Serialize embedding in root deeply nested associations

Closes #444

lib/active_model/serializer.rb

@@ -149,15 +149,28 @@ end
       associations.each_with_object({}) do |(name, association), hash|
         if included_associations.include? name
           if association.embed_in_root?
-            hash[association.root_key] = serialize association
+            association_serializer = build_serializer(association)
+            hash.merge! association_serializer.embedded_in_root_associations
+
+            serialized_data = association_serializer.serializable_object
+            key = association.root_key
+            if hash.has_key?(key)
+              hash[key].concat(serialized_data).uniq!
+            else
+              hash[key] = serialized_data
+            end
           end
         end
       end
     end
 
-    def serialize(association)
+    def build_serializer(association)
       object = send(association.name)
-      association.build_serializer(object, scope: scope).serializable_object
+      association.build_serializer(object, scope: scope)
+    end
+
+    def serialize(association)
+      build_serializer(association).serializable_object
     end
 
     def serialize_ids(association)

test/fixtures/active_record.rb

@@ -80,13 +80,13 @@ ARPost.create(title: 'New post',
 
   short_tag = post.ar_tags.create(name: 'short')
   whiny_tag = post.ar_tags.create(name: 'whiny')
-  happy_tag = post.ar_tags.create(name: 'happy')
+  happy_tag = ARTag.create(name: 'happy')
 
   post.ar_comments.create(body: 'what a dumb post').tap do |comment|
-    comment.ar_tags.concat short_tag, whiny_tag
+    comment.ar_tags.concat happy_tag, whiny_tag
   end
 
   post.ar_comments.create(body: 'i liked it').tap do |comment|
-    comment.ar_tags.concat short_tag, happy_tag
+    comment.ar_tags.concat happy_tag, short_tag
   end
 end

test/integration/active_record/active_record_test.rb

@@ -14,9 +14,9 @@ module ActiveModel
         assert_equal({
           'ar_post' => {
             title: 'New post', body: 'A body!!!',
-            ar_comments: [{ body: 'what a dumb post', ar_tags: [{ name: 'short' }, { name: 'whiny' }] },
-                          { body: 'i liked it', ar_tags: [{:name=>"short"}, {:name=>"happy"}] }],
-            ar_tags: [{ name: 'short' }, { name: 'whiny' }, { name: 'happy' }],
+            ar_comments: [{ body: 'what a dumb post', ar_tags: [{ name: 'happy' }, { name: 'whiny' }] },
+                          { body: 'i liked it', ar_tags: [{:name=>"happy"}, {:name=>"short"}] }],
+            ar_tags: [{ name: 'short' }, { name: 'whiny' }],
             ar_section: { 'name' => 'ruby' }
           }
         }, post_serializer.as_json)
@@ -30,7 +30,7 @@ module ActiveModel
             'ar_post' => {
               title: 'New post', body: 'A body!!!',
               'ar_comment_ids' => [1, 2],
-              'ar_tag_ids' => [1, 2, 3],
+              'ar_tag_ids' => [1, 2],
               'ar_section_id' => 1
             }
           }, post_serializer.as_json)
@@ -41,18 +41,20 @@ module ActiveModel
         post_serializer = ARPostSerializer.new(@post)
 
         embed(ARPostSerializer, embed: :ids, embed_in_root: true) do
-          assert_equal({
-            'ar_post' => {
-              title: 'New post', body: 'A body!!!',
-              'ar_comment_ids' => [1, 2],
-              'ar_tag_ids' => [1, 2, 3],
-              'ar_section_id' => 1
-            },
-            ar_comments: [{ body: 'what a dumb post', ar_tags: [{ name: 'short' }, { name: 'whiny' }] },
-                          { body: 'i liked it', ar_tags: [{:name=>"short"}, {:name=>"happy"}] }],
-            ar_tags: [{ name: 'short' }, { name: 'whiny' }, { name: 'happy' }],
-            'ar_sections' => [{ 'name' => 'ruby' }]
-          }, post_serializer.as_json)
+          embed(ARCommentSerializer, embed: :ids, embed_in_root: true) do
+            assert_equal({
+              'ar_post' => {
+                title: 'New post', body: 'A body!!!',
+                'ar_comment_ids' => [1, 2],
+                'ar_tag_ids' => [1, 2],
+                'ar_section_id' => 1
+              },
+              ar_comments: [{ body: 'what a dumb post', 'ar_tag_ids' => [3, 2] },
+                            { body: 'i liked it', 'ar_tag_ids' => [3, 1] }],
+              ar_tags: [{ name: 'happy' }, { name: 'whiny' }, { name: 'short' }],
+              'ar_sections' => [{ 'name' => 'ruby' }]
+            }, post_serializer.as_json)
+          end
         end
       end
 

test/unit/active_model/serializer/has_many_test.rb

@@ -130,7 +130,7 @@ module ActiveModel
         @association.embed_in_root = true
         @association.serializer_class = Class.new(ActiveModel::Serializer) do
           def content
-            'fake'
+            object.read_attribute_for_serialization(:content) + '!'
           end
 
           attributes :content
@@ -138,7 +138,7 @@ module ActiveModel
 
         assert_equal({
           'post' => { title: 'Title 1', body: 'Body 1', 'comment_ids' => @post.comments.map { |c| c.object_id } },
-          comments: [{ content: 'fake' }, { content: 'fake' }]
+          comments: [{ content: 'C1!' }, { content: 'C2!' }]
         }, @post_serializer.as_json)
       end