add currency code to cart and checkout block totals when mccy is enabled

changelog/fix-total-amounts-not-displayed-with-explicit-currency-code

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Make sure an explicit currency code is present in the cart and checkout blocks when multi-currency is enabled

client/checkout/blocks/index.js

@@ -11,7 +11,7 @@ import {
 /**
  * Internal dependencies
  */
-import { getUPEConfig } from 'utils/checkout';
+import { getUPEConfig, getConfig } from 'utils/checkout';
 import { isLinkEnabled } from '../utils/upe';
 import WCPayAPI from '../api';
 import { SavedTokenHandler } from './saved-token-handler';
@@ -158,3 +158,22 @@ window.addEventListener( 'load', () => {
 	enqueueFraudScripts( getUPEConfig( 'fraudServices' ) );
 	addCheckoutTracking();
 } );
+
+// If multi-currency is enabled, add currency code to total amount in cart and checkout blocks.
+if ( getConfig( 'isMultiCurrencyEnabled' ) ) {
+	const { registerCheckoutFilters } = window.wc.blocksCheckout;
+
+	const modifyTotalsPrice = ( defaultValue, extensions, args ) => {
+		const { cart } = args;
+
+		if ( cart?.cartTotals?.currency_code ) {
+			return `<price/> ${ cart.cartTotals.currency_code }`;
+		}
+
+		return defaultValue;
+	};
+
+	registerCheckoutFilters( 'woocommerce-payments', {
+		totalValue: modifyTotalsPrice,
+	} );
+}

includes/multi-currency/MultiCurrency.php

@@ -252,6 +252,8 @@ public function init_hooks() {
 			add_action( 'woocommerce_created_customer', [ $this, 'set_new_customer_currency_meta' ] );
 		}
 
+		add_filter( 'wcpay_payment_fields_js_config', [ $this, 'add_props_to_wcpay_js_config' ] );
+
 		$this->currency_switcher_block->init_hooks();
 	}
 
@@ -388,6 +390,19 @@ public function enqueue_admin_scripts() {
 		WC_Payments_Utils::enqueue_style( 'WCPAY_MULTI_CURRENCY_SETTINGS' );
 	}
 
+	/**
+	 * Add multi-currency specific props to the WCPay JS config.
+	 *
+	 * @param  array $config The JS config that will be loaded on the frontend.
+	 *
+	 * @return array  The updated JS config.
+	 */
+	public function add_props_to_wcpay_js_config( $config ) {
+		$config['isMultiCurrencyEnabled'] = true;
+
+		return $config;
+	}
+
 	/**
 	 * Wipes the cached currency data option, forcing to re-fetch the data from WPCOM.
 	 *