Preforms a Double Nested includes to save us from N+1 queries. Used the bullet gem (https://github.com/flyerhzm/bullet) to fine tune this => thanks @flyerhzm

double_nested_spree.rb

# //////////////////////////////////////////////////////
#
# spree_wizard, https://github.com/think602/spree_wizard
#
# //////////////////////////////////////////////////////



# ================================================
# Controller code preforming Rails SQL lookup
# ------------------------------------------------
module Spree
  class WizardsController < Spree::StoreController

    # Get taxon and eager load associated objects
    # GET /wizards/taxon/1/products.json
    def taxon_products
      @taxon = Spree::Taxon.
        includes(products: { variants: [:images, :default_price, :option_values]}).
        includes(products: { master:   [:images, :default_price, :option_values]}).
        find(params[:taxon_id])
      
      render 'spree/wizards/taxon_products_api', formats: :json, object: @taxon
    end
    
  end
end


# ================================================
# RABL JSON rendering code
# ------------------------------------------------

object @taxon

child :products do 
  attributes :id, :name, :price, :description, :sku, :taxon_ids
  
  node(:attachment_url) { |p| p.images.try(:first).try(:attachment).try(:url) } 
  node(:announcement )  { false }
  
  child :variants do 
    attributes :id, :price, :is_master
    
    child :option_values do 
      attributes :name
    end
  end
  
end