From 30a35c50de0b143c22fe3501f721a3291660b304 Mon Sep 17 00:00:00 2001
From: Michel Bade <m.bade@shopware.com>
Date: Mon, 21 Sep 2026 09:19:13 +0200
Subject: [PATCH] fix: wrong tax summing

---
 src/Context/Cart/CalculatedTax.php       | 14 ++---
 tests/Context/Cart/CalculatedTaxTest.php | 69 ++++++++++++++++++++++++
 2 files changed, 77 insertions(+), 6 deletions(-)

diff --git a/src/Context/Cart/CalculatedTax.php b/src/Context/Cart/CalculatedTax.php
index e8410d3..0788f7c 100644
--- a/src/Context/Cart/CalculatedTax.php
+++ b/src/Context/Cart/CalculatedTax.php
@@ -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,
             ]);
         }
 
diff --git a/tests/Context/Cart/CalculatedTaxTest.php b/tests/Context/Cart/CalculatedTaxTest.php
index 74d6644..8f5e65c 100644
--- a/tests/Context/Cart/CalculatedTaxTest.php
+++ b/tests/Context/Cart/CalculatedTaxTest.php
@@ -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());
+    }
 }