Issue #2897190 by MegaChriz, jonnyeom, bojanz, sagesolutions, edurenye, Hubbs,...

Issue #2897190 by MegaChriz, jonnyeom, bojanz, sagesolutions, edurenye, Hubbs, dev.tim: Tax calculations do not take discounts (promotions) into account

modules/promotion/commerce_promotion.services.yml

@@ -7,7 +7,7 @@ services:
     class: Drupal\commerce_promotion\PromotionOrderProcessor
     arguments: ['@entity_type.manager']
     tags:
-      - { name: commerce_order.order_processor, priority: 50, adjustment_type: promotion }
+      - { name: commerce_order.order_processor, priority: 100, adjustment_type: promotion }
 
   commerce_promotion.usage:
     class: Drupal\commerce_promotion\PromotionUsage

modules/tax/commerce_tax.services.yml

@@ -17,4 +17,4 @@ services:
     class: Drupal\commerce_tax\TaxOrderProcessor
     arguments: ['@entity_type.manager']
     tags:
-      - { name: commerce_order.order_processor, priority: 100, adjustment_type: tax }
+      - { name: commerce_order.order_processor, priority: 50, adjustment_type: tax }

modules/tax/src/Plugin/Commerce/TaxType/LocalTaxTypeBase.php

@@ -145,8 +145,10 @@ abstract class LocalTaxTypeBase extends TaxTypeBase implements LocalTaxTypeInter
 
       foreach ($rates as $zone_id => $rate) {
         $zone = $zones[$zone_id];
-        $unit_price = $order_item->getUnitPrice();
         $percentage = $rate->getPercentage();
+        // Determine the final unit price.
+        // This calculation must be done with a non-adjusted unit price.
+        $unit_price = $order_item->getUnitPrice();
         $tax_amount = $percentage->calculateTaxAmount($unit_price, $prices_include_tax);
         if ($this->shouldRound()) {
           $tax_amount = $this->rounder->round($tax_amount);
@@ -159,6 +161,14 @@ abstract class LocalTaxTypeBase extends TaxTypeBase implements LocalTaxTypeInter
           $unit_price = $unit_price->add($tax_amount);
           $order_item->setUnitPrice($unit_price);
         }
+        // Now determine the actual tax amount, with the adjustments applied.
+        $adjusted_unit_price = $order_item->getAdjustedUnitPrice(['promotion', 'fee']);
+        if (!$adjusted_unit_price->equals($unit_price)) {
+          $tax_amount = $percentage->calculateTaxAmount($adjusted_unit_price, $prices_include_tax);
+          if ($this->shouldRound()) {
+            $tax_amount = $this->rounder->round($tax_amount);
+          }
+        }
 
         $order_item->addAdjustment(new Adjustment([
           'type' => 'tax',

modules/tax/tests/src/Kernel/Plugin/Commerce/TaxType/CustomTest.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\commerce_tax\Kernel\Plugin\Commerce\TaxType;
 
+use Drupal\commerce_order\Adjustment;
 use Drupal\commerce_order\Entity\Order;
 use Drupal\commerce_order\Entity\OrderItem;
 use Drupal\commerce_order\Entity\OrderItemType;
@@ -188,6 +189,116 @@ class CustomTest extends CommerceKernelTestBase {
     $this->assertEquals(new Price('8.61', 'USD'), $order_item->getUnitPrice());
   }
 
