woocommerce/plugins/woocommerce-blocks/docs/internal-developers/blocks/feature-flags-and-experimental-interfaces.md

# Features Flags and Experimental Interfaces <!-- omit in toc -->

## Table of contents <!-- omit in toc -->

-   [Blocks behind flags](#blocks-behind-flags)
    -   [Feature plugin flag](#feature-plugin-flag)
    -   [Experimental flag](#experimental-flag)
-   [Features behind flags](#features-behind-flags)
    -   [Feature plugin flag](#feature-plugin-flag-1)
    -   [Experimental plugin flag](#experimental-plugin-flag)
-   [Processes and commands that use a flag](#processes-and-commands-that-use-a-flag)
-   [Usages of `__experimental` prefix](#usages-of-__experimental-prefix)
    -   [PHP filters and actions](#php-filters-and-actions)
    -   [JS methods](#js-methods)
    -   [Slots](#slots)
    -   [Misc](#misc)
-   [Usages of `experimental` prefix](#usages-of-experimental-prefix)

We have feature gating system setup in our plugin that defines what is accessible to the public and what is not, it has three phases:

-   **Core flag `WOOCOMMERCE_BLOCKS_PHASE=1`:** anything that is not hidden behind a flag, falls under this category, and it contains all of the code that runs on WooCommerce Core plugin.
-   **Feature plugin flag `WOOCOMMERCE_BLOCKS_PHASE=2`**: anything that is behind this flag is code that is shipped to our [feature plugin](https://wordpress.org/plugins/woo-gutenberg-products-block/), the files of blocks behind this flag are also present in WooCommerce Core, just not active.
-   **Experimental flag `WOOCOMMERCE_BLOCKS_PHASE=3`**: This flag contains things that we're not shipping yet, so unfinished work mostly. These features are only available in developer builds of the plugin.

We also use an `__experimental` prefix for any experimental interfaces. This is a signal to those reading our code that it should not be implemented in for production use. Currently this prefix is used in the following ways:

-   Prefixing references that are experimental. An example would be PHP action or filter slugs.
-   Prefixing functions or methods that are experimental.

## Blocks behind flags

The majority of our feature flagging is blocks, this is a list of them:

### Feature plugin flag

### Experimental flag

-   Single Product block ([PHP flag](https://github.com/woocommerce/woocommerce-blocks/blob/cb11cd2537e35561a9c930f893ee72d82ab6bc75/src/BlockTypesController.php#L227) | [webpack flag](https://github.com/woocommerce/woocommerce-blocks/blob/cb11cd2537e35561a9c930f893ee72d82ab6bc75/bin/webpack-entries.js#L68)).
-   ⚛️ Add to cart ([JS flag](https://github.com/woocommerce/woocommerce-blocks/blob/dfd2902bd8a247b5d048577db6753c5e901fc60f/assets/js/atomic/blocks/product-elements/add-to-cart/index.ts#L26-L29)).

## Features behind flags

We also have individual features or code blocks behind a feature flag, this is a list of them:

### Feature plugin flag

-   ⚛️ Product Price new controls ([JS flag](https://github.com/woocommerce/woocommerce-blocks/blob/74badf254ecfe0c7811713a0f847a87f139c69c3/assets/js/atomic/blocks/product-elements/price/supports.ts#L14-L37)).
-   ⚛️ Product Title new controls ([JS flag 1](https://github.com/woocommerce/woocommerce-blocks/blob/fd8eeb7f49f0454d746d581bc892cf3c2d9e30cc/assets/js/atomic/blocks/product-elements/title/attributes.ts#L25-L32) | [JS flag 2-1](https://github.com/woocommerce/woocommerce-blocks/blob/df6d820bb47459d56c1329729ab8c364a1b8fddc/assets/js/atomic/blocks/product-elements/title/block.tsx#L84) | [JS flag 2-2](https://github.com/woocommerce/woocommerce-blocks/blob/df6d820bb47459d56c1329729ab8c364a1b8fddc/assets/js/atomic/blocks/product-elements/title/block.tsx#L88) | [JS flag 2-3](https://github.com/woocommerce/woocommerce-blocks/blob/df6d820bb47459d56c1329729ab8c364a1b8fddc/assets/js/atomic/blocks/product-elements/title/block.tsx#L110) | [JS flag 2-4](https://github.com/woocommerce/woocommerce-blocks/blob/df6d820bb47459d56c1329729ab8c364a1b8fddc/assets/js/atomic/blocks/product-elements/title/block.tsx#L114) | [JS flag 3-1](https://github.com/woocommerce/woocommerce-blocks/blob/c734f3e846b8da7d49a03347d92354efd786251f/assets/js/atomic/blocks/product-elements/title/edit.tsx#L45-L52) | [JS flag 3-2](https://github.com/woocommerce/woocommerce-blocks/blob/c734f3e846b8da7d49a03347d92354efd786251f/assets/js/atomic/blocks/product-elements/title/edit.tsx#L98)).

