Blacklight helper behaviors overridden by app not available to Spotlight engine

[rwd]

Blacklight's strategy for allowing helpers to be overriden by an app, by using behavior modules, does not work with Spotlight.

For example, given a helper in the app containing:

module UrlHelper
  include Blacklight::UrlHelperBehavior

  def url_for_document(doc, options = {})
    '/special/path'
  end
end

Blacklight will use the app's overriden helper method, but Spotlight will not.

I expect that this is due to the Rails engine having isolated namespace and so being unaware of overrides in the app.

[cbeer]

I think we got around that for some other helpers by whitelisting the relevant application helpers:

   def main_app_url_helper?(method)
      (method.to_s.end_with?('_path') || method.to_s.end_with?('_url')) &&
        main_app.respond_to?(method)
    end

https://github.com/sul-dlss/spotlight/blob/master/app/helpers/spotlight/application_helper.rb#L156-159

I wonder if we should add that to the particular route to the whitelist, and hope there aren't too many similar ones (or, build out some engine configuration so application's can push the relevant overrides to Spotlight)?

Another couple workarounds I can think of are::

• push url_for_document into a Blacklight::DocumentPresenter
• change the application's config/routes.rb file to do the appropriate routing.
• use blacklight_config.show.route [1] instead of overriding the helper
• use Rails' polymorphic routing and implement #to_model or other appropriate Rails model routing methods

@jcoyne @jkeck @mejackreed ?

[1] https://github.com/projectblacklight/blacklight/blob/master/app/helpers/blacklight/url_helper_behavior.rb#L13-18

[rwd]

I don't think that the whitelist in Spotlight::ApplicationHelper#main_app_url_helper? will help here because the method is not missing; it is provided by Blacklight and so #main_app_url_helper? never gets called for it.