Use recommended order currency API for multicurrency subscription renewal | switch | resubscribe

changelog/fix-4152-subscribe-renew-multicurrency-order-meta-api

@@ -0,0 +1,4 @@
+Significance: minor
+Type: fix
+
+Use high-level order currency API for multicurrency subscription renewal orders (get_post_meta is not recommended for orders).

includes/multi-currency/Compatibility/WooCommerceSubscriptions.php

@@ -148,7 +148,8 @@ public function override_selected_currency( $return ) {
 
 		$subscription_renewal = $this->cart_contains_renewal();
 		if ( $subscription_renewal ) {
-			return get_post_meta( $subscription_renewal['subscription_renewal']['renewal_order_id'], '_order_currency', true );
+			$order = wc_get_order( $subscription_renewal['subscription_renewal']['renewal_order_id'] );
+			return $order ? $order->get_currency() : $return;
 		}
 
 		$switch_id = $this->get_subscription_switch_id_from_superglobal();
@@ -158,13 +159,15 @@ public function override_selected_currency( $return ) {
 
 		$switch_cart_items = $this->get_subscription_switch_cart_items();
 		if ( 0 < count( $switch_cart_items ) ) {
-			$switch_cart_item = array_shift( $switch_cart_items );
-			return get_post_meta( $switch_cart_item['subscription_switch']['subscription_id'], '_order_currency', true );
+			$switch_cart_item    = array_shift( $switch_cart_items );
+			$switch_subscription = $this->get_subscription( $switch_cart_item['subscription_switch']['subscription_id'] );
+			return $switch_subscription ? $switch_subscription->get_currency() : $return;
 		}
 
 		$subscription_resubscribe = $this->cart_contains_resubscribe();
 		if ( $subscription_resubscribe ) {
-			return get_post_meta( $subscription_resubscribe['subscription_resubscribe']['subscription_id'], '_order_currency', true );
+			$subscription = $this->get_subscription( $subscription_resubscribe['subscription_resubscribe']['subscription_id'] );
+			return $subscription ? $subscription->get_currency() : $return;
 		}
 
 		return $return;
@@ -293,6 +296,21 @@ private function get_subscription_switch_cart_items(): array {
 		return wcs_get_order_type_cart_items( 'switch' );
 	}
 
+	/**
+	 * Getter for subscription objects.
+	 *
+	 * @param  mixed $the_subscription Post object or post ID of the order.
+	 * @return mixed The subscription object, or false if it cannot be found.
+	 *               Note: this is WC_Subscription|bool in normal use, but in tests
+	 *               we use WC_Order to simulate a subscription (hence `mixed`).
+	 */
+	private function get_subscription( $the_subscription ) {
+		if ( ! function_exists( 'wcs_get_subscription' ) ) {
+			return false;
+		}
+		return wcs_get_subscription( $the_subscription );
+	}
+
 	/**
 	 * Checks $_GET superglobal for a switch id and returns it if found.
 	 *