<form method="POST">
    <h3>Editing: CartSelectShippingRate.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
namespace Automattic\WooCommerce\StoreApi\Routes\V1;

use Automattic\WooCommerce\StoreApi\Exceptions\RouteException;

/**
 * CartSelectShippingRate class.
 */
class CartSelectShippingRate extends AbstractCartRoute {
	/**
	 * The route identifier.
	 *
	 * @var string
	 */
	const IDENTIFIER = 'cart-select-shipping-rate';

	/**
	 * Get the path of this REST route.
	 *
	 * @return string
	 */
	public function get_path() {
		return self::get_path_regex();
	}

	/**
	 * Get the path of this rest route.
	 *
	 * @return string
	 */
	public static function get_path_regex() {
		return '/cart/select-shipping-rate';
	}

	/**
	 * Get method arguments for this REST route.
	 *
	 * @return array An array of endpoints.
	 */
	public function get_args() {
		return [
			[
				'methods'             =&gt; \WP_REST_Server::CREATABLE,
				'callback'            =&gt; [ $this, 'get_response' ],
				'permission_callback' =&gt; '__return_true',
				'args'                =&gt; [
					'package_id' =&gt; array(
						'description' =&gt; __( 'The ID of the package being shipped. Leave blank to apply to all packages.', 'woocommerce' ),
						'type'        =&gt; [ 'integer', 'string', 'null' ],
						'required'    =&gt; false,
					),
					'rate_id'    =&gt; [
						'description' =&gt; __( 'The chosen rate ID for the package.', 'woocommerce' ),
						'type'        =&gt; 'string',
						'required'    =&gt; true,
					],
				],
			],
			'schema'      =&gt; [ $this-&gt;schema, 'get_public_item_schema' ],
			'allow_batch' =&gt; [ 'v1' =&gt; true ],
		];
	}

	/**
	 * Handle the request and return a valid response for this endpoint.
	 *
	 * @throws RouteException On error.
	 * @param \WP_REST_Request $request Request object.
	 * @return \WP_REST_Response
	 */
	protected function get_route_post_response( \WP_REST_Request $request ) {
		if ( ! wc_shipping_enabled() ) {
			throw new RouteException( 'woocommerce_rest_shipping_disabled', esc_html__( 'Shipping is disabled.', 'woocommerce' ), 404 );
		}

		if ( ! isset( $request['rate_id'] ) ) {
			throw new RouteException( 'woocommerce_rest_cart_missing_rate_id', esc_html__( 'Invalid Rate ID.', 'woocommerce' ), 400 );
		}

		$cart       = $this-&gt;cart_controller-&gt;get_cart_instance();
		$package_id = isset( $request['package_id'] ) ? sanitize_text_field( wp_unslash( $request['package_id'] ) ) : null;
		$rate_id    = sanitize_text_field( wp_unslash( $request['rate_id'] ) );

		try {
			if ( ! is_null( $package_id ) ) {
				$this-&gt;cart_controller-&gt;select_shipping_rate( $package_id, $rate_id );
			} else {
				foreach ( $this-&gt;cart_controller-&gt;get_shipping_packages() as $package ) {
					$this-&gt;cart_controller-&gt;select_shipping_rate( $package['package_id'], $rate_id );
				}
			}
		} catch ( \WC_Rest_Exception $e ) {
			throw new RouteException( $e-&gt;getErrorCode(), $e-&gt;getMessage(), $e-&gt;getCode() ); // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
		}

		/**
		 * Fires an action after a shipping method has been chosen for package(s) via the Store API.
		 *
		 * This allows extensions to perform addition actions after a shipping method has been chosen, but before the
		 * cart totals are recalculated.
		 *
		 * @since 9.0.0
		 *
		 * @param string|null $package_id The sanitized ID of the package being updated. Null if all packages are being updated.
		 * @param string $rate_id The sanitized chosen rate ID for the package.
		 * @param \WP_REST_Request $request Full details about the request.
		 */
		do_action( 'woocommerce_store_api_cart_select_shipping_rate', $package_id, $rate_id, $request );

		$cart-&gt;calculate_totals();

		return rest_ensure_response( $this-&gt;cart_schema-&gt;get_item_response( $cart ) );
	}
}
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