Encapsulate serialization in ActiveModel::Serializer::Builder

Usage: ActiveModel::Serializer.build(resource, options)

Author: bf4

lib/action_controller/serialization.rb

@@ -6,7 +6,8 @@ module Serialization
 
     include ActionController::Renderers
 
-    ADAPTER_OPTION_KEYS = [:include, :fields, :adapter]
+    # Deprecated
+    ADAPTER_OPTION_KEYS = ActiveModel::Serializer::Builder::ADAPTER_OPTION_KEYS
 
     included do
       class_attribute :_serialization_scope
@@ -18,47 +19,55 @@ def serialization_scope
         respond_to?(_serialization_scope, true)
     end
 
-    def get_serializer(resource)
-      @_serializer ||= @_serializer_opts.delete(:serializer)
-      @_serializer ||= ActiveModel::Serializer.serializer_for(resource)
-
-      if @_serializer_opts.key?(:each_serializer)
-        @_serializer_opts[:serializer] = @_serializer_opts.delete(:each_serializer)
+    def get_serializer(resource, options = {})
+      if ! use_adapter?
+        warn "ActionController::Serialization#use_adapter? has been removed. "\
+          "Please pass 'adapter: false' or see ActiveSupport::Serializer.build"
+        options[:adapter] = false
+      end
+      serializable_resource = ActiveModel::Serializer::build(resource, options) do |builder|
+        if builder.serializer?
+          builder.serialization_scope ||= serialization_scope
+          builder.serialization_scope_name = _serialization_scope
+          begin
+            builder.adapter
+          rescue ActiveModel::Serializer::ArraySerializer::NoSerializerError
+            resource
+          end
+        else
+          resource
+        end
       end
-
-      @_serializer
     end
 
+    # Deprecated
     def use_adapter?
-      !(@_adapter_opts.key?(:adapter) && !@_adapter_opts[:adapter])
+      true
     end
 
     [:_render_option_json, :_render_with_renderer_json].each do |renderer_method|
       define_method renderer_method do |resource, options|
-        @_adapter_opts, @_serializer_opts =
-          options.partition { |k, _| ADAPTER_OPTION_KEYS.include? k }.map { |h| Hash[h] }
-
-        if use_adapter? && (serializer = get_serializer(resource))
-          @_serializer_opts[:scope] ||= serialization_scope
-          @_serializer_opts[:scope_name] = _serialization_scope
-
-          begin
-            serialized = serializer.new(resource, @_serializer_opts)
-          rescue ActiveModel::Serializer::ArraySerializer::NoSerializerError
-          else
-            resource = ActiveModel::Serializer::Adapter.create(serialized, @_adapter_opts)
-          end
-        end
-
-        super(resource, options)
+        serializable_resource = get_serializer(resource, options)
+        super(serializable_resource, options)
       end
     end
 
+    # Tries to rescue the exception by looking up and calling a registered handler.
+    #
+    # Possibly Deprecated
+    # TODO: Either Decorate 'exception' and define #handle_error where it is serialized
+    # For example:
+    #   class ExceptionModel
+    #     include ActiveModel::Serialization
+    #     def initialize(exception)
+    #     # etc
+    #   end
+    #   def handle_error(exception)
+    #     exception_model = ActiveModel::Serializer.build_exception_model({ errors: ['Internal Server Error'] })
+    #     render json: exception_model, status: :internal_server_error
+    #   end
+    # OR remove method as it doesn't do anything right now.
     def rescue_with_handler(exception)
-      @_serializer = nil
-      @_serializer_opts = nil
-      @_adapter_opts = nil
-
       super(exception)
     end
 

lib/active_model/serializer.rb

@@ -6,6 +6,7 @@ class Serializer
     autoload :Configuration
     autoload :ArraySerializer
     autoload :Adapter
+    autoload :Builder
     include Configuration
 
     class << self
@@ -31,6 +32,18 @@ def self.inherited(base)
       base._cache_digest = Digest::MD5.hexdigest(serializer_file.read)
     end
 
