Implement ArraySerializer and move old serialization API to a new nam…

…espace.

The following constants were renamed:

  ActiveModel::Serialization     => ActiveModel::Serializable
  ActiveModel::Serializers::JSON => ActiveModel::Serializable::JSON
  ActiveModel::Serializers::Xml  => ActiveModel::Serializable::XML

The main motivation for such a change is that `ActiveModel::Serializers::JSON`
was not actually a serializer, but a module that when included allows the target to be serializable to JSON.

With such changes, we were able to clean up the namespace to add true serializers as the ArraySerializer.

activemodel/lib/active_model.rb

@@ -29,6 +29,7 @@
 module ActiveModel
   extend ActiveSupport::Autoload
 
+  autoload :ArraySerializer, 'active_model/serializer'
   autoload :AttributeMethods
   autoload :BlockValidator, 'active_model/validator'
   autoload :Callbacks
@@ -43,8 +44,9 @@ module ActiveModel
   autoload :Observer, 'active_model/observing'
   autoload :Observing
   autoload :SecurePassword
-  autoload :Serializer
+  autoload :Serializable
   autoload :Serialization
+  autoload :Serializer
   autoload :TestCase
   autoload :Translation
   autoload :Validations

activemodel/lib/active_model/serializable.rb

@@ -0,0 +1,156 @@
+require 'active_support/core_ext/hash/except'
+require 'active_support/core_ext/hash/slice'
+require 'active_support/core_ext/array/wrap'
+
+module ActiveModel
+  # == Active Model Serializable
+  #
+  # Provides a basic serialization to a serializable_hash for your object.
+  #
+  # A minimal implementation could be:
+  #
+  #   class Person
+  #
+  #     include ActiveModel::Serializable
+  #
+  #     attr_accessor :name
+  #
+  #     def attributes
+  #       {'name' => name}
+  #     end
+  #
+  #   end
+  #
+  # Which would provide you with:
+  #
+  #   person = Person.new
+  #   person.serializable_hash   # => {"name"=>nil}
+  #   person.name = "Bob"
+  #   person.serializable_hash   # => {"name"=>"Bob"}
+  #
+  # You need to declare some sort of attributes hash which contains the attributes
+  # you want to serialize and their current value.
+  #
+  # Most of the time though, you will want to include the JSON or XML
+  # serializations. Both of these modules automatically include the
+  # ActiveModel::Serialization module, so there is no need to explicitly
+  # include it.
+  #
+  # So a minimal implementation including XML and JSON would be:
+  #
+  #   class Person
+  #
+  #     include ActiveModel::Serializable::JSON
+  #     include ActiveModel::Serializable::XML
+  #
+  #     attr_accessor :name
+  #
+  #     def attributes
+  #       {'name' => name}
+  #     end
+  #
+  #   end
+  #
+  # Which would provide you with:
+  #
+  #   person = Person.new
+  #   person.serializable_hash   # => {"name"=>nil}
+  #   person.as_json             # => {"name"=>nil}
+  #   person.to_json             # => "{\"name\":null}"
+  #   person.to_xml              # => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<serial-person...
+  #
+  #   person.name = "Bob"
+  #   person.serializable_hash   # => {"name"=>"Bob"}
+  #   person.as_json             # => {"name"=>"Bob"}
+  #   person.to_json             # => "{\"name\":\"Bob\"}"
+  #   person.to_xml              # => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<serial-person...
+  #
+  # Valid options are <tt>:only</tt>, <tt>:except</tt> and <tt>:methods</tt> .
+  module Serializable
+    extend ActiveSupport::Concern
+
+    autoload :JSON, "active_model/serializable/json"
+    autoload :XML,  "active_model/serializable/xml"
+
+    include ActiveModel::Serializer::Scope
+
+    module ClassMethods #:nodoc:
+      def _model_serializer
+        @_model_serializer ||= ActiveModel::Serializer::Finder.find(self, self)
+      end
+    end
+
+    def serializable_hash(options = nil)
+      options ||= {}
+
+      attribute_names = attributes.keys.sort
+      if only = options[:only]
+        attribute_names &= Array.wrap(only).map(&:to_s)
+      elsif except = options[:except]
+        attribute_names -= Array.wrap(except).map(&:to_s)
+      end
+
+      hash = {}
+      attribute_names.each { |n| hash[n] = read_attribute_for_serialization(n) }
+
+      method_names = Array.wrap(options[:methods]).select { |n| respond_to?(n) }
+      method_names.each { |n| hash[n] = send(n) }
+
+      serializable_add_includes(options) do |association, records, opts|
+        hash[association] = if records.is_a?(Enumerable)
+          records.map { |a| a.serializable_hash(opts) }
+        else
+          records.serializable_hash(opts)
+        end
+      end
+
+      hash
+    end
+
+    # Returns a model serializer for this object considering its namespace.
+    def model_serializer
+      self.class._model_serializer
+    end
+
+  private
+
+    # Hook method defining how an attribute value should be retrieved for
+    # serialization. By default this is assumed to be an instance named after
+    # the attribute. Override this method in subclasses should you need to
+    # retrieve the value for a given attribute differently:
+    #
+    #   class MyClass
+    #     include ActiveModel::Validations
+    #
+    #     def initialize(data = {})
+    #       @data = data
+    #     end
+    #
+    #     def read_attribute_for_serialization(key)
+    #       @data[key]
+    #     end
+    #   end
+    #
+    alias :read_attribute_for_serialization :send
+
+    # Add associations specified via the <tt>:include</tt> option.
+    #
+    # Expects a block that takes as arguments:
+    #   +association+ - name of the association
+    #   +records+     - the association record(s) to be serialized
+    #   +opts+        - options for the association records
+    def serializable_add_includes(options = {}) #:nodoc:
+      return unless include = options[:include]
+
+      unless include.is_a?(Hash)
+        include = Hash[Array.wrap(include).map { |n| n.is_a?(Hash) ? n.to_a.first : [n, {}] }]
+      end
+
+      include.each do |association, opts|
+        if records = send(association)
+          yield association, records, opts
+        end
+      end
+    end
+  end
+end

