Don't try to add jsonapi_serialize as helper unless it's possible to do so

[mecampbellsoup]

Description

From: heartcombo/devise#3732

Currently Devise::Controllers::Helpers depends on #helper_method, which is defined inside AbstractController::Helpers. This module is included in ActionController::Base, but it is not included by default in ActionController::Metal.

helper_method is not essential to the functionality of the methods inside Devise::Controllers::Helpers, so this PR wraps all Devise #helper_method calls with respond_to?(:helper_method) checks.

This console output elucidates the issue:

[14] pry(main)> ActionController::Base.ancestors.map(&:to_s).grep(/Helpers/)
=> ["ActionDispatch::Routing::RouteSet::MountedHelpers", "ActionController::Helpers", "AbstractController::Helpers"]
[15] pry(main)> ApplicationController.ancestors.map(&:to_s).grep(/Helpers/)
=> ["ActionDispatch::Routing::RouteSet::MountedHelpers"]

Background

• Rails 5.0.0.rc1
• RAILS_ENV=test (was trying to run a new API's first request specs)

[mecampbellsoup]

@tiagopog updated with description

[tiagopog]

Good one, @mecampbellsoup 👍