Fixes isse when zeitwerk is not enabled

If autoloaders is defined in the Rails object, but the
autoloader zeitwerk is not used, it is defined but returns
nil when calling `main`, this ensures the extra check.

Gemfile

@@ -8,7 +8,7 @@ gem 'solidus_core', github: 'solidusio/solidus', branch: branch
 # Specify your gem's dependencies in solidus_support.gemspec
 gemspec
 
-gem 'solidus_extension_dev_tools', github: 'solidusio-contrib/solidus_extension_dev_tools'
+gem 'solidus_dev_support', github: 'solidusio-contrib/solidus_dev_support'
 gem 'sprockets', '~> 3'
 gem 'sprockets-rails'
 

lib/solidus_support/engine_extensions/decorators.rb

@@ -14,7 +14,7 @@ module ClassMethods
         def activate
           base_path = root.join('app/decorators')
 
-          if Rails.respond_to?(:autoloaders)
+          if Rails.respond_to?(:autoloaders) && Rails.autoloaders.main
             # Add decorators folder to the Rails autoloader. This
             # allows Zeitwerk to resolve decorators paths correctly,
             # when used.

solidus_support.gemspec

@@ -22,5 +22,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rubocop'
   spec.add_development_dependency 'rubocop-rspec'
   spec.add_development_dependency 'solidus_core'
-  spec.add_development_dependency 'solidus_extension_dev_tools'
+  spec.add_development_dependency 'solidus_dev_support'
 end

spec/spec_helper.rb

@@ -1,4 +1,4 @@
 # frozen_string_literal: true
 
 require_relative 'support/dummy_app'
-require 'solidus_extension_dev_tools/rspec/spec_helper'
+require 'solidus_dev_support/rspec/spec_helper'