Relationships with serializer option don't work

[marceloperini]

Summary

When define a serializer with has_many, has_one or belongs_to relationship with serializer option, it not being used the correct serializer class for relationship objects.

Steps to reproduce

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "rails"
  gem "sqlite3"
  gem "fast_jsonapi", github: "Netflix/fast_jsonapi"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.text :message
  end

  create_table :comments, force: true do |t|
    t.integer :post_id

    t.text :message
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

class CommentSerializer
  include FastJsonapi::ObjectSerializer

  attributes :message
end

class PostSerializer
  include FastJsonapi::ObjectSerializer

  has_many :comments, serializer: ::CommentSerializer

  attributes :message
end

class SerializerTest < Minitest::Test
  def setup
    @post = Post.create(message: 'test message')
    @comment = Comment.create(message: 'test message',
                              post_id: @post.id)
  end

  def test_post_serializer
    post_serializer = PostSerializer.new(@post).serializable_hash

    assert_equal post_serializer, {
      data: {
        id: @post.id.to_s,
        type: :post,
        attributes: {
          message: @post.message
        },
        relationships: {
          comments: {
            data: [
              {
                id: @comment.id.to_s,
                type: :comment,
                attributes: {
                  message: @comment.message
                }
              }
            ]
          }
        }
      }
    }
  end

  def test_comment_serializer
    comment_serializer = CommentSerializer.new(@comment).serializable_hash

    assert_equal comment_serializer, {
      data: {
        id: @comment.id.to_s,
        type: :comment,
        attributes: {
          message: @comment.message
        }
      }
    }
  end
end

Expected behavior

When defining a serializer class for relationships it is expected to use the correct class.

Actual behavior

F

Failure:
SerializerTest#test_post_serializer [fast_jsonapi_test.rb:68]:
--- expected
+++ actual
@@ -1 +1 @@
-{:data=>{:id=>"1", :type=>:post, :attributes=>{:message=>"test message"}, :relationships=>{:comments=>{:data=>[{:id=>"1", :type=>:comment}]}}}}
+{:data=>{:id=>"1", :type=>:post, :attributes=>{:message=>"test message"}, :relationships=>{:comments=>{:data=>[{:id=>"1", :type=>:comment, :attributes=>{:message=>"test message"}}]}}}}

rails test fast_jsonapi_test.rb:65

D, [2019-09-14T18:40:41.825060 #46314] DEBUG -- :    (0.4ms)  begin transaction
D, [2019-09-14T18:40:41.826513 #46314] DEBUG -- :   Post Create (0.8ms)  INSERT INTO "posts" ("message") VALUES (?)  [["message", "test message"]]
D, [2019-09-14T18:40:41.826874 #46314] DEBUG -- :    (0.1ms)  commit transaction
D, [2019-09-14T18:40:41.827544 #46314] DEBUG -- :    (0.1ms)  begin transaction
D, [2019-09-14T18:40:41.827886 #46314] DEBUG -- :   Comment Create (0.2ms)  INSERT INTO "comments" ("post_id", "message") VALUES (?, ?)  [["post_id", 2], ["message", "test message"]]
D, [2019-09-14T18:40:41.828076 #46314] DEBUG -- :    (0.0ms)  commit transaction
.

Finished in 0.028896s, 69.2128 runs/s, 69.2128 assertions/s.
2 runs, 2 assertions, 1 failures, 0 errors, 0 skips

System configuration

Ruby version: 2.6.3p62 (2019-04-16 revision 67580) [x86_64-linux] FastJson version: master

[SeanJManning]

@marceloperini

See the answer in this StackOverFlow post:

https://stackoverflow.com/questions/55782066/how-to-get-the-fast-jsonapi-to-return-the-attributes-of-the-relationships

[joeytheman]

The stackoverflow post shows that an included attribute should be rendered. Looking at the test result, the included attribute is not rendered.

I am experiencing the same issue on Rails 6.

[joeytheman]

In order for the custom serializer to take effect, you have to specify the include option when initializing the serializer. The documentation does not make that clear.

IE

This

 post_serializer = PostSerializer.new(@post).serializable_hash

needs to change to

post_serializer = PostSerializer.new(@post, include: [:comments]).serializable_hash

[benwalsh]

This usage is tricky -- you have to pass custom options every time, instead of the attributes being consistent and defined in the Serializer itself. I was expecting to have something like:

class ProductSerializer
  include FastJsonapi::ObjectSerializer

  included :components, serializer: ProductComponentSerializer

or even

  has_many :components, include: { serializer: ProductComponentSerializer }

[marceloperini]

Thanks for the clarifications, it help me a lot. But I think this has to be more clear on the documentation