Fix loading factories in extensions after the last changes in Solidus

This commit reflects the last changes we made in Solidus to
support the new FactoryBot loading mechanism.

When testing extensions using Solidus vesions that support
the definition_file_paths, it will load the core factory first
and then the ones defined in
`lib/extension_name/testing_support/factories`.

lib/solidus_dev_support/testing_support/factories.rb

@@ -1,27 +1,51 @@
 # frozen_string_literal: true
 
-require 'spree/testing_support/factories'
+begin
+  require 'spree/testing_support/factory_bot'
+rescue LoadError
+  require 'spree/testing_support/factories'
+end
 require 'factory_bot'
 
 module SolidusDevSupport
   module TestingSupport
     module Factories
       def self.load_for(*engines)
         paths = engines.flat_map do |engine|
-          engine.root.glob('lib/**/factories.rb')
+          factories_file_or_folder = engine.root.glob('lib/*/testing_support/factories{,.rb}')
+
+          if factories_file_or_folder.size == 2 && using_factory_bot_deinition_file_paths?
+            folder, file = factories_file_or_folder.partition(&:directory?).map(&:first).map { |path| path.to_s.gsub(engine.root.to_s, '') }
+            ActiveSupport::Deprecation.warn <<-WARN.squish, caller(4)
+              SolidusDevSupport::TestingSupport::Factories.load_for() is automatically loading
+              all factories present into #{folder}. You should now safely remove #{file} if it
+              is only used to load ./factories content.
+            WARN
+
+            engine.root.glob('lib/*/testing_support/factories/**/*_factory.rb')
+          else
+            factories_file_or_folder
+          end.map { |path| path.sub(/.rb\z/, '').to_s }
         end
 
-        if Spree::TestingSupport.respond_to? :load_all_factories
-          FactoryBot.definition_file_paths.concat(
-            paths.map { |path| path.sub(/.rb\z/, '').to_s }
-          )
+        if using_factory_bot_deinition_file_paths?
+          FactoryBot.definition_file_paths = [
+            Spree::TestingSupport::FactoryBot.definition_file_paths,
+            paths,
+          ].flatten
+
           FactoryBot.reload
         else
           FactoryBot.find_definitions
 
           paths.each { |path| require path }
         end
       end
+
+      def self.using_factory_bot_deinition_file_paths?
+        defined?(Spree::TestingSupport::FactoryBot) &&
+          Spree::TestingSupport::FactoryBot.respond_to? :definition_file_paths
+      end
     end
   end
 end