Hide payment methods that have missing dependencies and display an error in the admin

docs/extensibility/payment-method-integration.md

@@ -136,7 +136,7 @@ In your class:
 -   Define an `initialize` function. This function will get called during the server side initialization process and is a good place to put any settings population etc. Basically anything you need to do to initialize your gateway. **Note, this will be called on every request so don't put anything expensive here.**
 -   Define an `is_active` function. This should return whether the payment method is active or not.
 -   Define a `get_payment_method_script_handles` function. In this function you should register your payment method scripts (using `wp_register_script`) and then return the script handles you registered with. This will be used to add your payment method as a dependency of the checkout script and thus take sure of loading it correctly. **Note:** You should still make sure any other asset dependencies your script has are registered properly here, if you're using Webpack to build your assets, you may want to use the [WooCommerce Webpack Dependency Extraction Plugin](https://www.npmjs.com/package/@woocommerce/dependency-extraction-webpack-plugin) to make this easier for you.
--   Define a `get_payment_method_script_handles_for_admin` function. Include this if your payment method has a script you _only_ want to load in the editor context for the checkout block.
+-   Define a `get_payment_method_script_handles_for_admin` function. Include this if your payment method has a script you _only_ want to load in the editor context for the checkout block. Include here any script from `get_payment_method_script_handles` that is also needed in the admin.
 -   Define a `get_payment_method_data` function. You can return from this function an associative array of data you want to be exposed for your payment method client side. This data will be available client side via `wc.wcSettings.getSetting`. So for instance if you assigned `stripe` as the value of the `name` property for this class, client side you can access any data via: `wc.wcSettings.getSetting( 'stripe_data' )`. That would return an object matching the shape of the associative array you returned from this function.
 
 ### Hooking into the Checkout processing by the Store API.

src/Payments/Api.php

@@ -52,6 +52,7 @@ protected function init() {
 		add_action( 'woocommerce_blocks_cart_enqueue_data', array( $this, 'add_payment_method_script_data' ) );
 		add_action( 'woocommerce_blocks_payment_method_type_registration', array( $this, 'register_payment_method_integrations' ) );
 		add_action( 'woocommerce_rest_checkout_process_payment_with_context', array( $this, 'process_legacy_payment' ), 999, 2 );
+		add_action( 'wp_print_scripts', array( $this, 'verify_payment_methods_dependencies' ), 1 );
 	}
 
 	/**
@@ -174,4 +175,55 @@ public function process_legacy_payment( PaymentContext $context, PaymentResult &
 		$result->set_payment_details( array_merge( $result->payment_details, $gateway_result ) );
 		$result->set_redirect_url( $gateway_result['redirect'] );
 	}
+
+	/**
+	 * Verify all dependencies of registered payment methods have been registered.
+	 * If not, remove that payment method script from the list of dependencies
+	 * of Cart and Checkout block scripts so it doesn't break the blocks and show
+	 * an error in the admin.
+	 */
+	public function verify_payment_methods_dependencies() {
+		$wp_scripts             = wp_scripts();
+		$payment_method_scripts = $this->payment_method_registry->get_all_active_payment_method_script_dependencies();
+
+		foreach ( $payment_method_scripts as $payment_method_script ) {
+			if (
+				! array_key_exists( $payment_method_script, $wp_scripts->registered ) ||
+				! property_exists( $wp_scripts->registered[ $payment_method_script ], 'deps' )
+			) {
+				continue;
+			}
+			$deps = $wp_scripts->registered[ $payment_method_script ]->deps;
+			foreach ( $deps as $dep ) {
+				if ( ! wp_script_is( $dep, 'registered' ) ) {
+					$error_handle  = $dep . '-dependency-error';
+					$error_message = sprintf(
+						'Payment gateway with handle \'%1$s\' has been deactivated because its dependency \'%2$s\' is not registered. Read the docs about registering assets for payment methods: https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/trunk/docs/extensibility/payment-method-integration.md#registering-assets',
+						esc_html( $payment_method_script ),
+						esc_html( $dep )
+					);
+
+					// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
+					error_log( $error_message );
+
+					// phpcs:ignore WordPress.WP.EnqueuedResourceParameters.NotInFooter,WordPress.WP.EnqueuedResourceParameters.MissingVersion
+					wp_register_script( $error_handle, '' );
+					wp_enqueue_script( $error_handle );
+					wp_add_inline_script(
+						$error_handle,
+						sprintf( 'console.error( "%s" );', $error_message )
+					);
+
+					$cart_checkout_scripts = [ 'wc-cart-block', 'wc-cart-block-frontend', 'wc-checkout-block', 'wc-checkout-block-frontend' ];
+					foreach ( $cart_checkout_scripts as $script_handle ) {
+						// Remove payment method script from dependencies.
+						$wp_scripts->registered[ $script_handle ]->deps = array_diff(
+							$wp_scripts->registered[ $script_handle ]->deps,
+							[ $payment_method_script ]
+						);
+					}
+				}
+			}
+		}
+	}
 }