title: Rails 4 - Pundit::PolicyScopingNotPerformedError
body: <p>I am new with Pundit ( I am used to Cancan...)  and I am training on it, trying to follow the ReadMe.. but I am stuck with the PolicyScoping error when indexing all sheets from my Sheet model </p>
  
  <pre><code>#application_controller.rb
  class ApplicationController &lt; ActionController::Base
      include Pu ndit 
      .../... 
  end  
  
  #sheets_controller.rb
  class SheetsController &lt; ApplicationController
      after_filter :verify_authorized, :except =&gt; :index, unless: :devise_controller?
      after_filter :verify_policy_scoped, :only =&gt; :index
  
      before_action :set_sheet, only: [:show, :edit, :update, :destroy]
      respond_to :html, :json
  
      def index 
        @sheets = SheetPolicy::Scope.new(current_user, Sheet).resolve
        build_json_header_list
        respond_to do |format|
          format.html
          format.json { 
            build_json_data_list
            render json: @data 
          }
        end
      end
      .../... 
  end
  
  #sheet_policy.rb
  class SheetPolicy &lt; ApplicationPolicy
    .../... 
    class Scope &lt; Scope
      def resolve
        byebug
        if user.system_admin?
          scope.all
        else
          scope.where(:user_id =&gt; user.id)
        end
      end
    end
  end
  </code></pre>
  
  <p>The index methods ais correctly executed , the sheet_policy scope is correctly resolved ( debugged in console ... and the view start rendering ... so I guess the error comes from the after_filer in the sheets_controller</p>
  
  <pre><code>    after_filter :verify_policy_scoped, :only =&gt; :index
  </code></pre>
  
  <p>BUT I thought ( I must e wrong...) that resolving the scope wit  the sheet policy SHOUDL have authorised the index action ?the Pundit doc is not very clear on it ...</p>
  
  <p>here is the console log </p>
  
  <pre><code>=====================
  # development.log
  Started GET "/sheets" for ::1 at 2015-09-18 11:59:30 +0200
  Processing by SheetsController#index as HTML
    User Load (0.5ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1  ORDER BY "users"."id" ASC LIMIT 1  [["id", 1]]
  
  [18, 27] in .../app/policies/sheet_policy.rb
  (byebug) user.system_admin?
    Role Load (22.9ms)  SELECT "roles".* FROM "roles"
  true
  (byebug) c
    CACHE (0.3ms)  SELECT "roles".* FROM "roles"
    Rendered sheets/index.html.erb within layouts/administration (17.0ms)
    .../...
    Rendered layouts/administration/_scripts.html.erb (286.9ms)
    Completed 500 Internal Server Error in 29650ms (Views: 6149.5ms | ActiveRecord: 25.3ms)
  ------
  
    Pundit::PolicyScopingNotPerformedError - Pundit::PolicyScopingNotPerformedError:
      pundit (1.0.1) lib/pundit.rb:107:in `verify_policy_scoped'  activesupport (4.2.3)  
      lib/active_support/callbacks.rb:430:in `block in make_lambda'
      .../...
      activesupport (4.2.3) lib/active_support/callbacks.rb:88:in `run_callbacks'
      actionpack (4.2.3) lib/abstract_controller/callbacks.rb:19:in `process_action'
      .../...
      activesupport (4.2.3) lib/active_support/notifications.rb:164:in `block in instrument'
      .../...
      actionpack (4.2.3) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
      .../...
      activerecord (4.2.3) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  </code></pre>