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fix: wrong tax summing #70

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Merged
Lennart Tinkloh (lernhart) merged 1 commit into from
Sep 21, 2026
Merged

fix: wrong tax summing #70

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14 changes: 8 additions & 6 deletions src/Context/Cart/CalculatedTax.php
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Original file line number Diff line number Diff line change
Expand Up @@ -42,18 +42,20 @@ public static function sum(Collection $calculatedTaxes): Collection
$new = [];

foreach ($calculatedTaxes as $calculatedTax) {
$exists = isset($new[$calculatedTax->getTaxRate()]);
$key = (string) $calculatedTax->getTaxRate();

$exists = isset($new[$key]);
if (!$exists) {
$new[$calculatedTax->getTaxRate()] = $calculatedTax;
$new[$key] = $calculatedTax;

continue;
}

$new[$calculatedTax->getTaxRate()] = new CalculatedTax([
$new[$key] = new CalculatedTax([
'taxRate' => $calculatedTax->getTaxRate(),
'price' => $new[$calculatedTax->getTaxRate()]->getPrice() + $calculatedTax->getPrice(),
'tax' => $new[$calculatedTax->getTaxRate()]->getTax() + $calculatedTax->getTax(),
'label' => implode(' + ', array_filter([$new[$calculatedTax->getTaxRate()]->getLabel(), $calculatedTax->getLabel()])) ?: null,
'price' => $new[$key]->getPrice() + $calculatedTax->getPrice(),
'tax' => $new[$key]->getTax() + $calculatedTax->getTax(),
'label' => implode(' + ', array_filter([$new[$key]->getLabel(), $calculatedTax->getLabel()])) ?: null,
]);
}

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69 changes: 69 additions & 0 deletions tests/Context/Cart/CalculatedTaxTest.php
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Original file line number Diff line number Diff line change
Expand Up @@ -66,4 +66,73 @@ public function testSum(): void
static::assertSame(0.7, $tax7->getTax());
static::assertNull($tax7->getLabel());
}

/**
* Tax rates are grouped by a string key. A float key would be truncated to an int
* by PHP, so 7.0 and 7.7 would collide and be summed into a single wrong rate.
*/
public function testSumKeepsTaxRatesWithTheSameIntegerPartApart(): void
{
$calculatedTaxes = new Collection([
new CalculatedTax([
'taxRate' => 7.0,
'price' => 10.0,
'tax' => 0.7,
'label' => 'reduced',
]),
new CalculatedTax([
'taxRate' => 7.7,
'price' => 20.0,
'tax' => 1.54,
'label' => 'standard',
]),
]);

$sum = CalculatedTax::sum($calculatedTaxes);

static::assertCount(2, $sum);

$tax7 = $sum->get('7');
static::assertNotNull($tax7);
static::assertSame(7.0, $tax7->getTaxRate());
static::assertSame(10.0, $tax7->getPrice());
static::assertSame(0.7, $tax7->getTax());
static::assertSame('reduced', $tax7->getLabel());

$tax77 = $sum->get('7.7');
static::assertNotNull($tax77);
static::assertSame(7.7, $tax77->getTaxRate());
static::assertSame(20.0, $tax77->getPrice());
static::assertSame(1.54, $tax77->getTax());
static::assertSame('standard', $tax77->getLabel());
}

public function testSumMergesIdenticalFractionalTaxRates(): void
{
$calculatedTaxes = new Collection([
new CalculatedTax([
'taxRate' => 7.7,
'price' => 10.0,
'tax' => 0.77,
'label' => 'label 1',
]),
new CalculatedTax([
'taxRate' => 7.7,
'price' => 20.0,
'tax' => 1.54,
'label' => 'label 2',
]),
]);

$sum = CalculatedTax::sum($calculatedTaxes);

static::assertCount(1, $sum);

$tax77 = $sum->get('7.7');
static::assertNotNull($tax77);
static::assertSame(7.7, $tax77->getTaxRate());
static::assertSame(30.0, $tax77->getPrice());
static::assertSame(2.31, $tax77->getTax());
static::assertSame('label 1 + label 2', $tax77->getLabel());
}
}
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