## Processes and commands that use a flag

-   `npm run build:deploy` uses the feature plugin flag ([env flag](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/c0de18ec0a798c072420c67a689e4cc4d3ac77c9/package.json#L28)).
-   GitHub actions uses the experimental flag when running automated tests ([env flags 1](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/4cedb65367be0d1c4c1f9dd9c016e3b1325cf92e/.github/workflows/php-js-e2e-tests.yml) | [env flags 2](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/4cedb65367be0d1c4c1f9dd9c016e3b1325cf92e/.github/workflows/unit-tests.yml)).
-   webpack creates a `blocks.ini` when running ([env flag](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/961c0c476d4228a218859c658c42f9b6eebfdec4/bin/webpack-configs.js#L110-L119)).
-   webpack filters out experimental blocks when building. ([env flag](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/b3a9753d8b7dae18b36025d09fbff835b8365de0/bin/webpack-entries.js#L61-L66)).
-   certain E2E tests are skipped if the environment is not met ([env flag 1](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/961c0c476d4228a218859c658c42f9b6eebfdec4/tests/e2e/specs/backend/cart.test.js#L26) | [env flag 2](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/961c0c476d4228a218859c658c42f9b6eebfdec4/tests/e2e/specs/backend/checkout.test.js#L26) | [env flag 3](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/961c0c476d4228a218859c658c42f9b6eebfdec4/tests/e2e/specs/backend/mini-cart.test.js#L18) | [env flag 4](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/961c0c476d4228a218859c658c42f9b6eebfdec4/tests/e2e/specs/backend/single-product.test.js#L8) | [env flag 5](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/961c0c476d4228a218859c658c42f9b6eebfdec4/tests/e2e/specs/frontend/cart.test.js#L29) | [env flag 6](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/961c0c476d4228a218859c658c42f9b6eebfdec4/tests/e2e/specs/frontend/checkout.test.js#L32)).

## Usages of `__experimental` prefix

### PHP filters and actions

-   `__experimental_woocommerce_blocks_payment_gateway_features_list` hook that allows modification of the features supported by PayPal Standard. ([experimental hook](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/4cedb65367be0d1c4c1f9dd9c016e3b1325cf92e/src/Payments/Integrations/PayPal.php#L86)).
-   **Deprecated** - `__experimental_woocommerce_blocks_checkout_update_order_meta` hook when the draft order has been created or updated from the cart and is now ready for extensions to modify the metadata ([experimental hook](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/3686/files#diff-af2c90fa556cc086b780c8fad99b68373d87fd6007e6e2ff1b4c68ebe9ccb551R377-R393)). [Deprecated in PR 5017](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/5017).
-   **Deprecated** - `__experimental_woocommerce_blocks_checkout_update_order_from_request` hook gives extensions the chance to update orders based on the data in the request ([deprecated experimental hook](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/d469a45d572f2c52d7917707c492dfb905ddfac0/src/StoreApi/Routes/Checkout.php#L466-L477)). [Deprecated in PR 5015](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/5015).
-   **Deprecated** - `__experimental_woocommerce_blocks_checkout_order_processed` hook when order has completed processing and is ready for payment ([deprecated experimental hook](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/accd1bbf402e043b9fc322f118ab614ba7437c92/src/StoreApi/Routes/Checkout.php#L237)). [Deprecated in PR 5014](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/5014).
-   `__experimental_woocommerce_blocks_add_data_attributes_to_namespace` hook that allows 3PD to add a namespace of blocks to receive block attributes as `data-` attributes ([experimental property](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/4a1ee97eb97011458174e93e44a9b7ad2f10ca36/src/BlockTypesController.php#L88)).
-   `__experimental_woocommerce_blocks_add_data_attributes_to_block` hook that allows 3PD to add a block to recieve block attributes as `data-` attributes ([experimental property](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/4a1ee97eb97011458174e93e44a9b7ad2f10ca36/src/BlockTypesController.php#L97)).

