Tax zones leading to bad tax calculation

[jacquesbh]

Sylius version affected: all since we have the tax zones I think

Description
Considering a country (let's say FRANCE) is in two zones (let's say ZONE A and then ZONE B, both type "country" so same priority, but A entered before B in database).
Considering a tax rate for ZONE A.

If I order with a billing address in FRANCE, then I don't get the tax, but I should because FRANCE is in ZONE A.

BUT !

Sylius/src/Sylius/Component/Addressing/Matcher/ZoneMatcher.php

Lines 41 to 59 in 7bdc5d4

	public function match(AddressInterface $address, ?string $scope = null): ?ZoneInterface
	{
	$zones = [];
	/** @var ZoneInterface $zone */
	foreach ($this->getZones($scope) as $zone) {
	if ($this->addressBelongsToZone($address, $zone)) {
	$zones[$zone->getType()] = $zone;
	}
	}
	foreach (self::PRIORITIES as $priority) {
	if (isset($zones[$priority])) {
	return $zones[$priority];
	}
	}
	return null;
	}

Here we take the last zone in the loop (line 46), which will lead to ZONE B.

And since ZONE B ≠ ZONE A (zone with the tax applied) then I won't have any tax applied.

The issue here is: we consider a country to be in ONE zone, but it can be in more than one zone.

Steps to reproduce

Add the ZONE A and ZONE B for the following countries: FRANCE. Add them in this order so ZONE B is the last one taken into account in the ZoneMatcher.
Add a tax rate applying on ZONE A.
Order something with FRANCE as billing country.
You won't have any tax, but you SHOULD.

Possible Solution

I think it's important to consider that a country can be in more than one zone and to compare all zones to the tax rates, instead of only one.

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed in a week if no further activity occurs. Thank you for your contributions.

[jacquesbh]

Do not stale.

This is still an issue, and can till lead to some errors in taxes.

[jacquesbh]

Applying more than one tax will lead to more issues.
Like if we have 2 taxes included in price: what is the excluding price of the product? :p

Also having more than one zone in the match fixes the issue we have.

I think adding a priority to the Tax rates could help fixe the side effect of the first fix.

So, what I suggest:

• Always use a matchAll to match zones.
• Add a priority on Tax rates and then we apply only one tax per item (product, shipping)

@Sylius/core-team We need to discuss this, there is a big issue here and I am very surprised than nobody complained about it.

[jacquesbh]

Or we can say that an item (product or shipping) can have only one "tax included in the price" applied.

[maximehuran]

The snippet above correct the missing zones tax application but we can have some weird cases.
If 2 taxes are included in price, the calculation is not correct.
I think it could be great to have only one tax included in price applied, and the other (not included in price) can be applied too.

diff --git a/src/Sylius/Component/Core/OrderProcessing/OrderTaxesProcessor.php b/src/Sylius/Component/Core/OrderProcessing/OrderTaxesProcessor.php
index a39978abb4..52147c925e 100644
--- a/src/Sylius/Component/Core/OrderProcessing/OrderTaxesProcessor.php
+++ b/src/Sylius/Component/Core/OrderProcessing/OrderTaxesProcessor.php
@@ -58,34 +58,40 @@ final class OrderTaxesProcessor implements OrderProcessorInterface
             return;
         }
 
-        $zone = $this->getTaxZone($order);
+        $zones = $this->getTaxZones($order);
 
-        if (null === $zone) {
+        if (null === $zones) {
             return;
         }
 
+        $strategyApplied = false;
         /** @var TaxCalculationStrategyInterface $strategy */
         foreach ($this->strategyRegistry->all() as $strategy) {
-            if ($strategy->supports($order, $zone)) {
-                $strategy->applyTaxes($order, $zone);
-
-                return;
+            foreach ($zones as $zone) {
+                if ($strategy->supports($order, $zone)) {
+                    $strategy->applyTaxes($order, $zone);
+                    $strategyApplied = true;
+                }
             }
         }
 
-        throw new UnsupportedTaxCalculationStrategyException();
+        if (!$strategyApplied) {
+            throw new UnsupportedTaxCalculationStrategyException();
+        }
     }
 
-    private function getTaxZone(OrderInterface $order): ?ZoneInterface
+    private function getTaxZones(OrderInterface $order): ?array
     {
         $billingAddress = $order->getBillingAddress();
-        $zone = null;
+        $zones = null;
 
         if (null !== $billingAddress) {
-            $zone = $this->zoneMatcher->match($billingAddress, Scope::TAX);
+            $zones = $this->zoneMatcher->matchAll($billingAddress, Scope::TAX);
         }
 
-        return $zone ?: $this->defaultTaxZoneProvider->getZone($order);
+        $defaultTaxZone = $this->defaultTaxZoneProvider->getZone($order);
+
+        return $zones ?: ($defaultTaxZone ? [$defaultTaxZone] : null) ;
     }
 
     private function clearTaxes(OrderInterface $order): void