Add notices about the removal of the Legacy API in WooCommerce 9.0

- A permanent notice in Settings - Advanced - Legacy API

- A dismissable admin notice only if the Legacy API is enabled
  (disappears if it gets disabled)

plugins/woocommerce/includes/admin/class-wc-admin-notices.php

@@ -7,6 +7,7 @@
  */
 
 use Automattic\Jetpack\Constants;
+use Automattic\WooCommerce\Internal\Traits\AccessiblePrivateMethods;
 use Automattic\WooCommerce\Internal\Utilities\Users;
 
 defined( 'ABSPATH' ) || exit;
@@ -16,6 +17,8 @@ defined( 'ABSPATH' ) || exit;
  */
 class WC_Admin_Notices {
 
+	use AccessiblePrivateMethods;
+
 	/**
 	 * Stores notices.
 	 *
@@ -53,6 +56,7 @@ class WC_Admin_Notices {
 		add_action( 'woocommerce_installed', array( __CLASS__, 'reset_admin_notices' ) );
 		add_action( 'wp_loaded', array( __CLASS__, 'add_redirect_download_method_notice' ) );
 		add_action( 'admin_init', array( __CLASS__, 'hide_notices' ), 20 );
+		self::add_action( 'admin_init', array( __CLASS__, 'maybe_remove_legacy_api_removal_notice' ), 20 );
 
 		// @TODO: This prevents Action Scheduler async jobs from storing empty list of notices during WC installation.
 		// That could lead to OBW not starting and 'Run setup wizard' notice not appearing in WP admin, which we want
@@ -115,6 +119,46 @@ class WC_Admin_Notices {
 		self::add_notice( 'template_files' );
 		self::add_min_version_notice();
 		self::add_maxmind_missing_license_key_notice();
+		self::maybe_add_legacy_api_removal_notice();
+	}
+
+	/**
+	 * Add an admin notice about the removal of the Legacy REST API if the said API is enabled.
+	 *
+	 * TODO: Remove this method in WooCommerce 9.0.
+	 */
+	private static function maybe_add_legacy_api_removal_notice() {
+		if ( 'yes' !== get_option( 'woocommerce_api_enabled' ) ) {
+			return;
+		}
+
+		self::add_custom_notice(
+			'legacy_api_removed_in_woo_90',
+			sprintf(
+				'%s%s',
+				sprintf(
+					'<h4>%s</h4>',
+					esc_html__( 'WooCommerce Legacy API to be removed soon', 'woocommerce' )
+				),
+				sprintf(
+					// translators: Placeholders are URLs.
+					wpautop( wp_kses_data( __( 'The WooCommerce Legacy REST API, <a href="%1$s">currently enabled in this site</a>, will be removed in WooCommerce 9.0. A separate WooCommerce extension will be available to re-enable it. <b><a target=”_blank” href="%2$s">Learn more about this change</a></b>', 'woocommerce' ) ) ),
+					admin_url( 'admin.php?page=wc-settings&tab=advanced&section=legacy_api' ),
+					'https://developer.woocommerce.com/2023/10/03/the-legacy-rest-api-will-move-to-a-dedicated-extension-in-woocommerce-9-0/'
+				)
+			)
+		);
+	}
+
+	/**
+	 * Remove the admin notice about the removal of the Legacy REST API if the said API is disabled.
+	 *
+	 * TODO: Remove this method in WooCommerce 9.0.
+	 */
+	private static function maybe_remove_legacy_api_removal_notice() {
+		if ( 'yes' !== get_option( 'woocommerce_api_enabled' ) && self::has_notice( 'legacy_api_removed_in_woo_90' ) ) {
+			self::remove_notice( 'legacy_api_removed_in_woo_90' );
+		}
 	}
 
 	/**
@@ -424,7 +468,7 @@ class WC_Admin_Notices {
 
 	/**
 	 * Notice about WordPress and PHP minimum requirements.
-	 * 
+	 *
 	 * @deprecated 8.2.0 WordPress and PHP minimum requirements notices are no longer shown.
 	 *
 	 * @since 3.6.5

plugins/woocommerce/includes/admin/settings/class-wc-settings-advanced.php

@@ -392,11 +392,19 @@ class WC_Settings_Advanced extends WC_Settings_Page {
 					'id'    => 'legacy_api_options',
 				),
 				array(
-					'title'   => __( 'Legacy API', 'woocommerce' ),
-					'desc'    => __( 'Enable the legacy REST API', 'woocommerce' ),
-					'id'      => 'woocommerce_api_enabled',
-					'type'    => 'checkbox',
-					'default' => 'no',
+					'title'    => __( 'Legacy API', 'woocommerce' ),
+					'desc'     => __( 'Enable the legacy REST API', 'woocommerce' ),
+					'id'       => 'woocommerce_api_enabled',
+					'type'     => 'checkbox',
+					'default'  => 'no',
+					'desc_tip' => sprintf(
+						// translators: Placeholder is a URL.
+						__(
+							'⚠<b>️ The Legacy REST API will be removed in WooCommerce 9.0.</b> A separate WooCommerce extension will be available to re-enable it. <b><a target=”_blank” href="%s">Learn more about this change</a></b>',
+							'woocommerce'
+						),
+						'https://developer.woocommerce.com/2023/10/03/the-legacy-rest-api-will-move-to-a-dedicated-extension-in-woocommerce-9-0/'
+					),
 				),
 				array(
 					'type' => 'sectionend',