[Bugfix] Incorrect Unit Net Price

UPGRADE-2.2.md

@@ -72,3 +72,16 @@
    | `Sylius\InvoicingPlugin\Manager\InvoiceFileManager`             | `Sylius\PdfGenerationBundle\Core\Filesystem\Manager\PdfFileManager`          |
 
    The corresponding services (`sylius_invoicing.generator.twig_to_pdf` and `sylius_invoicing.generator.pdf_options`) are also deprecated.
+
+1. `Sylius\InvoicingPlugin\Provider\UnitNetPriceProvider` now accepts a `CalculatorInterface` argument used to compute the
+   tax included in the unit price. Not passing it is deprecated and it will be required in 3.0:
+
+    ```diff
+    public function __construct(
+    +   private ?CalculatorInterface $taxCalculator = null,
+    )
+    ```
+
+   When no calculator is passed, the provider falls back to recalculating the included tax from the full unit price.
+   This replaces the previous behaviour of subtracting the neutral tax adjustment amount directly, which was computed on
+   the discounted (post-promotion) price and therefore produced a net price that diverged from the actual one.

config/services.xml

@@ -71,7 +71,9 @@
         <service
             id="sylius_invoicing.provider.unit_net_price"
             class="Sylius\InvoicingPlugin\Provider\UnitNetPriceProvider"
-        />
+        >
+            <argument type="service" id="sylius.tax_calculator.default" />
+        </service>
         <service id="Sylius\InvoicingPlugin\Provider\UnitNetPriceProviderInterface" alias="sylius_invoicing.provider.unit_net_price" />
     </services>
 </container>

features/managing_invoices/seeing_invoice_with_taxes_included_in_price_and_promotions_applied.feature

@@ -22,6 +22,6 @@ Feature: Seeing included in price taxes and promotions applied on an invoice
 
     Scenario: Seeing proper taxes and promotions on an invoice
         When I view the summary of the invoice for order "#00000666"
-        Then it should have 2 "PHP T-Shirt" items with unit net price "50.65", discounted unit net price "40.65", net value "81.30", tax total "18.70" and total "100.00" in "USD" currency
+        Then it should have 2 "PHP T-Shirt" items with unit net price "48.78", discounted unit net price "40.65", net value "81.30", tax total "18.70" and total "100.00" in "USD" currency
         And it should have a tax item "23%" with amount "18.70" in "USD" currency
         And its total should be "110.00" in "USD" currency

src/Provider/UnitNetPriceProvider.php

@@ -15,20 +15,52 @@
 
 use Sylius\Component\Core\Model\AdjustmentInterface;
 use Sylius\Component\Core\Model\OrderItemUnitInterface;
+use Sylius\Component\Taxation\Calculator\CalculatorInterface;
+use Sylius\Component\Taxation\Model\TaxRate;
 
 final class UnitNetPriceProvider implements UnitNetPriceProviderInterface
 {
+    public function __construct(
+        private ?CalculatorInterface $taxCalculator = null,
+    ) {
+        if (null === $taxCalculator) {
+            trigger_deprecation(
+                'sylius/invoicing-plugin',
+                '2.2',
+                'Not passing a "%s" instance to "%s" is deprecated and it will be required in 3.0.',
+                CalculatorInterface::class,
+                self::class,
+            );
+        }
+    }
+
     public function getUnitNetPrice(OrderItemUnitInterface $orderItemUnit): int
     {
         $orderItem = $orderItemUnit->getOrderItem();
         $unitPrice = $orderItem->getUnitPrice();
         /** @var AdjustmentInterface $adjustment */
         foreach ($orderItemUnit->getAdjustments(AdjustmentInterface::TAX_ADJUSTMENT) as $adjustment) {
             if ($adjustment->isNeutral()) {
-                $unitPrice -= $adjustment->getAmount();
+                /** @var float $taxRateAmount */
+                $taxRateAmount = $adjustment->getDetails()['taxRateAmount'];
+
+                $unitPrice -= $this->calculateIncludedTax($unitPrice, $taxRateAmount);
             }
         }
 
         return $unitPrice;
     }
+
+    private function calculateIncludedTax(int $unitPrice, float $taxRateAmount): int
+    {
+        if (null !== $this->taxCalculator) {
+            $taxRate = new TaxRate();
+            $taxRate->setAmount($taxRateAmount);
+            $taxRate->setIncludedInPrice(true);
+
+            return (int) round($this->taxCalculator->calculate($unitPrice, $taxRate));
+        }
+
+        return (int) round($unitPrice - ($unitPrice / (1 + $taxRateAmount)));
+    }
 }

tests/Unit/Provider/UnitNetPriceProviderTest.php

@@ -19,6 +19,7 @@
 use Sylius\Component\Core\Model\AdjustmentInterface;
 use Sylius\Component\Core\Model\OrderItemInterface;
 use Sylius\Component\Core\Model\OrderItemUnitInterface;
+use Sylius\Component\Taxation\Calculator\DefaultCalculator;
 use Sylius\InvoicingPlugin\Provider\UnitNetPriceProvider;
 use Sylius\InvoicingPlugin\Provider\UnitNetPriceProviderInterface;
 