+    # Primary interface to building a serializer (with adapter)
+    # If no block is given, returns the builder, ready for #as_json/#to_json/#serializable_hash
+    # Otherwise, yields the builder and returns the contents of the block
+    def self.build(resource, options = {})
+      builder = Builder.new(resource, options)
+      if block_given?
+        yield builder
+     else
+        builder
+      end
+    end
+
     def self.attributes(*attrs)
       attrs = attrs.first if attrs.first.class == Array
       @_attributes.concat attrs

lib/active_model/serializer/builder.rb

@@ -0,0 +1,71 @@
+require "set"
+module ActiveModel
+  class Serializer
+    class Builder
+      extend ActiveSupport::Autoload
+
+      ADAPTER_OPTION_KEYS = Set.new([:include, :fields, :adapter])
+
+      def initialize(resource, options = {})
+        @resource = resource
+        @adapter_opts, @serializer_opts =
+          options.partition { |k, _| ADAPTER_OPTION_KEYS.include? k }.map { |h| Hash[h] }
+      end
+
+      delegate :serializable_hash, :as_json, :to_json, to: :adapter
+
+      def serialization_scope=(scope)
+        serializer_opts[:scope] = scope
+      end
+
+      def serialization_scope
+        serializer_opts[:scope]
+      end
+
+      def serialization_scope_name=(scope_name)
+        serializer_opts[:scope_name] = scope_name
+      end
+
+      def adapter
+        @adapter ||= ActiveModel::Serializer::Adapter.create(serializer_instance, adapter_opts)
+      end
+      alias_method :adapter_instance, :adapter
+
+      def serializer_instance
+        @serializer_instance ||= serializer.new(resource, serializer_opts)
+      end
+
+      # Get serializer either explicitly :serializer or implicitly from resource
+      # Remove :serializer key from serializer_opts
+      # Replace :serializer key with :each_serializer if present
+      def serializer
+        @serializer ||=
+          begin
+            @serializer = serializer_opts.delete(:serializer)
+            @serializer ||= ActiveModel::Serializer.serializer_for(resource)
+
+            if serializer_opts.key?(:each_serializer)
+              serializer_opts[:serializer] = serializer_opts.delete(:each_serializer)
+            end
+            @serializer
+          end
+      end
+      alias_method :serializer_class, :serializer
+
+      # True when no explicit adapter given, or explicit appear is truthy (non-nil)
+      # False when explicit adapter is falsy (nil or false)
+      def use_adapter?
+        !(adapter_opts.key?(:adapter) && !adapter_opts[:adapter])
+      end
+
+      def serializer?
+        use_adapter? && !!(serializer)
+      end
+
+      private
+
+      attr_reader :resource, :adapter_opts, :serializer_opts
+
+    end
+  end
+end

test/action_controller/rescue_from_test.rb

@@ -7,8 +7,8 @@ class RescueFromTestController < ActionController::Base
         rescue_from Exception, with: :handle_error
 
         def render_using_raise_error_serializer
-          @profile = Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })
-          render json: [@profile], serializer: RaiseErrorSerializer
+          profile = Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })
+          render json: [profile], serializer: RaiseErrorSerializer
         end
 
         def handle_error(exception)
@@ -25,7 +25,7 @@ def test_rescue_from
           errors: ['Internal Server Error']
         }.to_json
 
-        assert_equal expected, @response.body
+        assert_equal expected, response.body
       end
     end
   end

test/action_controller/serialization_test.rb

@@ -4,6 +4,7 @@
 module ActionController
   module Serialization
     class ImplicitSerializerTest < ActionController::TestCase
+      include ActiveSupport::Testing::Stream
       class ImplicitSerializationTestController < ActionController::Base
         def render_using_implicit_serializer
           @profile = Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })
@@ -120,10 +121,7 @@ def render_fragment_changed_object_with_relationship
 
         private
         def generate_cached_serializer(obj)
-          serializer_class = ActiveModel::Serializer.serializer_for(obj)
-          serializer = serializer_class.new(obj)
-          adapter = ActiveModel::Serializer.adapter.new(serializer)
-          adapter.to_json
+          ActiveModel::Serializer.build(obj).to_json
         end
 
