Encapsulate serialization in ActiveModel::Serializer::Builder

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

Author: bf4

lib/action_controller/serialization.rb

@@ -6,7 +6,7 @@ module Serialization
 
     include ActionController::Renderers
 
-    ADAPTER_OPTION_KEYS = [:include, :fields, :root, :adapter]
+    ADAPTER_OPTION_KEYS = ActiveModel::Serializer::Builder::ADAPTER_OPTION_KEYS
 
     included do
       class_attribute :_serialization_scope
@@ -18,46 +18,46 @@ def serialization_scope
         respond_to?(_serialization_scope, true)
     end
 
+    # Deprecated
     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)
-      end
-
-      @_serializer
+      fail ActiveModel::Serializer::Error, "ActionController::Serialization##{__method__} has been removed. "\
+        "Please use ActiveSupport::Serializer#build instead"
     end
 
+    # Deprecated
     def use_adapter?
-      !(@_adapter_opts.key?(:adapter) && !@_adapter_opts[:adapter])
+      fail ActiveModel::Serializer::Error, "ActionController::Serialization##{__method__} has been removed. "\
+        "Please use ActiveSupport::Serializer#build instead"
     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
-
-          # omg hax
-          object = serializer.new(resource, @_serializer_opts)
-          adapter = ActiveModel::Serializer::Adapter.create(object, @_adapter_opts)
+        builder = ActiveModel::Serializer::Builder.new(resource, options)
+        if builder.serializer?
+          builder.serialization_scope ||= serialization_scope
+          builder.serialization_scope_name = _serialization_scope
+          adapter = builder.adapter
           super(adapter, options)
         else
           super(resource, options)
         end
       end
     end
 
+    # Tries to rescue the exception by looking up and calling a registered handler.
+    # 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

@@ -2,10 +2,12 @@
 
 module ActiveModel
   class Serializer
+    Error = Class.new(StandardError)
     extend ActiveSupport::Autoload
     autoload :Configuration
     autoload :ArraySerializer
     autoload :Adapter
+    autoload :Builder
     include Configuration
 
     class << self
@@ -28,6 +30,13 @@ def self.inherited(base)
       base._urls = []
     end
 
+    # Primary interface to building a serializer (with adapter)
+    def self.build(resource, options = {})
+      builder = Builder.new(resource, options)
+      yield builder if block_given?
+      builder.adapter
+    end
+
     def self.attributes(*attrs)
       attrs = attrs.first if attrs.first.class == Array
       @_attributes.concat attrs

lib/active_model/serializer/builder.rb

@@ -0,0 +1,69 @@
+require "set"
+module ActiveModel
+  class Serializer
+    class Builder
+      extend ActiveSupport::Autoload
+
+      ADAPTER_OPTION_KEYS = Set.new([:include, :fields, :root, :adapter])
+
+      def initialize(resource, options = {})
+        @resource = resource
+        @adapter_opts, @serializer_opts =
+          options.partition { |k, _| ADAPTER_OPTION_KEYS.include? k }.map { |h| Hash[h] }
+      end
+
+      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 MyController < 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

@@ -136,10 +136,7 @@ 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)
@@ -405,6 +402,20 @@ def test_cache_expiration_on_update
         assert_equal 'application/json', @response.content_type
         assert_equal expected.to_json, @response.body
       end
+
+      def test_fail_calling_use_adapter_on_controller_instance
+        controller = MyController.new
+        assert_raises(ActiveModel::Serializer::Error) {
+          controller.use_adapter?
+        }
+      end
+
+      def test_fail_calling_get_serializer__on_controller_instance
+        controller = MyController.new
+        assert_raises(ActiveModel::Serializer::Error) {
+          controller.get_serializer(Class.new)
+        }
+      end
     end
   end
 end

test/serializers/cache_test.rb

@@ -117,10 +117,7 @@ def test_fragment_fetch_with_virtual_associations
 
       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

@@ -94,11 +94,9 @@ 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::Json.new(serializer, adapter_opts)
+        options = options.merge(adapter: :json, serializer: AlternateBlogSerializer)
+        builder = ActiveModel::Serializer::Builder.new(@blog, options)
+        builder.adapter
       end
     end
   end