Apply key transforms to keys referenced in values

CHANGELOG.md

@@ -2,7 +2,11 @@
 
 Breaking changes:
 
+- [#1645](https://github.com/rails-api/active_model_serializers/pull/1645) Changed :dashed key transform to :dash. (@remear)
+- [#1574](https://github.com/rails-api/active_model_serializers/pull/1574) Default key case for the JsonApi adapter changed to dashed. (@remear)
+
 Features:
+- [#1645](https://github.com/rails-api/active_model_serializers/pull/1645) Transform keys referenced in values. (@remear)
 - [#1650](https://github.com/rails-api/active_model_serializers/pull/1650) Fix serialization scope options `scope`, `scope_name`
   take precedence over `serialization_scope` in the controller.
   Fix tests that required tearing down dynamic methods. (@bf4)

active_model_serializers.gemspec

@@ -57,4 +57,10 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'grape', ['>= 0.13', '< 1.0']
   spec.add_development_dependency 'json_schema'
   spec.add_development_dependency 'rake', ['>= 10.0', '< 12.0']
+
+  spec.post_install_message = <<-EOF
+NOTE: The default key case for the JsonApi adapter has changed to dashed.
+See https://github.com/rails-api/active_model_serializers/blob/master/docs/general/key_transform.md
+for more information on configuring this behavior.
+EOF
 end

docs/general/configuration_options.md

@@ -30,20 +30,24 @@ When `false`, serializers must be explicitly specified.
 
 ##### key_transform
 
-The [key transform](key_transform.md) to use.
+The [key transform](key_transforms.md) to use.
 
-Possible values:
 
-- `:camel` - ExampleKey
+| Option | Result |
-- `:camel_lower` - exampleKey
+|----|----|
-- `:dashed` - example-key
+| `:camel` | ExampleKey |
-- `:unaltered` - the original, unaltered key
+| `:camel_lower` | exampleKey |
-- `nil` - use the adapter default
+| `:dash` | example-key |
+| `:unaltered` | the original, unaltered key |
+| `:underscore` | example_key |
+| `nil` | use the adapter default |
 
 Each adapter has a default key transform configured:
 
-- `Json` - `:unaltered`
+| Adapter | Default Key Transform |
-- `JsonApi` - `:dashed`
+|----|----|
+| `Json` | `:unaltered` |
+| `JsonApi` | `:dash` |
 
 `config.key_transform` is a global override of the adapter default. Adapters
 still prefer the render option `:key_transform` over this setting.

docs/general/key_transform.md

@@ -1,34 +0,0 @@
-[Back to Guides](../README.md)
-
-# Key Transforms
-
-Key transforms modify the keys in serialized responses.
-
-Provided key transforms:
-
-- `:camel` - ExampleKey
-- `:camel_lower` - exampleKey
-- `:dashed` - example-key
-- `:unaltered` - the original, unaltered key
-- `nil` - use the adapter default
-
-Key translation precedence is as follows:
-
-##### SerializableResource option
-
-`key_transform` is provided as an option via render.
-
-```render json: posts, each_serializer: PostSerializer, key_transform: :camel_lower```
-
-##### Configuration option
-
-`key_transform` is set in `ActiveModelSerializers.config.key_transform`.
-
-```ActiveModelSerializers.config.key_transform = :camel_lower```
-
-##### Adapter default
-
-Each adapter has a default key transform configured:
-
-- `Json` - `:unaltered`
-- `JsonApi` - `:dashed`

docs/general/key_transforms.md

@@ -0,0 +1,40 @@
+[Back to Guides](../README.md)
+
+# Key Transforms
+
+Key Transforms modify the casing of keys and keys referenced in values in
+serialized responses.
+
+Provided key transforms:
+
+| Option | Result |
+|----|----|
+| `:camel` | ExampleKey |
+| `:camel_lower` | exampleKey |
+| `:dash` | example-key |
+| `:unaltered` | the original, unaltered key |
+| `:underscore` | example_key |
+| `nil` | use the adapter default |
+
+Key translation precedence is as follows:
+
+##### Adapter option
+
+`key_transform` is provided as an option via render.
+
+```render json: posts, each_serializer: PostSerializer, key_transform: :camel_lower```
+
+##### Configuration option
+
+`key_transform` is set in `ActiveModelSerializers.config.key_transform`.
+
+```ActiveModelSerializers.config.key_transform = :camel_lower```
+
+##### Adapter default
+
+Each adapter has a default transform configured:
+
+| Adapter | Default Key Transform |
+|----|----|
+| `Json` | `:unaltered` |
+| `JsonApi` | `:dash` |

lib/active_model_serializers/adapter/base.rb

@@ -58,25 +58,32 @@ module ActiveModelSerializers
         json
       end
 
+      class << self
+        # Sets the default transform for the adapter.
+        #
+        # @return [Symbol] the default transform for the adapter
         def default_key_transform
           :unaltered
         end
 
         # Determines the transform to use in order of precedence:
-      #   serialization context, global config, adapter default.
+        #   adapter option, global config, adapter default.
         #
-      # @param serialization_context [Object] the SerializationContext
+        # @param options [Object]
         # @return [Symbol] the transform to use
-      def key_transform(serialization_context)
+        def transform(options)
-        serialization_context.key_transform ||
+          return options[:key_transform] if options && options[:key_transform]
-        ActiveModelSerializers.config.key_transform ||
+          ActiveModelSerializers.config.key_transform || default_key_transform
-        default_key_transform
         end
 
-      def transform_key_casing!(value, serialization_context)
+        # Transforms the casing of the supplied value.
-        return value unless serialization_context
+        #
-        transform = key_transform(serialization_context)
+        # @param value [Object] the value to be transformed
-        KeyTransform.send(transform, value)
+        # @param options [Object] serializable resource options
+        # @return [Symbol] the default transform for the adapter
+        def transform_key_casing!(value, options)
+          KeyTransform.send(transform(options), value)
+        end
       end
     end
   end

lib/active_model_serializers/adapter/json.rb

@@ -4,7 +4,7 @@ module ActiveModelSerializers
       def serializable_hash(options = nil)
         options ||= {}
         serialized_hash = { root => Attributes.new(serializer, instance_options).serializable_hash(options) }
-        transform_key_casing!(serialized_hash, options[:serialization_context])
+        self.class.transform_key_casing!(serialized_hash, options)
       end
     end
   end

lib/active_model_serializers/adapter/json_api.rb

@@ -37,8 +37,8 @@ module ActiveModelSerializers
         @fieldset = options[:fieldset] || ActiveModel::Serializer::Fieldset.new(options.delete(:fields))
       end
 
