Checkout Blocks implementation notes for notice extensions

Blocks require an explicit integration

WooCommerce documents Cart and Checkout Blocks as extensible JavaScript applications. Extensions should use supported integration interfaces, declare compatibility after testing and avoid assuming that legacy shortcode hooks are migrated. The exact insertion point must be stable across hydration and cart updates.

Build and dependency discipline

Register scripts with the generated dependency asset and WooCommerce’s shared packages rather than bundling duplicate framework code. Keep the shopper bundle narrow: the notice component needs presentation and language configuration, not customer or order state.

Treat missing block globals or registration errors as a controlled no-output state with an administrator diagnostic. Do not inject markup by polling the DOM or depending on undocumented class names.

Test the checkout lifecycle

Verify initial render, server hydration, address validation, shipping recalculation, payment-method switching and error recovery. Inspect the browser console and network log. The notice should not create external requests, change totals or become the source of a failed checkout.

Document the WooCommerce versions tested and repeat the matrix against the minimum and current stable versions before declaring compatibility.

Separate evidence from a compatibility declaration

WooCommerce treats compatibility declarations as useful signals, not substitutes for testing. A credible review records the WooCommerce version, active theme, block markup, guest state, browser, viewport and the exact extension build. It also records absence: no console exception, no failed first-party request, no duplicated notice and no change to totals or checkout submission.

Notice27 1.2 has both a declared Cart/Checkout Blocks path and final local runtime evidence. The evidence set covers real Cart Block and Checkout Block pages at desktop, tablet and mobile sizes. That supports the narrow stable claim on the public compatibility page; it does not prove every theme, checkout extension, cache layer or future WooCommerce release.

Include a deliberate failure check. Disable or misregister the integration in staging and confirm the administrator can diagnose the missing output without exposing a warning to shoppers or breaking checkout. Then restore the supported build and verify the notice returns once. This tests operational recovery, not only the happy path.

Keep screenshots tied to the exact build and route. A cropped notice alone does not prove that the order button, validation summary and responsive layout remained usable. The strongest record pairs a full-page capture with a focused image, console result, viewport dimensions and the tested plugin checksum.

Retest both an empty and populated cart. Blocks render different structures as state changes, and extensions may re-run filters after quantity, shipping or payment updates. Confirm one notice remains in the approved position after each state change and that removing the last item does not leave orphaned output or an inaccessible empty-cart view.

Keep the evidence reproducible by recording seed products and checkout settings. A screenshot made from an unknown cart state is difficult to compare after an update, while a deterministic fixture makes visual, accessibility and request failures easier to isolate.

• Declare compatibility only for versions and paths actually exercised.
• Retest after WooCommerce, theme or checkout-extension changes.
• Keep the shopper path local and independent of licence-server availability.
• Treat a clean classic checkout as separate from Block evidence.