Fixed duplicate root keys fixes #521

lib/active_model/serializable.rb

@@ -3,7 +3,9 @@ module Serializable
     def as_json(options={})
       if root = options.fetch(:root, json_key)
         hash = { root => serializable_object }
-        hash.merge!(serializable_data)
+
+        merge_hash(hash, serializable_data)
+
         hash
       else
         serializable_object
@@ -21,5 +23,15 @@ def serializable_data
     def embedded_in_root_associations
       {}
     end
+
+    def merge_hash(destination, source)
+      source.each_pair do |key, value|
+        if destination[key].is_a?(Array)
+          destination[key].concat(value)
+        else
+          destination[key] = value
+        end
+      end
+    end
   end
 end

lib/active_model/serializer.rb

@@ -150,7 +150,7 @@ def embedded_in_root_associations
         if included_associations.include? name
           if association.embed_in_root?
             association_serializer = build_serializer(association)
-            hash.merge! association_serializer.embedded_in_root_associations
+            merge_hash(hash, association_serializer.embedded_in_root_associations)
 
             serialized_data = association_serializer.serializable_object
             key = association.root_key

test/fixtures/poro.rb

@@ -35,6 +35,15 @@ def comments
 class Comment < Model
 end
 
+class Catalog < Model
+  def sub_catalogs
+    @attributes[:sub_catalogs] ||= [
+      Catalog.new(name: 'Catalog 1', :sub_catalogs => []),
+      Catalog.new(name: 'Catalog 2', :sub_catalogs => [])
+    ]
+  end
+end
+
 ###
 ## Serializers
 ###
@@ -62,3 +71,8 @@ class PostSerializer < ActiveModel::Serializer
 class CommentSerializer < ActiveModel::Serializer
   attributes :content
 end
+
+class CatalogSerializer < ActiveModel::Serializer
+  attributes :name
+  has_many :sub_catalogs, root: :catalogs, embed: :ids, embed_in_root: true #serializer: CatalogSerializer
+end

test/unit/active_model/array_serializer/root_test.rb

@@ -98,5 +98,22 @@ def test_root_as_argument_takes_precedence
         }, @rooted_serializer.as_json(root: :argument))
       end
     end
+
+    class DuplicateRootKeysTest < Minitest::Test
+      def setup
+        @catalog = Catalog.new({ name: 'Catalog root' })
+        @serializer = ArraySerializer.new([@catalog], root: :catalogs)
+      end
+
+      def test_duplicate_root_keys_using_as_json
+        assert_equal({
+          catalogs: [
+            { name: 'Catalog root', 'sub_catalog_ids' => @catalog.sub_catalogs.map(&:object_id) },
+            { name: 'Catalog 1', 'sub_catalog_ids' => [] },
+            { name: 'Catalog 2', 'sub_catalog_ids' => [] },
+          ]
+        }, @serializer.as_json)
+      end
+    end
   end
 end