woocommerce/plugins/woocommerce-blocks/docs/extensibility/extend-rest-api-new-endpoint.md

Adding an endpoint to ExtendRestAPI

This document is intended for contrubtors to WooCommerce Blocks plugin, if you feel like a new endpoint should be added, feel free to open an issue or a PR detailing why.

Extending GET endpoints in Store API.

ExtendRestAPI needs to expose each endpoint individually. If you want to expose a new endpoint, you have to follow these steps:

1. In ExtendRestApi class, add your endpoint IDENTIFIER to the $endpoints variable.

use Automattic\WooCommerce\Blocks\StoreApi\Schemas\BillingAddressSchema;

private $endpoints = [ /* other identifiers */, BillingAddressSchema::IDENTIFIER ];

This is to prevent accidentally exposing new endpoints.

2. Inside your endpoint schema class (for this example, inside BillingAddressSchema), in its get_properties method, add this call at the end of the returned array.

You can pass extra parameters to get_extended_schema and those would be passed to third party code.

self::EXTENDING_KEY    => $this->get_extended_schema( self::IDENTIFIER ),

EXTENDING_KEY value is extensions, we use a constant to make sure we don't have a typo.

3. Inside the same class, in get_item_response, add the below line. Like get_extended_schema, you can pass extra parameters here as well.

Make sure to only expose what's needed.

self::EXTENDING_KEY    => $this->get_extended_data( self::IDENTIFIER, $cart_item ),

That's it, your endpoint would now contain extensions in your endpoint, and you can consume it in the frontend.

Extending a new endpoint is usually half the work, you will need to receive this data in the frontend and pass it to any other extensibility point (Slot, Filter, Event).