-      def default_key_transform
+      def self.default_key_transform
-        :dashed
+        :dash
       end
 
       # {http://jsonapi.org/format/#crud Requests are transactional, i.e. success or failure}
@@ -48,9 +48,9 @@ module ActiveModelSerializers
         document = if serializer.success?
                      success_document(options)
                    else
-                     failure_document
+                     failure_document(options)
                    end
-        transform_key_casing!(document, options[:serialization_context])
+        self.class.transform_key_casing!(document, options)
       end
 
       # {http://jsonapi.org/format/#document-top-level Primary data}
@@ -71,7 +71,7 @@ module ActiveModelSerializers
       def success_document(options)
         is_collection = serializer.respond_to?(:each)
         serializers = is_collection ? serializer : [serializer]
-        primary_data, included = resource_objects_for(serializers)
+        primary_data, included = resource_objects_for(serializers, options)
 
         hash = {}
         # toplevel_data
@@ -148,7 +148,7 @@ module ActiveModelSerializers
       #   }.reject! {|_,v| v.nil? }
       # prs:
       #  https://github.com/rails-api/active_model_serializers/pull/1004
-      def failure_document
+      def failure_document(options)
         hash = {}
         # PR Please :)
         # Jsonapi.add!(hash)
@@ -163,10 +163,10 @@ module ActiveModelSerializers
         #   ]
         if serializer.respond_to?(:each)
           hash[:errors] = serializer.flat_map do |error_serializer|
-            Error.resource_errors(error_serializer)
+            Error.resource_errors(error_serializer, options)
           end
         else
-          hash[:errors] = Error.resource_errors(serializer)
+          hash[:errors] = Error.resource_errors(serializer, options)
         end
         hash
       end
@@ -224,21 +224,21 @@ module ActiveModelSerializers
       #     [x] url helpers https://github.com/rails-api/active_model_serializers/issues/1269
       #   meta
       #     [x] https://github.com/rails-api/active_model_serializers/pull/1340
-      def resource_objects_for(serializers)
+      def resource_objects_for(serializers, options)
         @primary = []
         @included = []
         @resource_identifiers = Set.new
-        serializers.each { |serializer| process_resource(serializer, true) }
+        serializers.each { |serializer| process_resource(serializer, true, options) }
-        serializers.each { |serializer| process_relationships(serializer, @include_tree) }
+        serializers.each { |serializer| process_relationships(serializer, @include_tree, options) }
 
         [@primary, @included]
       end
 
-      def process_resource(serializer, primary)
+      def process_resource(serializer, primary, options)
-        resource_identifier = ResourceIdentifier.new(serializer).as_json
+        resource_identifier = ResourceIdentifier.new(serializer, options).as_json
         return false unless @resource_identifiers.add?(resource_identifier)
 
-        resource_object = resource_object_for(serializer)
+        resource_object = resource_object_for(serializer, options)
         if primary
           @primary << resource_object
         else
@@ -248,21 +248,21 @@ module ActiveModelSerializers
         true
       end
 
-      def process_relationships(serializer, include_tree)
+      def process_relationships(serializer, include_tree, options)
         serializer.associations(include_tree).each do |association|
-          process_relationship(association.serializer, include_tree[association.key])
+          process_relationship(association.serializer, include_tree[association.key], options)
         end
       end
 
-      def process_relationship(serializer, include_tree)
+      def process_relationship(serializer, include_tree, options)
         if serializer.respond_to?(:each)
-          serializer.each { |s| process_relationship(s, include_tree) }
+          serializer.each { |s| process_relationship(s, include_tree, options) }
           return
         end
         return unless serializer && serializer.object
-        return unless process_resource(serializer, false)
+        return unless process_resource(serializer, false, options)
 
-        process_relationships(serializer, include_tree)
+        process_relationships(serializer, include_tree, options)
       end
 
       # {http://jsonapi.org/format/#document-resource-object-attributes Document Resource Object Attributes}
@@ -286,9 +286,9 @@ module ActiveModelSerializers
       end
 
       # {http://jsonapi.org/format/#document-resource-objects Document Resource Objects}
-      def resource_object_for(serializer)
+      def resource_object_for(serializer, options)
         resource_object = cache_check(serializer) do
-          resource_object = ResourceIdentifier.new(serializer).as_json
+          resource_object = ResourceIdentifier.new(serializer, options).as_json
 
           requested_fields = fieldset && fieldset.fields_for(resource_object[:type])
           attributes = attributes_for(serializer, requested_fields)
@@ -297,7 +297,7 @@ module ActiveModelSerializers
         end
 
         requested_associations = fieldset.fields_for(resource_object[:type]) || '*'
-        relationships = relationships_for(serializer, requested_associations)
+        relationships = relationships_for(serializer, requested_associations, options)
         resource_object[:relationships] = relationships if relationships.any?
 
         links = links_for(serializer)
@@ -425,15 +425,16 @@ module ActiveModelSerializers
       #     id: 'required-id',
       #     meta: meta
       #   }.reject! {|_,v| v.nil? }
-      def relationships_for(serializer, requested_associations)
+      def relationships_for(serializer, requested_associations, options)
         include_tree = ActiveModel::Serializer::IncludeTree.from_include_args(requested_associations)
         serializer.associations(include_tree).each_with_object({}) do |association, hash|
           hash[association.key] = Relationship.new(
             serializer,
             association.serializer,
-            association.options,
+            options,
-            association.links,
+            options: association.options,
-            association.meta
+            links: association.links,
+            meta: association.meta
           ).as_json
         end
       end

lib/active_model_serializers/adapter/json_api/deserialization.rb

@@ -182,14 +182,14 @@ module ActiveModelSerializers
           prefix_key = field_key(assoc_name, options).to_s.singularize
           hash =
             if assoc_data.is_a?(Array)
-              { "#{prefix_key}_ids".to_sym => assoc_data.map { |ri| ri[:id] } }
+              { "#{prefix_key}_ids".to_sym => assoc_data.map { |ri| ri['id'] } }
             else
-              { "#{prefix_key}_id".to_sym => assoc_data && assoc_data.is_a?(Hash) ? assoc_data[:id] : nil }
+              { "#{prefix_key}_id".to_sym => assoc_data ? assoc_data['id'] : nil }
             end
 
           polymorphic = (options[:polymorphic] || []).include?(assoc_name.to_sym)
           if polymorphic
-            hash["#{prefix_key}_type".to_sym] = assoc_data.present? ? assoc_data[:type] : nil
+            hash["#{prefix_key}_type".to_sym] = assoc_data.present? ? assoc_data['type'] : nil
           end
 
