Do not change shipping costs structure when applying multi-currency presentation (#10778)

Author: dmvrtx

changelog/woopmnt-4977-cannot-tax-shipping-when-woopayments-is-the-payment-gateway

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Keep the shipping costs structure intact when applying multi-currency adjustments.

includes/multi-currency/FrontendPrices.php

@@ -275,13 +275,24 @@ public function add_exchange_rate_to_variation_prices_hash( $prices_hash ) {
 	 * @return array Shipping rate args with converted cost.
 	 */
 	public function convert_shipping_method_rate_cost( $args ) {
-		$cost = is_array( $args['cost'] ) ? array_sum( $args['cost'] ) : $args['cost'];
-		$args = wp_parse_args(
-			[
-				'cost' => $this->multi_currency->get_price( $cost, 'shipping' ),
-			],
-			$args
-		);
+		if ( isset( $args['cost'] ) ) {
+			/**
+			 * We need to keep the `cost` structure intact when applying
+			 * multi-currency conversions, because downstream it is important
+			 * for WooCommerce to keep the taxes flow consistent.
+			 */
+			if ( is_array( $args['cost'] ) ) {
+				$args['cost'] = array_map(
+					function ( $cost ) {
+						return $this->multi_currency->get_price( $cost, 'shipping' );
+					},
+					$args['cost']
+				);
+			} else {
+				$args['cost'] = $this->multi_currency->get_price( $args['cost'], 'shipping' );
+			}
+		}
+
 		return $args;
 	}
 

tests/unit/multi-currency/test-class-frontend-prices.php

@@ -233,11 +233,23 @@ function () {
 	}
 
 	public function test_convert_shipping_method_rate_cost_for_array_cost() {
+		$matcher = $this->exactly( 2 );
 		$this->mock_multi_currency
-			->expects( $this->once() )
+			->expects( $matcher )
 			->method( 'get_price' )
-			->with( '11' )
-			->willReturn( 25.0 );
+			->willReturnCallback(
+				function ( $price ) use ( $matcher ) {
+					switch ( $matcher->getInvocationCount() ) {
+						case 1:
+							$this->assertEquals( 10.0, $price );
+							break;
+						case 2:
+							$this->assertEquals( 1.0, $price );
+							break;
+					}
+					return $price;
+				}
+			);
 
 		add_filter( 'wc_tax_enabled', '__return_true' );
 		add_filter(
@@ -272,8 +284,8 @@ function () {
 		$shipping_rate = $shipping_method->rates[1];
 
 		// Cost gets converted and taxes properly calculated based on it.
-		$this->assertSame( '25.00', $shipping_rate->cost );
-		$this->assertSame( 2.5, $shipping_rate->taxes[1] );
+		$this->assertSame( '11.00', $shipping_rate->cost );
+		$this->assertSame( 1.1, $shipping_rate->taxes[1] );
 	}
 
 	public function test_get_coupon_amount_returns_empty_amount() {