### JS methods

-   `__experimentalDeRegisterPaymentMethod` function used to deregister a payment method, only used in tests ([experimental function](https://github.com/woocommerce/woocommerce-blocks/blob/f27456dd00fa0b21b29a935943defb18351edf48/assets/js/blocks-registry/payment-methods/registry.ts#L110-L114)).
-   `__experimentalDeRegisterExpressPaymentMethod` function used to deregister an express payment method, only used in tests ([experimental function](https://github.com/woocommerce/woocommerce-blocks/blob/f27456dd00fa0b21b29a935943defb18351edf48/assets/js/blocks-registry/payment-methods/registry.ts#L116-L120)).

### Slots

-   `__experimentalOrderMeta` slot that allows extensions to add content to the order meta in the Cart and Checkout blocks ([experimental slot](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/4cedb65367be0d1c4c1f9dd9c016e3b1325cf92e/packages/checkout/order-meta/index.js#L12)).
-   `__experimentalOrderShippingPackages` slot that allows extensions to add content to the shipping packages in the Cart and Checkout blocks ([experimental slot](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/4cedb65367be0d1c4c1f9dd9c016e3b1325cf92e/packages/checkout/order-shipping-packages/index.js#L12)).
-   `__experimentalDiscountsMeta` slot that allows extensions to add content to the shipping packages in the Cart and Checkout blocks ([experimental slot](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/b6a9cc6342696f47cc08686522bdaca7989a6bc7/packages/checkout/discounts-meta/index.js)).

### Misc

-   `__experimental_woocommerce_blocks_hidden` property allows overwriting the `hidden` property for cart item data. This is useful to make some cart item data visible/hidden depending if it needs to be displayed in the Cart Block or the Cart Shortcode ([experimental property](https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/9c4288b0ee46960bdc2bf8ef351d05ac23073b0c/src/StoreApi/Schemas/CartItemSchema.php#L439-L441)). This was added in [this PR](https://github.com/woocommerce/woocommerce-blocks/pull/3732) to resolve [this issue with Subscriptions](https://github.com/woocommerce/woocommerce-blocks/issues/3731). This property will not be needed if the blocks replace the shortcode experience, since in that scenario, the `hidden` property would be sufficient.

## Usages of `experimental` prefix

`useStoreEvents` makes use of an `experimental__` prefix for wp-hook actions (since `__experimental` is not a valid prefix in that context).

-   `experimental__woocommerce_blocks-` is used for store events.
-   `experimental__woocommerce_blocks-checkout-` is used for checkout events.

Current list of events:

-   `experimental__woocommerce_blocks-cart-add-item` - Fired when an item is added to the cart.
-   `experimental__woocommerce_blocks-cart-set-item-quantity` - Fired when cart item quantity is changed by the customer.
-   `experimental__woocommerce_blocks-cart-remove-item` - Fired when a cart item is removed from the cart.
-   `experimental__woocommerce_blocks-product-view-link` - Fired when a product link is clicked.
-   `experimental__woocommerce_blocks-product-list-render` - Fired when a product list is rendered.
-   `experimental__woocommerce_blocks-product-search` - Fired when a search is submitted.
-   `experimental__woocommerce_blocks-store-notice-create` - Fired when a store notice is created.
-   `experimental__woocommerce_blocks-product-render` - Fired when a single product block is rendered.
-   `experimental__woocommerce_blocks-checkout-submit` - Fired when the checkout form is submitted.
-   `experimental__woocommerce_blocks-checkout-set-selected-shipping-rate` - Fired when a shipping rate is chosen on checkout.
-   `experimental__woocommerce_blocks-checkout-set-active-payment-method` - Fired when a payment method is chosen on checkout.
-   `experimental__woocommerce_blocks-checkout-render-checkout-form` - Fired when the checkout form is rendered.
-   `experimental__woocommerce_blocks-checkout-set-email-address` - Fired when an email address is added during checkout.
-   `experimental__woocommerce_blocks-checkout-set-shipping-address` - Fired when a shipping address is added during checkout.
-   `experimental__woocommerce_blocks-checkout-set-billing-address` - Fired when a billing address is added during checkout.
-   `experimental__woocommerce_blocks-checkout-set-phone-number` - Fired when a phone number is added during checkout.