           hash
@@ -198,7 +198,7 @@ module ActiveModelSerializers
         # @api private
         def parse_relationships(relationships, options)
           transform_keys(relationships, options)
-            .map { |(k, v)| parse_relationship(k, v[:data], options) }
+            .map { |(k, v)| parse_relationship(k, v['data'], options) }
             .reduce({}, :merge)
         end
 

lib/active_model_serializers/adapter/json_api/error.rb

@@ -10,8 +10,10 @@ module ActiveModelSerializers
         #
         # @param [ActiveModel::Serializer::ErrorSerializer] error_serializer
         # @return [Array<Symbol, Array<String>>] i.e. attribute_name, [attribute_errors]
-        def self.resource_errors(error_serializer)
+        def self.resource_errors(error_serializer, options)
           error_serializer.as_json.flat_map do |attribute_name, attribute_errors|
+            attribute_name = JsonApi.send(:transform_key_casing!, attribute_name,
+              options)
             attribute_error_objects(attribute_name, attribute_errors)
           end
         end

lib/active_model_serializers/adapter/json_api/relationship.rb

@@ -6,21 +6,22 @@ module ActiveModelSerializers
         # {http://jsonapi.org/format/#document-links Document Links}
         # {http://jsonapi.org/format/#document-resource-object-linkage Document Resource Relationship Linkage}
         # {http://jsonapi.org/format/#document-meta Docment Meta}
-        def initialize(parent_serializer, serializer, options = {}, links = {}, meta = nil)
+        def initialize(parent_serializer, serializer, serializable_resource_options, args = {})
           @object = parent_serializer.object
           @scope = parent_serializer.scope
-
+          @association_options = args.fetch(:options, {})
-          @options = options
+          @serializable_resource_options = serializable_resource_options
-          @data = data_for(serializer, options)
+          @data = data_for(serializer)
-          @links = links.each_with_object({}) do |(key, value), hash|
+          @links = args.fetch(:links, {}).each_with_object({}) do |(key, value), hash|
             hash[key] = ActiveModelSerializers::Adapter::JsonApi::Link.new(parent_serializer, value).as_json
           end
+          meta = args.fetch(:meta, nil)
           @meta = meta.respond_to?(:call) ? parent_serializer.instance_eval(&meta) : meta
         end
 
         def as_json
           hash = {}
-          hash[:data] = data if options[:include_data]
+          hash[:data] = data if association_options[:include_data]
           links = self.links
           hash[:links] = links if links.any?
           meta = self.meta
@@ -31,17 +32,18 @@ module ActiveModelSerializers
 
         protected
 
-        attr_reader :object, :scope, :data, :options, :links, :meta
+        attr_reader :object, :scope, :data, :serializable_resource_options,
+          :association_options, :links, :meta
 
         private
 
-        def data_for(serializer, options)
+        def data_for(serializer)
           if serializer.respond_to?(:each)
-            serializer.map { |s| ResourceIdentifier.new(s).as_json }
+            serializer.map { |s| ResourceIdentifier.new(s, serializable_resource_options).as_json }
-          elsif options[:virtual_value]
+          elsif association_options[:virtual_value]
-            options[:virtual_value]
+            association_options[:virtual_value]
           elsif serializer && serializer.object
-            ResourceIdentifier.new(serializer).as_json
+            ResourceIdentifier.new(serializer, serializable_resource_options).as_json
           end
         end
       end

lib/active_model_serializers/adapter/json_api/resource_identifier.rb

@@ -3,9 +3,10 @@ module ActiveModelSerializers
     class JsonApi
       class ResourceIdentifier
         # {http://jsonapi.org/format/#document-resource-identifier-objects Resource Identifier Objects}
-        def initialize(serializer)
+        def initialize(serializer, options)
           @id   = id_for(serializer)
-          @type = type_for(serializer)
+          @type = JsonApi.send(:transform_key_casing!, type_for(serializer),
+            options)
         end
 
         def as_json

lib/active_model_serializers/key_transform.rb

@@ -4,47 +4,67 @@ module ActiveModelSerializers
   module KeyTransform
     module_function
 
-    # Transforms keys to UpperCamelCase or PascalCase.
+    # Transforms values to UpperCamelCase or PascalCase.
     #
     # @example:
     #    "some_key" => "SomeKey",
     # @see {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb#L66-L76 ActiveSupport::Inflector.camelize}
-    def camel(hash)
+    def camel(value)
-      hash.deep_transform_keys! { |key| key.to_s.camelize.to_sym }
+      case value
+      when Hash then value.deep_transform_keys! { |key| camel(key) }
+      when Symbol then camel(value.to_s).to_sym
+      when String then value.underscore.camelize
+      else value
+      end
     end
 
-    # Transforms keys to camelCase.
+    # Transforms values to camelCase.
     #
     # @example:
     #    "some_key" => "someKey",
     # @see {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb#L66-L76 ActiveSupport::Inflector.camelize}
-    def camel_lower(hash)
+    def camel_lower(value)
-      hash.deep_transform_keys! { |key| key.to_s.camelize(:lower).to_sym }
+      case value
+      when Hash then value.deep_transform_keys! { |key| camel_lower(key) }
+      when Symbol then camel_lower(value.to_s).to_sym
+      when String then value.underscore.camelize(:lower)
+      else value
+      end
     end
 
-    # Transforms keys to dashed-case.
+    # Transforms values to dashed-case.
     # This is the default case for the JsonApi adapter.
     #
     # @example:
     #    "some_key" => "some-key",
     # @see {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb#L185-L187 ActiveSupport::Inflector.dasherize}
-    def dashed(hash)
+    def dash(value)
-      hash.deep_transform_keys! { |key| key.to_s.dasherize.to_sym }
+      case value
+      when Hash then value.deep_transform_keys! { |key| dash(key) }
+      when Symbol then dash(value.to_s).to_sym
+      when String then value.underscore.dasherize
+      else value
+      end
     end
 
-    # Transforms keys to underscore.
+    # Transforms values to underscore_case.
     # This is the default case for deserialization in the JsonApi adapter.
     #
     # @example:
     #    "some-key" => "some_key",
     # @see {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb#L89-L98 ActiveSupport::Inflector.underscore}
-    def underscore(hash)
+    def underscore(value)
-      hash.deep_transform_keys! { |key| key.to_s.underscore.to_sym }
+      case value
+      when Hash then value.deep_transform_keys! { |key| underscore(key) }
+      when Symbol then underscore(value.to_s).to_sym
+      when String then value.underscore
+      else value
+      end
     end
 
