Rename FlattenJson to Attributes (allow plural adapter names)

lib/active_model/serializer/adapter.rb

@@ -5,11 +5,11 @@ module ActiveModel
       ADAPTER_MAP = {}
       private_constant :ADAPTER_MAP if defined?(private_constant)
       extend ActiveSupport::Autoload
+      autoload :Attributes
+      autoload :Null
       autoload :FragmentCache
       autoload :Json
       autoload :JsonApi
-      autoload :Null
-      autoload :FlattenJson
       autoload :CachedSerializer
 
       def self.create(resource, options = {})
@@ -74,7 +74,8 @@ module ActiveModel
         # @api private
         def find_by_name(adapter_name)
           adapter_name = adapter_name.to_s.classify.tr('API', 'Api')
-          ActiveModel::Serializer::Adapter.const_get(adapter_name.to_sym) or # rubocop:disable Style/AndOr
+          "ActiveModel::Serializer::Adapter::#{adapter_name}".safe_constantize ||
+            "ActiveModel::Serializer::Adapter::#{adapter_name.pluralize}".safe_constantize or # rubocop:disable Style/AndOr
             fail UnknownAdapterError
         end
         private :find_by_name

lib/active_model/serializer/adapter/attributes.rb

@@ -1,8 +1,8 @@
-class ActiveModel::Serializer::Adapter::FlattenJson < ActiveModel::Serializer::Adapter::Json
+class ActiveModel::Serializer::Adapter::Attributes < ActiveModel::Serializer::Adapter
         def serializable_hash(options = nil)
           options ||= {}
           if serializer.respond_to?(:each)
-            result = serializer.map { |s| FlattenJson.new(s).serializable_hash(options) }
+            result = serializer.map { |s| Attributes.new(s).serializable_hash(options) }
           else
             hash = {}
 
@@ -43,7 +43,7 @@ class ActiveModel::Serializer::Adapter::FlattenJson < ActiveModel::Serializer::A
 
         private
 
-        # no-op: FlattenJson adapter does not include meta data, because it does not support root.
+        # no-op: Attributes adapter does not include meta data, because it does not support root.
         def include_meta(json)
           json
         end

lib/active_model/serializer/adapter/json.rb

@@ -4,7 +4,7 @@ class ActiveModel::Serializer::Adapter::Json < ActiveModel::Serializer::Adapter
 
         def serializable_hash(options = nil)
           options ||= {}
-          { root => FlattenJson.new(serializer).serializable_hash(options) }
+          { root => Attributes.new(serializer).serializable_hash(options) }
         end
 
         private

lib/active_model/serializer/configuration.rb

@@ -6,7 +6,7 @@ module ActiveModel
 
       included do |base|
         base.config.array_serializer = ActiveModel::Serializer::ArraySerializer
-        base.config.adapter = :flatten_json
+        base.config.adapter = :attributes
         base.config.jsonapi_resource_type = :plural
       end
     end