woocommerce-blocks

Register an inner block by implementing the IntegrationInterface in PHP, defining a block.json with a woocommerce checkout step as parent, and calling registerCheckoutBlock from @woocommerce/blocks-checkout in JavaScript. Persist the value with extensionCartUpdate and a Store API update callback.

Inner blocks are React components registered inside a specific checkout step via block.json, suited for form fields. SlotFills use registerPlugin with scope woocommerce-checkout to inject content into predefined slots like ExperimentalOrderMeta, which is simpler for banners and notices.

Store API session data is not automatically copied to orders. You must hook woocommerce_checkout_order_created and transfer the session value to the order with $order->update_meta_data() and $order->save().

Client-side filters can modify display values and block checkout with error messages, but they can be bypassed. Always re-validate extension data server-side in the woocommerce_store_api_register_update_callback and throw a RouteException on invalid input.

The registerPlugin call must include scope set to the exact string woocommerce-checkout; omitting it or using the wrong scope silently prevents rendering. Also verify the SlotFill component is imported from @woocommerce/blocks-checkout.