-    # Returns the hash unaltered
+    # Returns the value unaltered
-    def unaltered(hash)
+    def unaltered(value)
-      hash
+      value
     end
   end
 end

lib/active_model_serializers/serialization_context.rb

@@ -27,7 +27,6 @@ module ActiveModelSerializers
       @query_parameters = request.query_parameters
       @url_helpers = options.delete(:url_helpers) || self.class.url_helpers
       @default_url_options = options.delete(:default_url_options) || self.class.default_url_options
-      @key_transform = options.delete(:key_transform)
     end
   end
 end

test/action_controller/json_api/transform_test.rb

@@ -10,7 +10,7 @@ module ActionController
             type 'posts'
             attributes :title, :body, :publish_at
             belongs_to :author
-            has_many :comments
+            has_many :top_comments
 
             link(:post_authors) { 'https://example.com/post_authors' }
 
@@ -28,9 +28,9 @@ module ActionController
             attributes :first_name, :last_name
           end
 
-          Comment = Class.new(::Model)
+          TopComment = Class.new(::Model)
-          class CommentSerializer < ActiveModel::Serializer
+          class TopCommentSerializer < ActiveModel::Serializer
-            type 'comments'
+            type 'top_comments'
             attributes :body
             belongs_to :author
           end
@@ -38,28 +38,28 @@ module ActionController
           def setup_post
             ActionController::Base.cache_store.clear
             @author = Author.new(id: 1, first_name: 'Bob', last_name: 'Jones')
-            @comment1 = Comment.new(id: 7, body: 'cool', author: @author)
+            @comment1 = TopComment.new(id: 7, body: 'cool', author: @author)
-            @comment2 = Comment.new(id: 12, body: 'awesome', author: @author)
+            @comment2 = TopComment.new(id: 12, body: 'awesome', author: @author)
             @post = Post.new(id: 1337, title: 'Title 1', body: 'Body 1',
-                             author: @author, comments: [@comment1, @comment2],
+                             author: @author, top_comments: [@comment1, @comment2],
                              publish_at: '2020-03-16T03:55:25.291Z')
             @comment1.post = @post
             @comment2.post = @post
           end
 
-          def render_resource_with_key_transform
+          def render_resource_with_transform
             setup_post
             render json: @post, serializer: PostSerializer, adapter: :json_api,
                    key_transform: :camel
           end
 
-          def render_resource_with_key_transform_nil
+          def render_resource_with_transform_nil
             setup_post
             render json: @post, serializer: PostSerializer, adapter: :json_api,
                    key_transform: nil
           end
 
-          def render_resource_with_key_transform_with_global_config
+          def render_resource_with_transform_with_global_config
             setup_post
             old_transform = ActiveModelSerializers.config.key_transform
             ActiveModelSerializers.config.key_transform = :camel_lower
@@ -70,13 +70,13 @@ module ActionController
 
         tests KeyTransformTestController
 
-        def test_render_resource_with_key_transform
+        def test_render_resource_with_transform
-          get :render_resource_with_key_transform
+          get :render_resource_with_transform
           response = JSON.parse(@response.body)
           expected = {
             'Data' => {
               'Id' => '1337',
-              'Type' => 'posts',
+              'Type' => 'Posts',
               'Attributes' => {
                 'Title' => 'Title 1',
                 'Body' => 'Body 1',
@@ -86,13 +86,13 @@ module ActionController
                 'Author' => {
                   'Data' => {
                     'Id' => '1',
-                    'Type' => 'authors'
+                    'Type' => 'Authors'
                   }
                 },
-                'Comments' => {
+                'TopComments' => {
                   'Data' => [
-                    { 'Id' => '7', 'Type' => 'comments' },
+                    { 'Id' => '7', 'Type' => 'TopComments' },
-                    { 'Id' => '12', 'Type' => 'comments' }
+                    { 'Id' => '12', 'Type' => 'TopComments' }
                   ]
                 }
               },
@@ -105,8 +105,8 @@ module ActionController
           assert_equal expected, response
         end
 
-        def test_render_resource_with_key_transform_nil
+        def test_render_resource_with_transform_nil
-          get :render_resource_with_key_transform_nil
+          get :render_resource_with_transform_nil
           response = JSON.parse(@response.body)
           expected = {
             'data' => {
@@ -124,10 +124,10 @@ module ActionController
                     'type' => 'authors'
                   }
                 },
-                'comments' => {
+                'top-comments' => {
                   'data' => [
-                    { 'id' => '7', 'type' => 'comments' },
+                    { 'id' => '7', 'type' => 'top-comments' },
-                    { 'id' => '12', 'type' => 'comments' }
+                    { 'id' => '12', 'type' => 'top-comments' }
                   ]
                 }
               },
@@ -140,8 +140,8 @@ module ActionController
           assert_equal expected, response
         end
 
-        def test_render_resource_with_key_transform_with_global_config
+        def test_render_resource_with_transform_with_global_config
-          get :render_resource_with_key_transform_with_global_config
+          get :render_resource_with_transform_with_global_config
           response = JSON.parse(@response.body)
           expected =  {
             'data' => {
@@ -159,10 +159,10 @@ module ActionController
                     'type' => 'authors'
                   }
                 },
-                'comments' => {
+                'topComments' => {
                   'data' => [
-                    { 'id' => '7', 'type' => 'comments' },
+                    { 'id' => '7', 'type' => 'topComments' },
-                    { 'id' => '12', 'type' => 'comments' }
+                    { 'id' => '12', 'type' => 'topComments' }
                   ]
                 }
               },

