jsonapi-rails breaks the shortcut form of ActionController#render

[smaximov]

jsonapi-rails breaks the shortcut form of render which dispatches on the single argument's value (render :action_name, render 'template/name', render '/file/name').

I have stumbled upon this issue when tried out the 'ActiveRecord Errors' branch.

This can be reproduced on the current HEADs of both master (dc373eb) and ar-validation-errors (498c2b5).

Steps to reproduce

1. (Optional) Create new gemset to ensure clean environment:

rvm use 2.3.3@jsonapi --create

2. Create and configure new Rails 4.2 application:

gem install rails:4.2 bundler
rails new jsonapi-test --skip-bundle --skip-sprockets --skip-spring --skip-javascript --skip-turbolinks --skip-test-unit
cd jsonapi-test
cat <<RUBY > Gemfile
source 'https://rubygems.org'
gem 'rails', '4.2'
gem 'sqlite3'
gem 'jsonapi-rails', github: 'jsonapi-rb/jsonapi-rails', ref: 'dc373eb'
RUBY
bundle install

3. Setup sample resource

bin/rails generate model Post title:text
echo '2.times { |i| Post.create!(title: "Post ##{i + 1}") }' > db/seeds.rb
bin/rake db:create db:migrate db:seed
bin/rails generate jsonapi:serializable Post

4. Setup sample actions

cat <<RUBY > config/routes.rb
Rails.application.routes.draw do
  get '/api', to: 'application#api'
  get '/html', to: 'application#html'
end
RUBY
cat <<RUBY > app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  # sample action to make sure jsonapi-rails works
  def api
    render jsonapi: Post.all
  end

  # this action fails
  def html
    render :welcome
  end
end
RUBY

5. Start Rails server and hit '/api' to make sure jsonapi-rails works.

6. Hit '/html'

Expected behavior

Rails fails with an ActionView::MissingTemplate error.

Actual behavior

Rails fails with the following error:

NoMethodError (undefined method `merge' for :welcome:Symbol)
  app/controllers/application_controller.rb:9:in `html'

[... backtrace ...]

Workarounds

Some debugging reveals that the error comes from this line (introduced in 20a6756) where #merge is being called on the :welcome Symbol.

I'm not very familiar with the Rails internals, but it seems like the signature of JSONAPI::Rails::ActionController#render (which takes a single hash argument) is not compatible with the ActionPack's render (both AbstractController::Rendering and ActionController::Renderer can take variable number of arguments).

I see several workarounds:

1. Change the signature of JSONAPI::Rails::ActionController#render and have it normalize its arguments somehow. But this will likely duplicate the work ActionPack does under the hood to process the shortcut syntax of render.

2. Drop JSONAPI::Rails::ActionController#render and override AbstractController::Rendering#_normalize_options instead. I don't like it because _normalize_options is kinda undocumented and I have not seen a project that actually uses it.

3. Move providing :_reverse_mapping inside the renderer proc, since the proc is evaluated in the controller context and has access to request. Another benefit is that it will modify options passed to the JSONAPI renderers only.

I have implemented the second and the third options and they both work on the sample application.

[beauby]

Thanks a lot for the thorough investigation and explanation! Got my laptop stolen tonight so I'll try to review and merge tomorrow.