Don't memoize association serializer

test/unit/active_model/array_serializer/serialization_test.rb

@@ -78,6 +78,36 @@ module ActiveModel
       ensure
         PostSerializer._associations[:comments] = @old_association
       end
+
+      def test_embed_object_for_has_one_association_with_nil_value
+        @association = UserSerializer._associations[:profile]
+        @old_association = @association.dup
+
+        @association.embed = :objects
+
+        @user1 = User.new({ name: 'User 1', email: 'email1@server.com' })
+        @user2 = User.new({ name: 'User 2', email: 'email2@server.com' })
+
+        class << @user1
+          def profile
+            nil
+          end
+        end
+
+        class << @user2
+          def profile
+            @profile ||= Profile.new(name: 'Name 1', description: 'Desc 1')
+          end
+        end
+
+        @serializer = ArraySerializer.new([@user1, @user2]) #, root: :posts)
+        assert_equal([
+          { name: "User 1", email: "email1@server.com", profile: nil },
+          { name: "User 2", email: "email2@server.com", profile: { name: 'Name 1', description: 'Desc 1' } }
+        ], @serializer.as_json)
+      ensure
+        UserSerializer._associations[:profile] = @old_association
+      end
     end
   end
 end

test/unit/active_model/serializer/has_many_test.rb

@@ -128,7 +128,7 @@ module ActiveModel
       def test_associations_using_a_given_serializer
         @association.embed = :ids
         @association.embed_in_root = true
-        @association.serializer_class = Class.new(ActiveModel::Serializer) do
+        @association.serializer_from_options = Class.new(ActiveModel::Serializer) do
           def content
             object.read_attribute_for_serialization(:content) + '!'
           end
@@ -145,7 +145,7 @@ module ActiveModel
       def test_associations_embedding_ids_using_a_given_array_serializer
         @association.embed = :ids
         @association.embed_in_root = true
-        @association.serializer_class = Class.new(ActiveModel::ArraySerializer) do
+        @association.serializer_from_options = Class.new(ActiveModel::ArraySerializer) do
           def serializable_object
             { my_content: ['fake'] }
           end
@@ -158,7 +158,7 @@ module ActiveModel
       end
 
       def test_associations_embedding_objects_using_a_given_array_serializer
-        @association.serializer_class = Class.new(ActiveModel::ArraySerializer) do
+        @association.serializer_from_options = Class.new(ActiveModel::ArraySerializer) do
           def serializable_object
             { my_content: ['fake'] }
           end

test/unit/active_model/serializer/has_one_test.rb

@@ -119,7 +119,7 @@ module ActiveModel
       def test_associations_embedding_ids_using_a_given_serializer
         @association.embed = :ids
         @association.embed_in_root = true
-        @association.serializer_class = Class.new(ActiveModel::Serializer) do
+        @association.serializer_from_options = Class.new(ActiveModel::Serializer) do
           def name
             'fake'
           end
@@ -134,7 +134,7 @@ module ActiveModel
       end
 
       def test_associations_embedding_objects_using_a_given_serializer
-        @association.serializer_class = Class.new(ActiveModel::Serializer) do
+        @association.serializer_from_options = Class.new(ActiveModel::Serializer) do
           def name
             'fake'
           end

test/unit/active_model/serializer/scope_test.rb

@@ -31,7 +31,7 @@ module ActiveModel
       end
 
       def test_scope_passed_through
-        @association.serializer_class = Class.new(ActiveModel::Serializer) do
+        @association.serializer_from_options = Class.new(ActiveModel::Serializer) do
           def name
             scope
           end