test/active_model_serializers/key_transform_test.rb

@@ -0,0 +1,263 @@
+require 'test_helper'
+
+class ActiveModelSerializers::KeyTransformTest < ActiveSupport::TestCase
+  def test_camel
+    obj = Object.new
+    scenarios = [
+      {
+        value: { :"some-key" => 'value' },
+        expected: { :SomeKey => 'value' }
+      },
+      {
+        value: { :someKey => 'value' },
+        expected: { :SomeKey => 'value' }
+      },
+      {
+        value: { :some_key => 'value' },
+        expected: { :SomeKey => 'value' }
+      },
+      {
+        value: { 'some-key' => 'value' },
+        expected: { 'SomeKey' => 'value' }
+      },
+      {
+        value: { 'someKey' => 'value' },
+        expected: { 'SomeKey' => 'value' }
+      },
+      {
+        value: { 'some_key' => 'value' },
+        expected: { 'SomeKey' => 'value' }
+      },
+      {
+        value: :"some-value",
+        expected: :SomeValue
+      },
+      {
+        value: :some_value,
+        expected: :SomeValue
+      },
+      {
+        value: :someValue,
+        expected: :SomeValue
+      },
+      {
+        value: 'some-value',
+        expected: 'SomeValue'
+      },
+      {
+        value: 'someValue',
+        expected: 'SomeValue'
+      },
+      {
+        value: 'some_value',
+        expected: 'SomeValue'
+      },
+      {
+        value: obj,
+        expected: obj
+      },
+      {
+        value: nil,
+        expected: nil
+      }
+    ]
+    scenarios.each do |s|
+      result = ActiveModelSerializers::KeyTransform.camel(s[:value])
+      assert_equal s[:expected], result
+    end
+  end
+
+  def test_camel_lower
+    obj = Object.new
+    scenarios = [
+      {
+        value: { :"some-key" => 'value' },
+        expected: { :someKey => 'value' }
+      },
+      {
+        value: { :SomeKey => 'value' },
+        expected: { :someKey => 'value' }
+      },
+      {
+        value: { :some_key => 'value' },
+        expected: { :someKey => 'value' }
+      },
+      {
+        value: { 'some-key' => 'value' },
+        expected: { 'someKey' => 'value' }
+      },
+      {
+        value: { 'SomeKey' => 'value' },
+        expected: { 'someKey' => 'value' }
+      },
+      {
+        value: { 'some_key' => 'value' },
+        expected: { 'someKey' => 'value' }
+      },
+      {
+        value: :"some-value",
+        expected: :someValue
+      },
+      {
+        value: :SomeValue,
+        expected: :someValue
+      },
+      {
+        value: :some_value,
+        expected: :someValue
+      },
+      {
+        value: 'some-value',
+        expected: 'someValue'
+      },
+      {
+        value: 'SomeValue',
+        expected: 'someValue'
+      },
+      {
+        value: 'some_value',
+        expected: 'someValue'
+      },
+      {
+        value: obj,
+        expected: obj
+      },
+      {
+        value: nil,
+        expected: nil
+      }
+    ]
+    scenarios.each do |s|
+      result = ActiveModelSerializers::KeyTransform.camel_lower(s[:value])
+      assert_equal s[:expected], result
+    end
+  end
+
+  def test_dash
+    obj = Object.new
+    scenarios = [
+      {
+        value: { :some_key => 'value' },
+        expected: { :"some-key" => 'value' }
+      },
+      {
+        value: { 'some_key' => 'value' },
+        expected: { 'some-key' => 'value' }
+      },
+      {
+        value: { :SomeKey => 'value' },
+        expected: { :"some-key" => 'value' }
+      },
+      {
+        value: { 'SomeKey' => 'value' },
+        expected: { 'some-key' => 'value' }
+      },
+      {
+        value: { :someKey => 'value' },
+        expected: { :"some-key" => 'value' }
+      },
+      {
+        value: { 'someKey' => 'value' },
+        expected: { 'some-key' => 'value' }
+      },
+      {
+        value: :some_value,
+        expected: :"some-value"
+      },
+      {
+        value: :SomeValue,
+        expected: :"some-value"
+      },
+      {
+        value: 'SomeValue',
+        expected: 'some-value'
+      },
+      {
+        value: :someValue,
+        expected: :"some-value"
+      },
+      {
+        value: 'someValue',
+        expected: 'some-value'
+      },
+      {
+        value: obj,
+        expected: obj
+      },
+      {
+        value: nil,
+        expected: nil
+      }
+    ]
+    scenarios.each do |s|
+      result = ActiveModelSerializers::KeyTransform.dash(s[:value])
+      assert_equal s[:expected], result
+    end
+  end
+
+  def test_underscore
+    obj = Object.new
+    scenarios = [
+      {
+        value: { :"some-key" => 'value' },
+        expected: { :some_key => 'value' }
+      },
+      {
+        value: { 'some-key' => 'value' },
+        expected: { 'some_key' => 'value' }
+      },
+      {
+        value: { :SomeKey => 'value' },
+        expected: { :some_key => 'value' }
+      },
+      {
+        value: { 'SomeKey' => 'value' },
+        expected: { 'some_key' => 'value' }
+      },
+      {
+        value: { :someKey => 'value' },
+        expected: { :some_key => 'value' }
+      },
+      {
+        value: { 'someKey' => 'value' },
+        expected: { 'some_key' => 'value' }
+      },
+      {
+        value: :"some-value",
+        expected: :some_value
+      },
+      {
+        value: :SomeValue,
+        expected: :some_value
+      },
+      {
+        value: :someValue,
+        expected: :some_value
+      },
+      {
+        value: 'some-value',
+        expected: 'some_value'
+      },
+      {
+        value: 'SomeValue',
+        expected: 'some_value'
+      },
+      {
+        value: 'someValue',
+        expected: 'some_value'
+      },
+      {
+        value: obj,
+        expected: obj
+      },
+      {
+        value: nil,
+        expected: nil
+      }
+    ]
+    scenarios.each do |s|
+      result = ActiveModelSerializers::KeyTransform.underscore(s[:value])
+      assert_equal s[:expected], result
+    end
+  end
+end

test/adapter/json/transform_test.rb

@@ -8,8 +8,8 @@ module ActiveModelSerializers
           context = Minitest::Mock.new
           context.expect(:request_url, URI)
           context.expect(:query_parameters, {})
-          context.expect(:key_transform, key_transform)
           @options = {}
+          @options[:key_transform] = key_transform if key_transform
           @options[:serialization_context] = context
         end
 
@@ -25,14 +25,14 @@ module ActiveModelSerializers
           @adapter = ActiveModelSerializers::Adapter::Json.new(serializer)
         end
 
-        def test_key_transform_default
+        def test_transform_default
           mock_request
           assert_equal({
             blog: { id: 1, special_attribute: 'neat', articles: nil }
           }, @adapter.serializable_hash(@options))
         end
 
-        def test_key_transform_global_config
+        def test_transform_global_config
           mock_request
           result = with_config(key_transform: :camel_lower) do
             @adapter.serializable_hash(@options)
@@ -42,7 +42,7 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_key_transform_serialization_ctx_overrides_global_config
+        def test_transform_serialization_ctx_overrides_global_config
           mock_request(:camel)
           result = with_config(key_transform: :camel_lower) do
             @adapter.serializable_hash(@options)
@@ -52,7 +52,7 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_key_transform_undefined
+        def test_transform_undefined
           mock_request(:blam)
           result = nil
           assert_raises NoMethodError do
@@ -60,28 +60,28 @@ module ActiveModelSerializers
           end
         end
 
