Make serializers serializable, step 1.

lib/active_model/serializer.rb

@@ -113,6 +113,31 @@ def initialize(object, options = {})
       end
     end
 
+    # @return [Hash] containing the attributes and first level
+    # associations, similar to how ActiveModel::Serializers::JSON is used
+    # in ActiveRecord::Base.
+    #
+    # @param options [nil, Hash] The standard options passed to `as_json`.
+    #   See
+    #   https://github.com/rails/rails/blob/v5.0.0.beta2/activemodel/lib/active_model/serializers/json.rb#L17-L101
+    #   https://github.com/rails/rails/blob/v5.0.0.beta2/activemodel/lib/active_model/serialization.rb#L85-L123
+    #   https://github.com/rails/rails/blob/v5.0.0.beta2/activesupport/lib/active_support/core_ext/object/json.rb#L147-L162
+    #
+    # TODO: Move to here the Attributes adapter logic for
+    # +serializable_hash_for_single_resource(options)+
+    def serializable_hash(options = nil)
+      options ||= {}
+      serializable = ActiveModel::SerializableResource.new(object, serializer: self, adapter: :attributes, include: '*')
+      serializable.serializable_hash(options)
+    end
+    alias to_hash serializable_hash
+    alias to_h    serializable_hash
+
+    # @see #serializable_hash
+    def as_json(options = nil)
+      serializable_hash(options)
+    end
+
     # Used by adapter as resource root.
     def json_key
       root || object.class.model_name.to_s.underscore