Use site language when making Store API requests in Cart/Checkout (#51244)

* Use correct langauge by reseting the locale param

* use typescript

plugins/woocommerce-blocks/assets/js/middleware/index.js

@@ -2,3 +2,4 @@
  * Internal dependencies
  */
 import './store-api-nonce';
+import './remove-user-locale';

plugins/woocommerce-blocks/assets/js/middleware/remove-user-locale.ts

@@ -0,0 +1,38 @@
+/**
+ * External dependencies
+ */
+import apiFetch from '@wordpress/api-fetch';
+import { addQueryArgs } from '@wordpress/url';
+
+/**
+ * Internal dependencies
+ */
+import { isStoreApiRequest } from './store-api-nonce';
+
+/**
+ * Middleware to add the '_locale=site' query parameter from API requests.
+ *
+ * TODO: Remove once https://github.com/WordPress/gutenberg/issues/16805 is fixed and replace by removing userLocaleMiddleware middleware.
+ *
+ * @param {Object}   options      Fetch options.
+ * @param {Object}   options.url  The URL of the request.
+ * @param {Object}   options.path The path of the request.
+ * @param {Function} next         The next middleware or fetchHandler to call.
+ * @return {*} The evaluated result of the remaining middleware chain.
+ */
+const removeUserLocaleMiddleware = (
+	options: { url?: string; path?: string },
+	next: ( options: { url?: string; path?: string } ) => Promise< unknown >
+): Promise< unknown > => {
+	if ( typeof options.url === 'string' && isStoreApiRequest( options ) ) {
+		options.url = addQueryArgs( options.url, { _locale: 'site' } );
+	}
+
+	if ( typeof options.path === 'string' && isStoreApiRequest( options ) ) {
+		options.path = addQueryArgs( options.path, { _locale: 'site' } );
+	}
+
+	return next( options );
+};
+
+apiFetch.use( removeUserLocaleMiddleware );

plugins/woocommerce-blocks/assets/js/middleware/store-api-nonce.js

@@ -23,7 +23,7 @@ try {
  *
  * @return {boolean} Returns true if this is a store request.
  */
-const isStoreApiRequest = ( options ) => {
+export const isStoreApiRequest = ( options ) => {
 	const url = options.url || options.path;
 	if ( ! url || ! options.method || options.method === 'GET' ) {
 		return false;

plugins/woocommerce/changelog/fix-correct-language-in-frontend

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Use the correct language in Cart/Checkout when the user language is different from the store.