Allow to set root for associations through options

lib/active_model/serializer/associations.rb

@@ -14,7 +14,7 @@ module ActiveModel
         self.serializer_class = @options[:serializer]
       end
 
-      attr_reader :name, :embed_ids, :embed_objects, :embed_key, :serializer_class
+      attr_reader :name, :embed_ids, :embed_objects, :embed_key, :serializer_class, :options
       attr_accessor :include
       alias embed_ids? embed_ids
       alias embed_objects? embed_objects
@@ -49,7 +49,7 @@ module ActiveModel
         end
 
         def embedded_key
-          name.pluralize
+          @options[:root] || name.pluralize
         end
       end
 
@@ -59,7 +59,7 @@ module ActiveModel
         end
 
         def embedded_key
-          name
+          @options[:root] || name
         end
       end
     end

test/unit/active_model/serializer/has_many_test.rb

@@ -9,6 +9,7 @@ module ActiveModel
         @association = PostSerializer._associations[0]
         @association.include = false
         @association.embed = :ids
+        @association.options[:root] = nil
       end
 
       def test_associations_definition
@@ -43,6 +44,14 @@ module ActiveModel
         }, @post_serializer.as_json)
       end
 
+      def test_associations_embedding_objects_serialization_using_serializable_hash_and_root_from_options
+        @association.embed = :objects
+        @association.options[:root] = 'root'
+        assert_equal({
+          'title' => 'Title 1', 'body' => 'Body 1', 'root' => [{ 'content' => 'C1' }, { 'content' => 'C2' }]
+        }, @post_serializer.serializable_hash)
+      end
+
       def test_associations_embedding_ids_including_objects_serialization_using_serializable_hash
        @association.include = true
         assert_equal({

test/unit/active_model/serializer/has_one_test.rb

@@ -9,6 +9,7 @@ module ActiveModel
         @association = UserSerializer._associations[0]
         @association.include = false
         @association.embed = :ids
+        @association.options[:root] = nil
       end
 
       def test_associations_definition
@@ -43,6 +44,14 @@ module ActiveModel
         }, @user_serializer.as_json)
       end
 
+      def test_associations_embedding_objects_serialization_using_serializable_hash_and_root_from_options
+        @association.embed = :objects
+        @association.options[:root] = 'root'
+        assert_equal({
+          'name' => 'Name 1', 'email' => 'mail@server.com', 'root' => [{ 'name' => 'N1', 'description' => 'D1' }]
+        }, @user_serializer.serializable_hash)
+      end
+
       def test_associations_embedding_ids_including_objects_serialization_using_serializable_hash
         @association.include = true
         assert_equal({