-        def test_key_transform_dashed
+        def test_transform_dash
-          mock_request(:dashed)
+          mock_request(:dash)
           assert_equal({
             blog: { id: 1, :"special-attribute" => 'neat', articles: nil }
           }, @adapter.serializable_hash(@options))
         end
 
-        def test_key_transform_unaltered
+        def test_transform_unaltered
           mock_request(:unaltered)
           assert_equal({
             blog: { id: 1, special_attribute: 'neat', articles: nil }
           }, @adapter.serializable_hash(@options))
         end
 
-        def test_key_transform_camel
+        def test_transform_camel
           mock_request(:camel)
           assert_equal({
             Blog: { Id: 1, SpecialAttribute: 'neat', Articles: nil }
           }, @adapter.serializable_hash(@options))
         end
 
-        def test_key_transform_camel_lower
+        def test_transform_camel_lower
           mock_request(:camel_lower)
           assert_equal({
             blog: { id: 1, specialAttribute: 'neat', articles: nil }

test/adapter/json_api/has_many_test.rb

@@ -129,7 +129,7 @@ module ActiveModelSerializers
           assert_equal({
             data: {
               id: '1',
-              type: 'virtual_values',
+              type: 'virtual-values',
               relationships: {
                 maker: { data: { id: 1 } },
                 reviews: { data: [{ id: 1 }, { id: 2 }] }

test/adapter/json_api/has_one_test.rb

@@ -63,7 +63,7 @@ module ActiveModelSerializers
           expected = {
             data: {
               id: '1',
-              type: 'virtual_values',
+              type: 'virtual-values',
               relationships: {
                 maker: { data: { id: 1 } },
                 reviews: { data: [{ id: 1 }, { id: 2 }] }

test/adapter/json_api/linked_test.rb

@@ -216,7 +216,7 @@ module ActiveModelSerializers
           expected = {
             related: {
               data: [{
-                type: 'spam_unrelated_links',
+                type: 'spam-unrelated-links',
                 id: '456'
               }]
             }
@@ -366,12 +366,12 @@ module ActiveModelSerializers
             adapter: :json_api,
             include: '*').serializable_hash
           expected = [
-            type: 'nested_posts', id: '2',
+            type: 'nested-posts', id: '2',
             relationships: {
-              nested_posts: {
+              :"nested-posts" => {
                 data: [
-                  { type: 'nested_posts', id: '1' },
+                  { type: 'nested-posts', id: '1' },
-                  { type: 'nested_posts', id: '2' }
+                  { type: 'nested-posts', id: '2' }
                 ]
               }
             }

test/adapter/json_api/links_test.rb

@@ -80,10 +80,10 @@ module ActiveModelSerializers
               }
             },
             author: 'http://example.com/link_authors/1337',
-            link_authors: 'http://example.com/link_authors',
+            :"link-authors" => 'http://example.com/link_authors',
             resource: 'http://example.com/resource',
             posts: 'http://example.com/link_authors/1337/posts',
-            yet_another: 'http://example.com/resource/1337'
+            :"yet-another" => 'http://example.com/resource/1337'
           }
           assert_equal(expected, hash[:data][:links])
         end

test/adapter/json_api/pagination_links_test.rb

@@ -25,7 +25,6 @@ module ActiveModelSerializers
           context = Minitest::Mock.new
           context.expect(:request_url, original_url)
           context.expect(:query_parameters, query_parameters)
-          context.expect(:key_transform, nil)
           @options = {}
           @options[:serialization_context] = context
         end

test/adapter/json_api/relationship_test.rb

@@ -151,11 +151,8 @@ module ActiveModelSerializers
         private
 
         def test_relationship(expected, params = {})
-          options = params.fetch(:options, {})
-          links = params.fetch(:links, {})
-          meta = params[:meta]
           parent_serializer = AuthorSerializer.new(@author)
-          relationship = Relationship.new(parent_serializer, @serializer, options, links, meta)
+          relationship = Relationship.new(parent_serializer, @serializer, nil, params)
           assert_equal(expected, relationship.as_json)
         end
       end

test/adapter/json_api/resource_identifier_test.rb

@@ -22,7 +22,7 @@ module ActiveModelSerializers
         end
 
         def test_defined_type
-          test_type(WithDefinedTypeSerializer, 'with_defined_type')
+          test_type(WithDefinedTypeSerializer, 'with-defined-type')
         end
 
         def test_singular_type
@@ -58,7 +58,7 @@ module ActiveModelSerializers
 
         def test_type(serializer_class, expected_type)
           serializer = serializer_class.new(@model)
-          resource_identifier = ResourceIdentifier.new(serializer)
+          resource_identifier = ResourceIdentifier.new(serializer, nil)
           expected = {
             id: @model.id.to_s,
             type: expected_type
@@ -69,7 +69,7 @@ module ActiveModelSerializers
 
         def test_id(serializer_class, id)
           serializer = serializer_class.new(@model)
-          resource_identifier = ResourceIdentifier.new(serializer)
+          resource_identifier = ResourceIdentifier.new(serializer, nil)
           inflection = ActiveModelSerializers.config.jsonapi_resource_type
           type = @model.class.model_name.send(inflection)
           expected = {

test/adapter/json_api/resource_meta_test.rb

@@ -54,7 +54,7 @@ module ActiveModel
               adapter: :json_api
             ).serializable_hash
             expected = {
-              comments_count: @post.comments.count
+              :"comments-count" => @post.comments.count
             }
             assert_equal(expected, hash[:data][:meta])
           end
@@ -69,8 +69,8 @@ module ActiveModel
             ).serializable_hash
             expected = {
               :data => [
-                { :id => '1337', :type => 'posts', :meta => { :comments_count => 0 } },
+                { :id => '1337', :type => 'posts', :meta => { :"comments-count" => 0 } },
-                { :id => '1339', :type => 'posts', :meta => { :comments_count => 1 } }
+                { :id => '1339', :type => 'posts', :meta => { :"comments-count" => 1 } }
               ]
             }
             assert_equal(expected, hash)

test/adapter/json_api/transform_test.rb

@@ -36,13 +36,13 @@ module ActiveModelSerializers
           belongs_to :author
         end
 
-        def mock_request(key_transform = nil)
+        def mock_request(transform = nil)
           context = Minitest::Mock.new
           context.expect(:request_url, URI)
           context.expect(:query_parameters, {})
-          context.expect(:key_transform, key_transform)
           context.expect(:url_helpers, Rails.application.routes.url_helpers)
           @options = {}
+          @options[:key_transform] = transform if transform
           @options[:serialization_context] = context
         end
 