         def with_adapter(adapter)
@@ -356,6 +354,28 @@ def test_cache_expiration_on_update
         assert_equal 'application/json', @response.content_type
         assert_equal expected.to_json, @response.body
       end
+
+      def test_warn_overridding_use_adapter_as_falsy_on_controller_instance
+        controller = Class.new(ImplicitSerializationTestController) {
+          def use_adapter?
+            false
+          end
+        }.new
+        assert_match /adapter: false/, (capture(:stderr) {
+          controller.get_serializer(@profile)
+        })
+      end
+
+      def test_dont_warn_overridding_use_adapter_as_truthy_on_controller_instance
+        controller = Class.new(ImplicitSerializationTestController) {
+          def use_adapter?
+            true
+          end
+        }.new
+        assert_equal "", (capture(:stderr) {
+          controller.get_serializer(@profile)
+        })
+      end
     end
   end
 end

test/serializer_builder_test.rb

@@ -0,0 +1,29 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class BuilderTest < Minitest::Test
+      def setup
+        @resource = Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })
+        @serializer = ProfileSerializer.new(@resource)
+        @adapter = ActiveModel::Serializer::Adapter.create(@serializer)
+        @builder = ActiveModel::Serializer.build(@resource)
+      end
+
+      def test_builder_delegates_serializable_hash_to_the_adapter
+        options = nil
+        assert_equal @adapter.serializable_hash(options), @builder.serializable_hash(options)
+      end
+
+      def test_builder_delegates_to_json_to_the_adapter
+        options = nil
+        assert_equal @adapter.to_json(options), @builder.to_json(options)
+      end
+
+      def test_builder_delegates_as_json_to_the_adapter
+        options = nil
+        assert_equal @adapter.as_json(options), @builder.as_json(options)
+      end
+    end
+  end
+end

test/serializers/cache_test.rb

@@ -127,10 +127,7 @@ def _cache_digest_definition
 
       private
       def render_object_with_cache(obj)
-        serializer_class = ActiveModel::Serializer.serializer_for(obj)
-        serializer = serializer_class.new(obj)
-        adapter = ActiveModel::Serializer.adapter.new(serializer)
-        adapter.serializable_hash
+        ActiveModel::Serializer.build(obj).serializable_hash
       end
     end
   end

test/serializers/meta_test.rb

@@ -99,11 +99,8 @@ def test_meta_is_present_on_arrays_with_root
       private
 
       def load_adapter(options)
-        adapter_opts, serializer_opts =
-          options.partition { |k, _| ActionController::Serialization::ADAPTER_OPTION_KEYS.include? k }.map { |h| Hash[h] }
-
-        serializer = AlternateBlogSerializer.new(@blog, serializer_opts)
-        ActiveModel::Serializer::Adapter::FlattenJson.new(serializer, adapter_opts)
+        options = options.merge(adapter: :flatten_json, serializer: AlternateBlogSerializer)
+        ActiveModel::Serializer.build(@blog, options)
       end
     end
   end

test/test_helper.rb

@@ -13,6 +13,55 @@
 
 require 'active_model_serializers'
 
+# Use cleaner stream testing interface from Rails 5 if available
+# see https://github.com/rails/rails/blob/29959eb59d/activesupport/lib/active_support/testing/stream.rb
+begin
+  require "active_support/testing/stream"
+rescue LoadError
+  module ActiveSupport
+    module Testing
+      module Stream #:nodoc:
+        private
+
+        def silence_stream(stream)
+          old_stream = stream.dup
+          stream.reopen(IO::NULL)
+          stream.sync = true
+          yield
+        ensure
+          stream.reopen(old_stream)
+          old_stream.close
+        end
+
+        def quietly
+          silence_stream(STDOUT) do
+            silence_stream(STDERR) do
+              yield
+            end
+          end
+        end
+
+        def capture(stream)
+          stream = stream.to_s
+          captured_stream = Tempfile.new(stream)
+          stream_io = eval("$#{stream}")
+          origin_stream = stream_io.dup
+          stream_io.reopen(captured_stream)
+
+          yield
+
+          stream_io.rewind
+          return captured_stream.read
+        ensure
+          captured_stream.close
+          captured_stream.unlink
+          stream_io.reopen(origin_stream)
+        end
+      end
+    end
+  end
+end
+
 class Foo < Rails::Application
   if Rails::VERSION::MAJOR >= 4
     config.eager_load = false