Refactor Order Class to use shared calculation logic.

We added a trait to move shared logic betweem Orders and Cart. This commit refactors Order class to use that shared logic.
Also adds a test for a failing case.

includes/abstracts/abstract-wc-order.php

@@ -18,6 +18,7 @@ require_once WC_ABSPATH . 'includes/legacy/abstract-wc-legacy-order.php';
  * WC_Abstract_Order class.
  */
 abstract class WC_Abstract_Order extends WC_Abstract_Legacy_Order {
+	use WC_Item_Totals;
 
 	/**
 	 * Order Data array. This is the core order data exposed in APIs since 3.0.0.
@@ -769,6 +770,23 @@ abstract class WC_Abstract_Order extends WC_Abstract_Legacy_Order {
 		return apply_filters( 'woocommerce_order_get_items', $items, $this, $types );
 	}
 
+	/**
+	 * Return array of values for calculations.
+	 *
+	 * @param string $field Field name to return.
+	 *
+	 * @return array Array of values.
+	 */
+	protected function get_values_for_total( $field ) {
+		$items = array_map(
+			function ( $item ) use ( $field ) {
+				return wc_add_number_precision( $item[ $field ] );
+			},
+			array_values( $this->get_items() )
+		);
+		return $items;
+	}
+
 	/**
 	 * Return an array of coupons within this order.
 	 *
@@ -1508,18 +1526,13 @@ abstract class WC_Abstract_Order extends WC_Abstract_Legacy_Order {
 	public function calculate_totals( $and_taxes = true ) {
 		do_action( 'woocommerce_order_before_calculate_totals', $and_taxes, $this );
 
-		$cart_subtotal     = 0;
-		$cart_total        = 0;
 		$fees_total        = 0;
 		$shipping_total    = 0;
 		$cart_subtotal_tax = 0;
 		$cart_total_tax    = 0;
 
-		// Sum line item costs.
-		foreach ( $this->get_items() as $item ) {
-			$cart_subtotal += round( $item->get_subtotal(), wc_get_price_decimals() );
-			$cart_total    += round( $item->get_total(), wc_get_price_decimals() );
-		}
+		$cart_subtotal = wc_remove_number_precision( $this->get_rounded_items_total( 'subtotal' ) );
+		$cart_total = wc_remove_number_precision( $this->get_rounded_items_total() );
 
 		// Sum shipping costs.
 		foreach ( $this->get_shipping_methods() as $shipping ) {

includes/class-wc-cart-totals.php

@@ -553,6 +553,16 @@ final class WC_Cart_Totals {
 		return $in_cents ? $this->totals : wc_remove_number_precision_deep( $this->totals );
 	}
 
+	/**
+	 * Returns array of values for totals calculation.
+	 *
+	 * @param string $field Field name. Will probably be `total` or `subtotal`.
+	 * @return array Items object
+	 */
+	protected function get_values_for_total( $field ) {
+		return array_values( wp_list_pluck( $this->items, $field ) );
+	}
+
 	/**
 	 * Get taxes merged by type.
 	 *

includes/traits/trait-wc-item-totals.php

@@ -13,24 +13,28 @@ if ( ! defined( 'ABSPATH' ) ) {
 /**
  * Trait WC_Item_Totals.
  *
+ * Right now this do not have much, but plan is to eventually move all shared calculation logic between Orders and Cart in this file.
+ *
  * @since 3.9.0
  */
 trait WC_Item_Totals {
 
 	/**
-	 * Line items to calculate. Overwrite in child class.
+	 * Line items to calculate. Define in child class.
 	 *
 	 * @since 3.9.0
-	 * @var WC_Order_Item[]
+	 * @param string $field Field name to calculate upon.
+	 *
+	 * @return array having `total`|`subtotal` property.
 	 */
-	protected $items = array();
+	abstract protected function get_values_for_total( $field );
 
 	/**
 	 * Return rounded total based on settings. Will be used by Cart and Orders.
 	 *
 	 * @since 3.9.0
 	 *
-	 * @param string $field Field to round and sum based on setting. Will likely be `total` or `subtotal`.
+	 * @param string $field Field to round and sum based on setting. Will likely be `total` or `subtotal`. Values must be without precision.
 	 *
 	 * @return float|int Appropriately rounded value.
 	 */
@@ -38,7 +42,7 @@ trait WC_Item_Totals {
 		return array_sum(
 			array_map(
 				array( $this, 'round_item_subtotal' ),
-				array_values( wp_list_pluck( $this->items, $field ) )
+				$this->get_values_for_total( $field )
 			)
 		);
 	}

tests/unit-tests/order/class-wc-tests-orders.php

@@ -0,0 +1,55 @@
+<?php
+/**
+ * Class WC_Tests_Order file.
+ *
+ * @package WooCommerce|Tests|Order
+ */
+
+/**
+ * Class WC_Tests_Order.
+ */
+class WC_Tests_Order extends WC_Unit_Test_Case {
+
+	/**
+	 * Test for total when round at subtotal is enabled.
+	 *
+	 * @link https://github.com/woocommerce/woocommerce/issues/24695
+	 */
+	public function test_order_calculate_total_rounding_24695() {
+		update_option( 'woocommerce_prices_include_tax', 'yes' );
+		update_option( 'woocommerce_calc_taxes', 'yes' );
+		update_option( 'woocommerce_tax_round_at_subtotal', 'yes' );
+
+		$tax_rate    = array(
+			'tax_rate_country'  => '',
+			'tax_rate_state'    => '',
+			'tax_rate'          => '7.0000',
+			'tax_rate_name'     => 'CGST',
+			'tax_rate_priority' => '1',
+			'tax_rate_compound' => '0',
+			'tax_rate_shipping' => '0',
+			'tax_rate_order'    => '1',
+			'tax_rate_class'    => 'tax_1',
+		);
+		WC_Tax::_insert_tax_rate( $tax_rate );
+
+		$product1 = WC_Helper_Product::create_simple_product();
+		$product1->set_regular_price( 2 );
+		$product1->save();
+
+		$product2 = WC_Helper_Product::create_simple_product();
+		$product2->set_regular_price( 2.5 );
+		$product2->save();
+
+		$order = new WC_Order();
+		$order->add_product( $product1, 1 );
+		$order->add_product( $product2, 4 );
+		$order->save();
+
+		$order->calculate_totals( true );
+
+		$this->assertEquals( 12, $order->get_total() );
+		$this->assertEquals( 0.79, $order->get_total_tax() );
+	}
+
+}

tests/unit-tests/order/coupons.php

@@ -62,7 +62,7 @@ class WC_Tests_Order_Coupons extends WC_Unit_Test_Case {
 				array(
 					'product'  => $product,
 					'quantity' => 1,
-					'subtotal' => 909.09, // Ex tax.
+					'subtotal' => 909.09, // Ex tax 10%.
 					'total'    => 726.36,
 				)
 			);