@@ -64,7 +64,7 @@ module ActiveModelSerializers
           @comment2.post = @post
         end
 
-        def test_success_document_key_transform_default
+        def test_success_document_transform_default
           mock_request
           serializer = PostSerializer.new(@post)
           adapter = ActiveModelSerializers::Adapter::JsonApi.new(serializer)
@@ -98,7 +98,7 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_success_document_key_transform_global_config
+        def test_success_document_transform_global_config
           mock_request
           result = with_config(key_transform: :camel_lower) do
             serializer = PostSerializer.new(@post)
@@ -134,7 +134,7 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_success_doc_key_transform_serialization_ctx_overrides_global
+        def test_success_doc_transform_serialization_ctx_overrides_global
           mock_request(:camel)
           result = with_config(key_transform: :camel_lower) do
             serializer = PostSerializer.new(@post)
@@ -144,7 +144,7 @@ module ActiveModelSerializers
           assert_equal({
             Data: {
               Id: '1337',
-              Type: 'posts',
+              Type: 'Posts',
               Attributes: {
                 Title: 'Title 1',
                 Body: 'Body 1',
@@ -152,12 +152,12 @@ module ActiveModelSerializers
               },
               Relationships: {
                 Author: {
-                  Data: { Id: '1', Type: 'authors' }
+                  Data: { Id: '1', Type: 'Authors' }
                 },
                 Comments: {
                   Data: [
-                    { Id: '7', Type: 'comments' },
+                    { Id: '7', Type: 'Comments' },
-                    { Id: '12', Type: 'comments' }
+                    { Id: '12', Type: 'Comments' }
                 ] }
               },
               Links: {
@@ -170,8 +170,8 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_success_document_key_transform_dashed
+        def test_success_document_transform_dash
-          mock_request(:dashed)
+          mock_request(:dash)
           serializer = PostSerializer.new(@post)
           adapter = ActiveModelSerializers::Adapter::JsonApi.new(serializer)
           result = adapter.serializable_hash(@options)
@@ -204,7 +204,7 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_success_document_key_transform_unaltered
+        def test_success_document_transform_unaltered
           mock_request(:unaltered)
           serializer = PostSerializer.new(@post)
           adapter = ActiveModelSerializers::Adapter::JsonApi.new(serializer)
@@ -238,7 +238,7 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_success_document_key_transform_undefined
+        def test_success_document_transform_undefined
           mock_request(:zoot)
           serializer = PostSerializer.new(@post)
           adapter = ActiveModelSerializers::Adapter::JsonApi.new(serializer)
@@ -247,7 +247,7 @@ module ActiveModelSerializers
           end
         end
 
-        def test_success_document_key_transform_camel
+        def test_success_document_transform_camel
           mock_request(:camel)
           serializer = PostSerializer.new(@post)
           adapter = ActiveModelSerializers::Adapter::JsonApi.new(serializer)
@@ -255,7 +255,7 @@ module ActiveModelSerializers
           assert_equal({
             Data: {
               Id: '1337',
-              Type: 'posts',
+              Type: 'Posts',
               Attributes: {
                 Title: 'Title 1',
                 Body: 'Body 1',
@@ -263,12 +263,12 @@ module ActiveModelSerializers
               },
               Relationships: {
                 Author: {
-                  Data: { Id: '1', Type: 'authors' }
+                  Data: { Id: '1', Type: 'Authors' }
                 },
                 Comments: {
                   Data: [
-                    { Id: '7', Type: 'comments' },
+                    { Id: '7', Type: 'Comments' },
-                    { Id: '12', Type: 'comments' }
+                    { Id: '12', Type: 'Comments' }
                 ] }
               },
               Links: {
@@ -281,7 +281,7 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_success_document_key_transform_camel_lower
+        def test_success_document_transform_camel_lower
           mock_request(:camel_lower)
           serializer = PostSerializer.new(@post)
           adapter = ActiveModelSerializers::Adapter::JsonApi.new(serializer)
@@ -315,7 +315,7 @@ module ActiveModelSerializers
           }, result)
         end
 
-        def test_error_document_key_transform_default
+        def test_error_document_transform_default
           mock_request
           resource = ModelWithErrors.new
           resource.errors.add(:published_at, 'must be in the future')
@@ -327,7 +327,7 @@ module ActiveModelSerializers
             { :errors =>
               [
                 {
-                  :source => { :pointer => '/data/attributes/published_at' },
+                  :source => { :pointer => '/data/attributes/published-at' },
                   :detail => 'must be in the future' },
                 {
                   :source => { :pointer => '/data/attributes/title' },
@@ -338,7 +338,7 @@ module ActiveModelSerializers
           assert_equal expected_errors_object, result
         end
 
-        def test_error_document_key_transform_global_config
+        def test_error_document_transform_global_config
           mock_request
           result = with_config(key_transform: :camel) do
             resource = ModelWithErrors.new
@@ -352,11 +352,11 @@ module ActiveModelSerializers
             { :Errors =>
               [
                 {
-                  :Source => { :Pointer => '/data/attributes/published_at' },
+                  :Source => { :Pointer => '/data/attributes/PublishedAt' },
                   :Detail => 'must be in the future'
                 },
                 {
-                  :Source => { :Pointer => '/data/attributes/title' },
+                  :Source => { :Pointer => '/data/attributes/Title' },
                   :Detail => 'must be longer'
                 }
               ]
@@ -364,7 +364,7 @@ module ActiveModelSerializers
           assert_equal expected_errors_object, result
         end
 
-        def test_error_document_key_transform_serialization_ctx_overrides_global
+        def test_error_document_transform_serialization_ctx_overrides_global
           mock_request(:camel)
           result = with_config(key_transform: :camel_lower) do
             resource = ModelWithErrors.new
@@ -378,11 +378,11 @@ module ActiveModelSerializers
             { :Errors =>
               [
                 {
-                  :Source => { :Pointer => '/data/attributes/published_at' },
+                  :Source => { :Pointer => '/data/attributes/PublishedAt' },
                   :Detail => 'must be in the future'
                 },
                 {
-                  :Source => { :Pointer => '/data/attributes/title' },
+                  :Source => { :Pointer => '/data/attributes/Title' },
                   :Detail => 'must be longer'
                 }
               ]
@@ -390,8 +390,8 @@ module ActiveModelSerializers
           assert_equal expected_errors_object, result
         end
 