@@ -29,7 +30,7 @@ final class UnitNetPriceProviderTest extends TestCase
     protected function setUp(): void
     {
         parent::setUp();
-        $this->provider = new UnitNetPriceProvider();
+        $this->provider = new UnitNetPriceProvider(new DefaultCalculator());
     }
 
     #[Test]
@@ -54,13 +55,112 @@ public function it_provides_net_price_for_unit_with_taxes_included_in_price(): v
             ->willReturn(new ArrayCollection([$taxAdjustment]));
 
         $taxAdjustment->method('isNeutral')->willReturn(true);
-        $taxAdjustment->method('getAmount')->willReturn(200);
+        $taxAdjustment->method('getDetails')->willReturn(['taxRateAmount' => 0.25]);
 
         $result = $this->provider->getUnitNetPrice($unit);
 
         self::assertSame(800, $result);
     }
 
+    #[Test]
+    public function it_provides_net_price_for_unit_with_taxes_included_in_price_and_promotion_applied(): void
+    {
+        $unit = $this->createMock(OrderItemUnitInterface::class);
+        $orderItem = $this->createMock(OrderItemInterface::class);
+        $taxAdjustment = $this->createMock(AdjustmentInterface::class);
+
+        $unit->method('getOrderItem')->willReturn($orderItem);
+        $orderItem->method('getUnitPrice')->willReturn(12000);
+
+        $unit
+            ->method('getAdjustments')
+            ->with(AdjustmentInterface::TAX_ADJUSTMENT)
+            ->willReturn(new ArrayCollection([$taxAdjustment]));
+
+        // Neutral tax adjustment: amount is calculated on discounted price (post-promotion),
+        // so using getAmount() directly would give a wrong result.
+        $taxAdjustment->method('isNeutral')->willReturn(true);
+        $taxAdjustment->method('getDetails')->willReturn(['taxRateAmount' => 0.20]);
+
+        $result = $this->provider->getUnitNetPrice($unit);
+
+        self::assertSame(10000, $result);
+    }
+
+    #[Test]
+    public function it_triggers_a_deprecation_and_calculates_the_tax_manually_when_no_calculator_is_passed(): void
+    {
+        $deprecation = null;
+        set_error_handler(static function (int $errno, string $errstr) use (&$deprecation): bool {
+            $deprecation = $errstr;
+
+            return true;
+        }, \E_USER_DEPRECATED);
+
+        try {
+            $provider = new UnitNetPriceProvider();
+        } finally {
+            restore_error_handler();
+        }
+
+        self::assertNotNull($deprecation);
+        self::assertStringContainsString('will be required in 3.0', $deprecation);
+
+        $unit = $this->createMock(OrderItemUnitInterface::class);
+        $orderItem = $this->createMock(OrderItemInterface::class);
+        $taxAdjustment = $this->createMock(AdjustmentInterface::class);
+
+        $unit->method('getOrderItem')->willReturn($orderItem);
+        $orderItem->method('getUnitPrice')->willReturn(1000);
+
+        $unit
+            ->method('getAdjustments')
+            ->with(AdjustmentInterface::TAX_ADJUSTMENT)
+            ->willReturn(new ArrayCollection([$taxAdjustment]));
+
+        $taxAdjustment->method('isNeutral')->willReturn(true);
+        $taxAdjustment->method('getDetails')->willReturn(['taxRateAmount' => 0.25]);
+
+        self::assertSame(800, $provider->getUnitNetPrice($unit));
+    }
+
+    #[Test]
+    public function it_calculates_the_tax_manually_on_the_full_unit_price_when_no_calculator_is_passed_and_a_promotion_is_applied(): void
+    {
+        $deprecation = null;
+        set_error_handler(static function (int $errno, string $errstr) use (&$deprecation): bool {
+            $deprecation = $errstr;
+
+            return true;
+        }, \E_USER_DEPRECATED);
+
+        try {
+            $provider = new UnitNetPriceProvider();
+        } finally {
+            restore_error_handler();
+        }
+
+        $unit = $this->createMock(OrderItemUnitInterface::class);
+        $orderItem = $this->createMock(OrderItemInterface::class);
+        $taxAdjustment = $this->createMock(AdjustmentInterface::class);
+
+        $unit->method('getOrderItem')->willReturn($orderItem);
+        $orderItem->method('getUnitPrice')->willReturn(12000);
+
+        $unit
+            ->method('getAdjustments')
+            ->with(AdjustmentInterface::TAX_ADJUSTMENT)
+            ->willReturn(new ArrayCollection([$taxAdjustment]));
+
+        // The neutral tax adjustment amount is calculated on the discounted (post-promotion)
+        // price, so subtracting getAmount() directly would diverge from the real net price.
+        // The tax must be recalculated on the full unit price instead.
+        $taxAdjustment->method('isNeutral')->willReturn(true);
+        $taxAdjustment->method('getDetails')->willReturn(['taxRateAmount' => 0.20]);
+
+        self::assertSame(10000, $provider->getUnitNetPrice($unit));
+    }
+
     #[Test]
     public function it_provides_net_price_for_unit_with_taxes_excluded_of_price(): void
     {