Only create carts once a product is added

Previously, every page visit created a cart. This was very inefficient
and lead to huge tables on high-traffic websites. Carts are now only
created once they are actually saved, for example when a product is
added.

Fixes #280, #1064

classes/traits/ShippingMethods.php

@@ -16,7 +16,9 @@ public function getAvailableShippingMethods()
     public function setShippingMethod(?ShippingMethod $method)
     {
         $this->shipping_method_id = $method ? $method->id : null;
-        $this->save();
+        if ($this->exists) {
+            $this->save();
+        }
     }
 
     /**

classes/traits/cart/CartSession.php

@@ -18,7 +18,7 @@ public static function byUser(?User $user)
         }
 
         $cart = self::orderBy('created_at', 'DESC')
-                    ->firstOrCreate(['customer_id' => $user->customer->id]);
+                    ->firstOrNew(['customer_id' => $user->customer->id]);
 
         if ( ! $cart->shipping_address_id || ! $cart->billing_address_id) {
             if ( ! $cart->shipping_address_id) {
@@ -27,7 +27,9 @@ public static function byUser(?User $user)
             if ( ! $cart->billing_address_id) {
                 $cart->billing_address_id = $user->customer->default_billing_address_id;
             }
-            $cart->save();
+            if ($cart->exists) {
+                $cart->save();
+            }
         }
 
         return $cart;
@@ -47,7 +49,7 @@ protected static function bySession(): Cart
         Cookie::queue('cart_session_id', $sessionId, 9e6);
         Session::put('cart_session_id', $sessionId);
 
-        return self::orderBy('created_at', 'DESC')->firstOrCreate(['session_id' => $sessionId]);
+        return self::orderBy('created_at', 'DESC')->firstOrNew(['session_id' => $sessionId]);
     }
 
     /**

updates/version.yaml

@@ -590,3 +590,5 @@ v3.4.1:
     - 'Prevent from adding too many queue jobs for UniquePropertyValue'
 v3.4.2:
     - 'Fixed demo seeder with new users plugin'
+v3.4.3:
+    - 'Only create carts once a product is added'