-        def test_error_document_key_transform_dashed
+        def test_error_document_transform_dash
-          mock_request(:dashed)
+          mock_request(:dash)
 
           resource = ModelWithErrors.new
           resource.errors.add(:published_at, 'must be in the future')
@@ -405,7 +405,7 @@ module ActiveModelSerializers
             { :errors =>
               [
                 {
-                  :source => { :pointer => '/data/attributes/published_at' },
+                  :source => { :pointer => '/data/attributes/published-at' },
                   :detail => 'must be in the future'
                 },
                 {
@@ -417,7 +417,7 @@ module ActiveModelSerializers
           assert_equal expected_errors_object, result
         end
 
-        def test_error_document_key_transform_unaltered
+        def test_error_document_transform_unaltered
           mock_request(:unaltered)
 
           resource = ModelWithErrors.new
@@ -438,7 +438,7 @@ module ActiveModelSerializers
           assert_equal expected_errors_object, result
         end
 
-        def test_error_document_key_transform_undefined
+        def test_error_document_transform_undefined
           mock_request(:krazy)
 
           resource = ModelWithErrors.new
@@ -453,7 +453,7 @@ module ActiveModelSerializers
           end
         end
 
-        def test_error_document_key_transform_camel
+        def test_error_document_transform_camel
           mock_request(:camel)
 
           resource = ModelWithErrors.new
@@ -467,14 +467,14 @@ module ActiveModelSerializers
           expected_errors_object =
             { :Errors =>
               [
-                { :Source => { :Pointer => '/data/attributes/published_at' }, :Detail => 'must be in the future' },
+                { :Source => { :Pointer => '/data/attributes/PublishedAt' }, :Detail => 'must be in the future' },
-                { :Source => { :Pointer => '/data/attributes/title' }, :Detail => 'must be longer' }
+                { :Source => { :Pointer => '/data/attributes/Title' }, :Detail => 'must be longer' }
               ]
           }
           assert_equal expected_errors_object, result
         end
 
-        def test_error_document_key_transform_camel_lower
+        def test_error_document_transform_camel_lower
           mock_request(:camel_lower)
 
           resource = ModelWithErrors.new
@@ -488,7 +488,7 @@ module ActiveModelSerializers
           expected_errors_object =
             { :errors =>
               [
-                { :source => { :pointer => '/data/attributes/published_at' }, :detail => 'must be in the future' },
+                { :source => { :pointer => '/data/attributes/publishedAt' }, :detail => 'must be in the future' },
                 { :source => { :pointer => '/data/attributes/title' }, :detail => 'must be longer' }
               ]
           }

test/benchmark/bm_caching.rb

@@ -70,7 +70,8 @@ class ApiAssertion
           },
           'author' => {
             'id' => 42,
-            'name' => 'Joao Moura.'
+            'first_name' => 'Joao',
+            'last_name' => 'Moura'
           }
         }
     }

test/benchmark/bm_transform.rb

@@ -0,0 +1,34 @@
+require_relative './benchmarking_support'
+require_relative './app'
+
+time = 10
+disable_gc = true
+ActiveModelSerializers.config.key_transform = :unaltered
+comments = (0..50).map do |i|
+  Comment.new(id: i, body: 'ZOMG A COMMENT')
+end
+author = Author.new(id: 42, first_name: 'Joao', last_name: 'Moura')
+post = Post.new(id: 1337, title: 'New Post', blog: nil, body: 'Body', comments: comments, author: author)
+serializer = PostSerializer.new(post)
+adapter = ActiveModelSerializers::Adapter::JsonApi.new(serializer)
+serialization = adapter.as_json
+
+Benchmark.ams('camel', time: time, disable_gc: disable_gc) do
+  ActiveModelSerializers::KeyTransform.camel(serialization)
+end
+
+Benchmark.ams('camel_lower', time: time, disable_gc: disable_gc) do
+  ActiveModelSerializers::KeyTransform.camel_lower(serialization)
+end
+
+Benchmark.ams('dash', time: time, disable_gc: disable_gc) do
+  ActiveModelSerializers::KeyTransform.dash(serialization)
+end
+
+Benchmark.ams('unaltered', time: time, disable_gc: disable_gc) do
+  ActiveModelSerializers::KeyTransform.unaltered(serialization)
+end
+
+Benchmark.ams('underscore', time: time, disable_gc: disable_gc) do
+  ActiveModelSerializers::KeyTransform.underscore(serialization)
+end

test/benchmark/controllers.rb

@@ -8,7 +8,7 @@ class PostController < ActionController::Base
       else
         comments = [Comment.new(id: 1, body: 'ZOMG A COMMENT')]
       end
-      author = Author.new(id: 42, name: 'Joao Moura.')
+      author = Author.new(id: 42, first_name: 'Joao', last_name: 'Moura')
       Post.new(id: 1337, title: 'New Post', blog: nil, body: 'Body', comments: comments, author: author)
     end
 

test/benchmark/fixtures.rb

@@ -1,6 +1,6 @@
 Rails.configuration.serializers = []
 class AuthorSerializer < ActiveModel::Serializer
-  attributes :id, :name
+  attributes :id, :first_name, :last_name
 
   has_many :posts, embed: :ids
   has_one :bio
@@ -27,6 +27,15 @@ class PostSerializer < ActiveModel::Serializer
   belongs_to :blog, serializer: BlogSerializer
   belongs_to :author, serializer: AuthorSerializer
 
+  link(:post_authors) { 'https://example.com/post_authors' }
+
+  meta do
+    {
+      rating: 5,
+      favorite_count: 10
+    }
+  end
+
   def blog
     Blog.new(id: 999, name: 'Custom blog')
   end
@@ -34,7 +43,7 @@ end
 Rails.configuration.serializers << PostSerializer
 
 class CachingAuthorSerializer < AuthorSerializer
-  cache key: 'writer', only: [:name], skip_digest: true
+  cache key: 'writer', only: [:first_name, :last_name], skip_digest: true
 end
 Rails.configuration.serializers << CachingAuthorSerializer
 
@@ -63,7 +72,8 @@ if ENV['ENABLE_ACTIVE_RECORD'] == 'true'
       t.timestamps null: false
     end
     create_table :authors, force: true do |t|
-      t.string :name
+      t.string :first_name
+      t.string :last_name
       t.timestamps null: false
     end
     create_table :posts, force: true do |t|
@@ -144,7 +154,7 @@ else
   end
 
   class Author < BenchmarkModel
-    attr_accessor :id, :name, :posts
+    attr_accessor :id, :first_name, :last_name, :posts
   end
 
   class Post < BenchmarkModel