> ## Documentation Index
> Fetch the complete documentation index at: https://spreecommerce-documentation-update-4-5-to-4-6.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Updating Extensions

> How to upgrade your Spree extension to work with Spree 4

## Zeitwerk compatibility

Zeitwerk is the [new default code autoloader in Rails 6](https://weblog.rubyonrails.org/2019/2/22/zeitwerk-integration-in-rails-6-beta-2/).

This doesn't work well with the old approach to decorators (files that name ends with decorator.rb, eg. `app/models/spree/order_decorator.rb`) using [class\_eval](https://www.jimmycuadra.com/posts/metaprogramming-ruby-class-eval-and-instance-eval/).

To fix this we need to convert all `class_eval` decorators to modules and use [Module.prepend](https://medium.com/@leo_hetsch/ruby-modules-include-vs-prepend-vs-extend-f09837a5b073). Also we need to name them properly according to [Zeitwerk naming rules](https://github.com/fxn/zeitwerk#file-structure)

Example of an old decorator:

`app/models/spree/order_decorator.rb`

```ruby
Spree::Order.class_eval do
  has_many :new_custom_model

  def some_method
     # ...
  end
end
```

the same decorator in the new notation:

`app/models/your_extension_name/order_decorator.rb`

```ruby
module YourExtensionName::OrderDecorator
  def self.prepended(base)
    base.has_many :new_custom_model
  end

  def some_method
    # ...
  end
end

Spree::Order.prepend(YourExtensionName::OrderDecorator)
```

## Fixing Deface Overrides

Please remember to prepare versioned overrides for both Spree 3.x and 4.x, eg. [https://github.com/spree-contrib/spree\_static\_content/commit/e4b9e4900024235158d0ec1a48a100b4732348ef](https://github.com/spree-contrib/spree_static_content/commit/e4b9e4900024235158d0ec1a48a100b4732348ef)

Spree 4 uses Bootstrap 4 and many partials and HTML structure changed compared to Spree 3.x.

Also - **remember to add deface gem to gemspec** as deface itself was removed as a dependency of Spree. eg. [https://github.com/spree/spree\_auth\_devise/commit/d729689ca87d8586e541ffcc865ef1e0a5a79fe4](https://github.com/spree/spree_auth_devise/commit/d729689ca87d8586e541ffcc865ef1e0a5a79fe4)

## Migrate to Spree Dev Tools

Replace all development dependencies with:

```ruby
s.add_development_dependency 'spree_dev_tools'
```

Replace `spec_helper.rb` contents with:

[https://github.com/spree/spree/blob/777a284b4c70e69d32a05ffa61bbe3905d8f1297/cmd/lib/spree\_cmd/templates/extension/spec/spec\_helper.rb](https://github.com/spree/spree/blob/777a284b4c70e69d32a05ffa61bbe3905d8f1297/cmd/lib/spree_cmd/templates/extension/spec/spec_helper.rb)

Example migrations:

* [https://github.com/spree/spree\_gateway/pull/357](https://github.com/spree/spree_gateway/pull/357)
* [https://github.com/spree-contrib/spree-product-assembly/pull/200](https://github.com/spree-contrib/spree-product-assembly/pull/200)
* [https://github.com/spree/spree\_auth\_devise/pull/487](https://github.com/spree/spree_auth_devise/pull/487)