[FIX] website_sale: do not create zero-quantity lines

We do not want to allow the creation of lines with zero quantity,
Although we do not know of a standard flow making such requests,
the cart_update routes could accept information such as
* {"product_id": X, "set_qty":0}
* {"product_id": X, "add_qty":0}

If a line with product X already exists, it'll be deleted.
If no such line exists, a new one would be created, which is not
something we want to support.

closes odoo/odoo#118999

X-original-commit: 231c8aa79ddd0b1f4ed47508fa22596ac19daacb
Signed-off-by: Victor Feyens (vfe) <vfe@odoo.com>
Co-authored-by: Paul Morelle <pmo@odoo.com>

addons/website_sale/models/sale_order.py

@@ -132,7 +132,7 @@ class SaleOrder(models.Model):
             update_values = self._prepare_order_line_update_values(order_line, quantity, **kwargs)
             if update_values:
                 self._update_cart_line_values(order_line, update_values)
-        elif quantity >= 0:
+        elif quantity > 0:
             # Create new line
             order_line_values = self._prepare_order_line_values(product_id, quantity, **kwargs)
             order_line = self.env['sale.order.line'].sudo().create(order_line_values)

addons/website_sale/tests/test_website_sale_cart.py

@@ -78,3 +78,35 @@ class WebsiteSaleCart(TransactionCase):
             # Try processing payment with the old amount
             with self.assertRaises(UserError):
                 PaymentPortal().shop_payment_transaction(sale_order.id, sale_order.access_token, amount=old_amount)
+
+    def test_update_cart_zero_qty(self):
+        # Try to remove a product that has already been removed
+        product = self.env['product.product'].create({
+            'name': 'Test Product',
+            'sale_ok': True,
+            'website_published': True,
+            'lst_price': 1000.0,
+            'standard_price': 800.0,
+        })
+        portal_user = self.env.ref('base.demo_user0')
+        website = self.website.with_user(portal_user)
+
+        SaleOrderLine = self.env['sale.order.line']
+
+        with MockRequest(product.with_user(portal_user).env, website=website):
+            # add the product to the cart
+            self.WebsiteSaleController.cart_update_json(product_id=product.id, add_qty=1)
+            sale_order = website.sale_get_order()
+            self.assertEqual(sale_order.amount_total, 1150.0)
+
+            # remove the product from the cart
+            self.WebsiteSaleController.cart_update_json(product_id=product.id, line_id=sale_order.order_line.id, set_qty=0)
+            self.assertEqual(sale_order.amount_total, 0.0)
+            self.assertEqual(sale_order.order_line, SaleOrderLine)
+
+            # removing the product again doesn't add a line with zero quantity
+            self.WebsiteSaleController.cart_update_json(product_id=product.id, set_qty=0)
+            self.assertEqual(sale_order.order_line, SaleOrderLine)
+
+            self.WebsiteSaleController.cart_update_json(product_id=product.id, add_qty=0)
+            self.assertEqual(sale_order.order_line, SaleOrderLine)