sparse fieldsets

lib/action_controller/serialization.rb

@@ -6,7 +6,7 @@ module Serialization
 
     include ActionController::Renderers
 
-    ADAPTER_OPTION_KEYS = [:include, :root, :adapter]
+    ADAPTER_OPTION_KEYS = [:include, :fields, :root, :adapter]
 
     def get_serializer(resource)
       @_serializer ||= @_serializer_opts.delete(:serializer)

lib/active_model/serializer.rb

@@ -130,7 +130,14 @@ def json_key
     end
 
     def attributes(options = {})
-      self.class._attributes.dup.each_with_object({}) do |name, hash|
+      attributes =
+        if options[:fields]
+          self.class._attributes & options[:fields]
+        else
+          self.class._attributes.dup
+        end
+
+      attributes.each_with_object({}) do |name, hash|
         hash[name] = send(name)
       end
     end

lib/active_model/serializer/adapter/json_api.rb

@@ -7,14 +7,20 @@ def initialize(serializer, options = {})
           serializer.root = true
           @hash = {}
           @top = @options.fetch(:top) { @hash }
+
+          if fields = options.delete(:fields)
+            @fieldset = ActiveModel::Serializer::Fieldset.new(fields, serializer.json_key)
+          else
+            @fieldset = options[:fieldset]
+          end
         end
 
         def serializable_hash(options = {})
           @root = (@options[:root] || serializer.json_key.to_s.pluralize).to_sym
 
           if serializer.respond_to?(:each)
             @hash[@root] = serializer.map do |s|
-              self.class.new(s, @options.merge(top: @top)).serializable_hash[@root]
+              self.class.new(s, @options.merge(top: @top, fieldset: @fieldset)).serializable_hash[@root]
             end
           else
             @hash[@root] = attributes_for_serializer(serializer, @options)
@@ -79,15 +85,18 @@ def add_linked(resource_name, serializer, parent = nil)
           end if include_nested_assoc? resource_path
         end
 
+
         def attributes_for_serializer(serializer, options)
           if serializer.respond_to?(:each)
             result = []
             serializer.each do |object|
+              options[:fields] = @fieldset && @fieldset.fields_for(serializer)
               attributes = object.attributes(options)
               attributes[:id] = attributes[:id].to_s if attributes[:id]
               result << attributes
             end
           else
+            options[:fields] = @fieldset && @fieldset.fields_for(serializer)
             result = serializer.attributes(options)
             result[:id] = result[:id].to_s if result[:id]
           end

lib/active_model/serializer/fieldset.rb

@@ -0,0 +1,40 @@
+module ActiveModel
+  class Serializer
+    class Fieldset
+
+      def initialize(fields, root = nil)
+        @root       = root
+        @raw_fields = fields
+      end
+
+      def fields
+        @fields ||= parsed_fields
+      end
+
+      def fields_for(serializer)
+        key = serializer.json_key || serializer.class.root_name
+        fields[key.to_sym]
+      end
+
+    private
+
+      attr_reader :raw_fields, :root
+
+      def parsed_fields
+        if raw_fields.is_a?(Hash)
+          raw_fields.inject({}) { |h,(k,v)| h[k.to_sym] = v.map(&:to_sym); h}
+        elsif raw_fields.is_a?(Array)
+          if root.nil?
+            raise ArgumentError, 'The root argument must be specified if the fileds argument is an array.'
+          end
+          hash = {}
+          hash[root.to_sym] = raw_fields.map(&:to_sym)
+          hash
+        else
+          {}
+        end
+      end
+
+    end
+  end
+end

lib/active_model_serializers.rb

@@ -1,6 +1,7 @@
 require "active_model"
 require "active_model/serializer/version"
 require "active_model/serializer"
+require "active_model/serializer/fieldset"
 
 begin
   require 'action_controller'

test/adapter/json_api/belongs_to_test.rb

@@ -45,6 +45,18 @@ def test_includes_linked_post
             assert_equal expected, @adapter.serializable_hash[:linked][:posts]
           end
 
+          def test_limiting_linked_post_fields
+            @adapter = ActiveModel::Serializer::Adapter::JsonApi.new(@serializer, include: 'post', fields: {post: [:title]})
+            expected = [{
+              title: 'New Post',
+              links: {
+                comments: ["1"],
+                author: "1"
+              }
+            }]
+            assert_equal expected, @adapter.serializable_hash[:linked][:posts]
+          end
+
           def test_include_nil_author
             serializer = PostSerializer.new(@anonymous_post)
             adapter = ActiveModel::Serializer::Adapter::JsonApi.new(serializer)

test/adapter/json_api/collection_test.rb

@@ -26,6 +26,15 @@ def test_include_multiple_posts
                            { title: "New Post", body: "Body", id: "2", links: { comments: [], author: "1" } }
                          ], @adapter.serializable_hash[:posts])
           end
+
+          def test_limiting_fields
+            @adapter = ActiveModel::Serializer::Adapter::JsonApi.new(@serializer, fields: ['title'])
+            assert_equal([
+              { title: "Hello!!", links: { comments: [], author: "1" } },
+              { title: "New Post", links: { comments: [], author: "1" } }
+            ], @adapter.serializable_hash[:posts])
+          end
+
         end
       end
     end

test/adapter/json_api/has_many_test.rb

@@ -32,7 +32,7 @@ def setup
           def test_includes_comment_ids
             assert_equal(["1", "2"], @adapter.serializable_hash[:posts][:links][:comments])
           end
-
+          
           def test_includes_linked_comments
             @adapter = ActiveModel::Serializer::Adapter::JsonApi.new(@serializer, include: 'comments')
             expected = [{
@@ -53,6 +53,24 @@ def test_includes_linked_comments
             assert_equal expected, @adapter.serializable_hash[:linked][:comments]
           end
 
+          def test_limit_fields_of_linked_comments
+            @adapter = ActiveModel::Serializer::Adapter::JsonApi.new(@serializer, include: 'comments', fields: {comment: [:id]})
+            expected = [{
+              id: "1",
+              links: {
+                post: "1",
+                author: nil
+              }
+            }, {
+              id: "2",
+              links: {
+                post: "1",
+                author: nil
+              }
+            }]
+            assert_equal expected, @adapter.serializable_hash[:linked][:comments]
+          end
+
           def test_no_include_linked_if_comments_is_empty
             serializer = PostSerializer.new(@post_without_comments)
             adapter = ActiveModel::Serializer::Adapter::JsonApi.new(serializer)

test/serializers/attributes_test.rb

@@ -12,7 +12,11 @@ def test_attributes_definition
         assert_equal([:name, :description],
                      @profile_serializer.class._attributes)
       end
+
+      def test_attributes_with_fields_option
+        assert_equal({name: 'Name 1'},
+                     @profile_serializer.attributes( { fields: [:name] } ) )
+      end
     end
   end
 end
-

test/serializers/fieldset_test.rb

@@ -0,0 +1,26 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class FieldsetTest < Minitest::Test
+
+      def test_fieldset_with_hash
+        fieldset = ActiveModel::Serializer::Fieldset.new({'post' => ['id', 'title'], 'coment' => ['body']})
+
+        assert_equal(
+          {:post=>[:id, :title], :coment=>[:body]}, 
+          fieldset.fields
+        )
+      end
+
+      def test_fieldset_with_array_of_fields_and_root_name
+        fieldset = ActiveModel::Serializer::Fieldset.new(['title'], 'post')
+
+        assert_equal(
+          {:post => [:title]}, 
+          fieldset.fields
+        )
+      end
+    end
+  end
+end