[Perf] Simplify serialization for better performance

BREAKING CHANGE!
This commit introduces one backward incompatibility where redefining
`converter` and `collection_converter` is now no-op.

Author: okuramasafumi

lib/alba/resource.rb

@@ -128,10 +128,6 @@ def hash_from_traits(obj)
         end
       end
 
-      def deprecated_serializable_hash
-        Alba.collection?(@object) ? serializable_hash_for_collection : converter.call(@object)
-      end
-
       def serialize_with(hash)
         serialized_json = encode(hash)
         return serialized_json unless @_layout
@@ -168,18 +164,6 @@ def serializable_hash_for_collection
         end
       end
 
-      def deprecated_serializable_hash_for_collection
-        if @_collection_key
-          @object.to_h do |item|
-            k = item.public_send(@_collection_key)
-            key = Alba.regularize_key(k)
-            [key, converter.call(item)]
-          end
-        else
-          @object.each_with_object([], &collection_converter)
-        end
-      end
-
       # @return [String]
       def fetch_key
         k = Alba.collection?(@object) ? _key_for_collection : _key
@@ -211,21 +195,6 @@ def transforming_root_key?
         @_transforming_root_key
       end
 
-      def converter
-        lambda do |obj|
-          attributes_to_hash(obj, {})
-        end
-      end
-
-      def collection_converter
-        lambda do |obj, a|
-          a << {}
-          h = a.last
-          attributes_to_hash(obj, h)
-          a
-        end
-      end
-
       def attributes_to_hash(obj, hash)
         @_attributes.each do |key, attribute|
           set_key_and_attribute_body_from(obj, key, attribute, hash)
@@ -346,16 +315,8 @@ module ClassMethods
       attr_reader(*INTERNAL_VARIABLES.keys)
 
       # This `method_added` is used for defining "resource methods"
-      def method_added(method_name) # rubocop:disable Metrics/MethodLength
+      def method_added(method_name)
         case method_name
-        when :collection_converter, :converter
-          warn "Defining ##{method_name} methods is deprecated", category: :deprecated, uplevel: 1
-          alias_method :serializable_hash_for_collection, :deprecated_serializable_hash_for_collection
-          private(:serializable_hash_for_collection)
-          alias_method :serializable_hash, :deprecated_serializable_hash
-          alias_method :to_h, :deprecated_serializable_hash
-        when :attributes
-          warn 'Overriding `attributes` is deprecated, use `select` instead.', category: :deprecated, uplevel: 1
         when :select
           @_select_arity = instance_method(:select).arity
         when :_setup # noop

test/resource_test.rb

@@ -128,54 +128,4 @@ def test_include_serializer
       FooSerializer.new(@foo).to_json
     )
   end
-
-  class DeprecatedConverterResource
-    include Alba::Resource
-
-    attributes :id
-
-    private
-
-    def converter
-      ->(o) { o }
-    end
-  end
-
-  def test_deprecated_converter
-    assert_equal @foo, DeprecatedConverterResource.new(@foo).as_json
-  end
-
-  class DeprecatedConverterCollectionResource
-    include Alba::Resource
-
-    attributes :id
-
-    private
-
-    def collection_converter
-      lambda do |obj, a|
-        a << obj
-      end
-    end
-  end
-
-  def test_deprecated_collection_converter
-    assert_equal [@foo], DeprecatedConverterCollectionResource.new([@foo]).as_json
-  end
-
-  def test_deprecated_attributes
-    assert_output('', /Overriding `attributes` is deprecated, use `select` instead./) do
-      Class.new do
-        include Alba::Resource
-
-        attributes :id
-
-        private
-
-        def attributes # rubocop:disable Lint/UselessMethodDefinition
-          super
-        end
-      end
-    end
-  end
 end