klass)
+          klass.ancestors.each do |k|
+            encoder = encoders[k]
+            return encoder if encoder
+          end
+        end
+      end
+    end
+  end
+end
+
+Dir[File.dirname(__FILE__) + '/encoders/*.rb'].each do |file|
+  require file[0..-4]
+end

activesupport/lib/active_support/json/encoders/core.rb

+module ActiveSupport
+  module JSON #:nodoc:
+    module Encoders
+      define_encoder Object do |object|
+        object.instance_values.to_json
+      end
+      
+      define_encoder TrueClass do
+        'true'
+      end
+      
+      define_encoder FalseClass do
+        'false'
+      end
+      
+      define_encoder NilClass do
+        'null'
+      end
+      
+      define_encoder String do |string|
+        returning value = '"' do
+          string.each_char do |char|
+            value << case
+            when char == "\010":  '\b'
+            when char == "\f":    '\f'
+            when char == "\n":    '\n'
+            when char == "\r":    '\r'
+            when char == "\t":    '\t'
+            when char == '"':     '\"'
+            when char == '\\':    '\\\\'  
+            when char.length > 1: "\\u#{'%04x' % char.unpack('U').first}"
+            else;                 char
+            end
+          end
+          value << '"'
+        end
+      end
+      
+      define_encoder Numeric do |numeric|
+        numeric.to_s
+      end
+      
+      define_encoder Symbol do |symbol|
+        symbol.to_s.to_json
+      end
+
+      define_encoder Enumerable do |enumerable|
+        "[#{enumerable.map { |value| value.to_json } * ', '}]"
+      end
+      
+      define_encoder Hash do |hash|
+        returning result = '{' do
+          result << hash.map do |pair|
+            pair.map { |value| value.to_json } * ': '
+          end * ', '
+          result << '}'
+        end
+      end
+    end
+  end
+end

activesupport/test/core_ext/object_and_class_ext_test.rb

@@ -104,4 +104,11 @@ def protected_instance_variables
     assert !@dest.instance_variables.include?('@quux')
     assert_equal 'baz', @dest.instance_variable_get('@baz')
   end
+  
+  def test_instance_values
+    object = Object.new
+    object.instance_variable_set :@a, 1
+    object.instance_variable_set :@b, 2
+    assert_equal({'a' => 1, 'b' => 2}, object.instance_values)
+  end
 end

activesupport/test/core_ext/string_ext_test.rb

@@ -89,4 +89,14 @@ def test_starts_ends_with
     assert s.ends_with?('lo')    
     assert !s.ends_with?('el')  
   end
+
+  def test_each_char_with_utf8_string_when_kcode_is_utf8
+    old_kcode, $KCODE = $KCODE, 'UTF8'
+    '€2.99'.each_char do |char|
+      assert_not_equal 1, char.length
+      break
+    end
+  ensure
+    $KCODE = old_kcode
+  end
 end

activesupport/test/json.rb

+$:.unshift File.dirname(__FILE__) + '/../lib'
+require 'active_support'
+require 'test/unit'
+
+class Foo
+  def initialize(a, b)
+    @a, @b = a, b
+  end
+end
+
+class TestJSONEmitters < Test::Unit::TestCase
+  TrueTests    = [[ true,  %(true)  ]]
+  FalseTests   = [[ false, %(false) ]]
+  NilTests     = [[ nil,   %(null)  ]]
+  NumericTests = [[ 1,     %(1)     ],
+                  [ 2.5,   %(2.5)   ]]
+                    
+  StringTests  = [[ 'this is the string',     %("this is the string")         ],
+                  [ 'a "string" with quotes', %("a \\"string\\" with quotes") ]]
+                 
+  ArrayTests   = [[ ['a', 'b', 'c'],          %([\"a\", \"b\", \"c\"])          ],
+                  [ [1, 'a', :b, nil, false], %([1, \"a\", \"b\", null, false]) ]]
+  
+  HashTests    = [[ {:a => :b, :c => :d}, %({\"c\": \"d\", \"a\": \"b\"}) ]]
+                  
+  SymbolTests  = [[ :a,     %("a")    ],
+                  [ :this,  %("this") ],
+                  [ :"a b", %("a b")  ]]
+
+  ObjectTests  = [[ Foo.new(1, 2), %({\"a\": 1, \"b\": 2}) ]]
+  
+  constants.grep(/Tests$/).each do |class_tests|
+    define_method("test_#{class_tests[0..-6].downcase}") do
+      self.class.const_get(class_tests).each do |pair|
+        assert_equal pair.last, pair.first.to_json
+      end
+    end
+  end
+  
+  def test_utf8_string_encoded_properly_when_kcode_is_utf8
+    old_kcode, $KCODE = $KCODE, 'UTF8'
+    assert_equal '"\\u20ac2.99"', '€2.99'.to_json
+    assert_equal '"\\u270e\\u263a"', '✎☺'.to_json
+  ensure
+    $KCODE = old_kcode
+  end
+  
+  def test_exception_raised_when_encoding_circular_reference
+    a = [1]
+    a << a
+    assert_raises(ActiveSupport::JSON::CircularReferenceError) { a.to_json }
+  end
+end