+  /**
+   * @covers ::apply
+   */
+  public function testDiscountedPrices() {
+    // Tax-inclusive prices + display-inclusive taxes.
+    // A 10.33 USD price with a 1.00 USD discount should have a 9.33 USD total.
+    $order = $this->buildOrder('RS', 'RS', [], TRUE);
+    $order_items = $order->getItems();
+    $order_item = reset($order_items);
+    $order_item->addAdjustment(new Adjustment([
+      'type' => 'promotion',
+      'label' => t('Discount'),
+      'amount' => new Price('-1', 'USD'),
+    ]));
+    $this->plugin->apply($order);
+    $order_items = $order->getItems();
+    $order_item = reset($order_items);
+
+    $adjustments = $order->collectAdjustments();
+    $tax_adjustment = end($adjustments);
+    $this->assertCount(2, $adjustments);
+    $this->assertEquals('tax', $tax_adjustment->getType());
+    $this->assertEquals(t('VAT'), $tax_adjustment->getLabel());
+    $this->assertEquals(new Price('1.56', 'USD'), $tax_adjustment->getAmount());
+    $this->assertEquals('0.2', $tax_adjustment->getPercentage());
+    $this->assertEquals(new Price('10.33', 'USD'), $order_item->getUnitPrice());
+    $this->assertEquals(new Price('9.33', 'USD'), $order_item->getAdjustedUnitPrice());
+
+    // Non-tax-inclusive prices + display-inclusive taxes.
+    // A 10.33 USD price is 12.40 USD with 20% tax included.
+    // A 1.00 USD discount should result in a 11.40 USD total.
+    $order = $this->buildOrder('RS', 'RS', []);
+    $order_items = $order->getItems();
+    $order_item = reset($order_items);
+    $order_item->addAdjustment(new Adjustment([
+      'type' => 'promotion',
+      'label' => t('Discount'),
+      'amount' => new Price('-1', 'USD'),
+    ]));
+    $this->plugin->apply($order);
+    $order_items = $order->getItems();
+    $order_item = reset($order_items);
+
+    $adjustments = $order->collectAdjustments();
+    $tax_adjustment = end($adjustments);
+    $this->assertCount(2, $adjustments);
+    $this->assertEquals('tax', $tax_adjustment->getType());
+    $this->assertEquals(t('VAT'), $tax_adjustment->getLabel());
+    $this->assertEquals(new Price('2.28', 'USD'), $tax_adjustment->getAmount());
+    $this->assertEquals('0.2', $tax_adjustment->getPercentage());
+    $this->assertEquals(new Price('12.40', 'USD'), $order_item->getUnitPrice());
+    $this->assertEquals(new Price('11.40', 'USD'), $order_item->getAdjustedUnitPrice());
+
+    // Non-tax-inclusive prices + non-display-inclusive taxes.
+    // A 10.33 USD price with a 1.00 USD discount is 9.33 USD.
+    // And 9.33 USD plus 20% tax is 11.20 USD.
+    $configuration = $this->plugin->getConfiguration();
+    $configuration['display_inclusive'] = FALSE;
+    $this->plugin->setConfiguration($configuration);
+    $order = $this->buildOrder('RS', 'RS', []);
+    $order_items = $order->getItems();
+    $order_item = reset($order_items);
+    $order_item->addAdjustment(new Adjustment([
+      'type' => 'promotion',
+      'label' => t('Discount'),
+      'amount' => new Price('-1', 'USD'),
+    ]));
+    $this->plugin->apply($order);
+    $order_items = $order->getItems();
+    $order_item = reset($order_items);
+
+    $adjustments = $order->collectAdjustments();
+    $tax_adjustment = end($adjustments);
+    $this->assertCount(2, $adjustments);
+    $this->assertEquals('tax', $tax_adjustment->getType());
+    $this->assertEquals(t('VAT'), $tax_adjustment->getLabel());
+    $this->assertEquals(new Price('1.87', 'USD'), $tax_adjustment->getAmount());
+    $this->assertEquals('0.2', $tax_adjustment->getPercentage());
+    $this->assertEquals(new Price('10.33', 'USD'), $order_item->getUnitPrice());
+    $this->assertEquals(new Price('11.20', 'USD'), $order_item->getAdjustedUnitPrice());
+
+    // Tax-inclusive prices + non-display-inclusive taxes.
+    // A 10.33 USD price is 8.61 USD once the 20% tax is removed.
+    // A 1.00 USD discount gives 7.61 USD + 20% VAT -> 8.88 USD.
+    $configuration = $this->plugin->getConfiguration();
+    $configuration['display_inclusive'] = FALSE;
+    $this->plugin->setConfiguration($configuration);
+    $order = $this->buildOrder('RS', 'RS', [], TRUE);
+    $order_items = $order->getItems();
+    $order_item = reset($order_items);
+    $order_item->addAdjustment(new Adjustment([
+      'type' => 'promotion',
+      'label' => t('Discount'),
+      'amount' => new Price('-1', 'USD'),
+    ]));
+    $this->plugin->apply($order);
+    $order_items = $order->getItems();
+    $order_item = reset($order_items);
+
+    $adjustments = $order->collectAdjustments();
+    $tax_adjustment = end($adjustments);
+    $this->assertCount(2, $adjustments);
+    $this->assertEquals('tax', $tax_adjustment->getType());
+    $this->assertEquals(t('VAT'), $tax_adjustment->getLabel());
+    $this->assertEquals(new Price('1.27', 'USD'), $tax_adjustment->getAmount());
+    $this->assertEquals('0.2', $tax_adjustment->getPercentage());
+    $this->assertEquals(new Price('8.61', 'USD'), $order_item->getUnitPrice());
+    $this->assertEquals(new Price('8.88', 'USD'), $order_item->getAdjustedUnitPrice());
+  }
+
   /**
    * @covers ::apply
    */