Count negative inventory values as out of stock (#307)

Signed-off-by: Philipp Daun <post@philippdaun.net>

Author: daun

src/Tags/Shopify.php

@@ -284,7 +284,7 @@ protected function isInStock($variants): bool
             }
         }
 
-        if ($stock === 0 and $deny) {
+        if ($stock <= 0 and $deny) {
             return false;
         }
 

tests/Unit/TagsTest.php

@@ -156,6 +156,18 @@ public function outputs_in_stock()
         ])->save();
 
         $this->assertEquals('', $this->tag('{{ if {shopify:in_stock} }}Yes{{ /if }}', ['slug' => 'obi-wan']));
+
+        $variant->merge([
+            'inventory_quantity' => -1,
+        ])->save();
+
+        $this->assertEquals('', $this->tag('{{ if {shopify:in_stock} }}Yes{{ /if }}', ['slug' => 'obi-wan']));
+
+        $variant->merge([
+            'inventory_quantity' => null,
+        ])->save();
+
+        $this->assertEquals('', $this->tag('{{ if {shopify:in_stock} }}Yes{{ /if }}', ['slug' => 'obi-wan']));
     }
 
     #[Test]