[6.x] Fix error with {{ sc:cart:raw_tax_total_split }} tag (#1037)

* Add failing test

* Refactor `raw_tax_total_split` tag to avoid getting data post-augmentation

Author: duncanmcclean

src/Tags/CartTags.php

@@ -160,16 +160,16 @@ public function taxTotalSplit(): Collection
 
     public function rawTaxTotalSplit(): Collection
     {
-        return collect($this->items())
-            ->groupBy(function ($item) {
-                return $item['tax']['rate'];
-            })
-            ->map(function ($group, $groupRate) {
+        if (! $this->hasCart()) {
+            return collect();
+        }
+
+        return $this->getCart()->lineItems()
+            ->groupBy(fn ($lineItem) => $lineItem->tax()['rate'])
+            ->map(function ($group, $rate) {
                 return [
-                    'rate' => $groupRate,
-                    'amount' => $group->sum(function ($item) {
-                        return $item['tax']['amount'];
-                    }),
+                    'rate' => $rate,
+                    'amount' => $group->sum(fn ($lineItem) => $lineItem->tax()['amount']),
                 ];
             })
             ->values();

tests/Tags/CartTagTest.php

@@ -429,6 +429,12 @@
     $taxReduced = $cartProduct3->tax()['amount'];
     $taxReducedFormatted = Currency::parse($taxReduced, Site::default());
 
+    // Expected tag output format = '19:1234|7:5678'
+    $renderedTag = (string) tag('{{ sc:cart:rawTaxTotalSplit }}{{ rate }}:{{ amount }}|{{ /sc:cart:rawTaxTotalSplit }}');
+
+    expect($renderedTag)->toContain($taxRateDefault->rate().':'.$taxDefault);
+    expect($renderedTag)->toContain($taxRateReduced->rate().':'.$taxReduced);
+
     // Expected tag output format = '7:£12.34|19:£56.78'
     $renderedTag = (string) tag('{{ sc:cart:taxTotalSplit }}{{ rate }}:{{ amount }}|{{ /sc:cart:taxTotalSplit }}');