activemodel/lib/active_model/serializable/json.rb

@@ -0,0 +1,108 @@
+require 'active_support/json'
+require 'active_support/core_ext/class/attribute'
+
+module ActiveModel
+  # == Active Model Serializable as JSON
+  module Serializable
+    module JSON
+      extend ActiveSupport::Concern
+      include ActiveModel::Serializable
+
+      included do
+        extend ActiveModel::Naming
+
+        class_attribute :include_root_in_json
+        self.include_root_in_json = true
+      end
+
+      # Returns a hash representing the model. Some configuration can be
+      # passed through +options+.
+      #
+      # The option <tt>include_root_in_json</tt> controls the top-level behavior
+      # of +as_json+. If true (the default) +as_json+ will emit a single root
+      # node named after the object's type. For example:
+      #
+      #   user = User.find(1)
+      #   user.as_json
+      #   # => { "user": {"id": 1, "name": "Konata Izumi", "age": 16,
+      #                   "created_at": "2006/08/01", "awesome": true} }
+      #
+      #   ActiveRecord::Base.include_root_in_json = false
+      #   user.as_json
+      #   # => {"id": 1, "name": "Konata Izumi", "age": 16,
+      #         "created_at": "2006/08/01", "awesome": true}
+      #
+      # This behavior can also be achieved by setting the <tt>:root</tt> option to +false+ as in:
+      #
+      #   user = User.find(1)
+      #   user.as_json(root: false)
+      #   # =>  {"id": 1, "name": "Konata Izumi", "age": 16,
+      #          "created_at": "2006/08/01", "awesome": true}
+      #
+      # The remainder of the examples in this section assume include_root_in_json is set to
+      # <tt>false</tt>.
+      #
+      # Without any +options+, the returned Hash will include all the model's
+      # attributes. For example:
+      #
+      #   user = User.find(1)
+      #   user.as_json
+      #   # => {"id": 1, "name": "Konata Izumi", "age": 16,
+      #         "created_at": "2006/08/01", "awesome": true}
+      #
+      # The <tt>:only</tt> and <tt>:except</tt> options can be used to limit the attributes
+      # included, and work similar to the +attributes+ method. For example:
+      #
+      #   user.as_json(:only => [ :id, :name ])
+      #   # => {"id": 1, "name": "Konata Izumi"}
+      #
+      #   user.as_json(:except => [ :id, :created_at, :age ])
+      #   # => {"name": "Konata Izumi", "awesome": true}
+      #
+      # To include the result of some method calls on the model use <tt>:methods</tt>:
+      #
+      #   user.as_json(:methods => :permalink)
+      #   # => {"id": 1, "name": "Konata Izumi", "age": 16,
+      #         "created_at": "2006/08/01", "awesome": true,
+      #         "permalink": "1-konata-izumi"}
+      #
+      # To include associations use <tt>:include</tt>:
+      #
+      #   user.as_json(:include => :posts)
+      #   # => {"id": 1, "name": "Konata Izumi", "age": 16,
+      #         "created_at": "2006/08/01", "awesome": true,
+      #         "posts": [{"id": 1, "author_id": 1, "title": "Welcome to the weblog"},
+      #                   {"id": 2, author_id: 1, "title": "So I was thinking"}]}
+      #
+      # Second level and higher order associations work as well:
+      #
+      #   user.as_json(:include => { :posts => {
+      #                                  :include => { :comments => {
+      #                                                :only => :body } },
+      #                                  :only => :title } })
+      #   # => {"id": 1, "name": "Konata Izumi", "age": 16,
+      #         "created_at": "2006/08/01", "awesome": true,
+      #         "posts": [{"comments": [{"body": "1st post!"}, {"body": "Second!"}],
+      #                    "title": "Welcome to the weblog"},
+      #                   {"comments": [{"body": "Don't think too hard"}],
+      #                    "title": "So I was thinking"}]}
+      def as_json(options = nil)
+        root = include_root_in_json
+        root = options[:root] if options.try(:key?, :root)
+        if root
+          root = self.class.model_name.element if root == true
+          { root => serializable_hash(options) }
+        else
+          serializable_hash(options)
+        end
+      end
+
+      def from_json(json, include_root=include_root_in_json)
+        hash = ActiveSupport::JSON.decode(json)
+        hash = hash.values.first if include_root
+        self.attributes = hash
+        self
+      end
+    end
+  end
+end