[FIX] website_sale: Display pricelist price if no price_unit

Steps to reproduce:

  - Install website_sale module
  - Enable discount and advanced pricelist in settings
  - Create product with sale price 0$ and set a website in
  - eCommerce + publish the product
  - Create pricelist PPP with Discount Policy as
  - "Show public price & discount to the customer" and selectable in the website
  - Go to the product and set an extra price of 10$ for the new pricelist
  - Go to the product in the eshop and select the pricelist PPP
  - Add the product to the shop cart

Issue:

  The price displayed is 0$ instead of 10$.

Cause:

  Since price_unit equal 0$, not possible to calculate the discount and
  therefore using the 0$ value.

Solution:

  Use price of pricelist in case 'discount_policy' is 'without_discount'
  and price_unit equal 0$.

opw-2652192
Forward-Port-Of: #78570

Cherry pick of 32d34ffb04b3c6a8397c8ff7eb4e8a3dd9fb8a95

closes odoo/odoo#78701

Signed-off-by: bon-odoo <nboulif@users.noreply.github.com>

addons/website_sale/models/sale_order.py

@@ -125,6 +125,10 @@ class SaleOrder(models.Model):
                     # but we still want to use the price defined on the pricelist
                     discount = 0
                     pu = price
+            else:
+                # In case the price_unit equal 0 and therefore not able to calculate the discount,
+                # we fallback on the price defined on the pricelist.
+                pu = price
         else:
             pu = product.price
             if order.pricelist_id and order.partner_id:

addons/website_sale/tests/test_website_sale_pricelist.py

@@ -241,6 +241,44 @@ class TestWebsitePriceList(TransactionCase):
         self.assertEqual(sol.price_reduce, 27.75, 'Both reductions should be applied')
         self.assertEqual(sol.price_total, 13875)
 
+    def test_pricelist_with_no_list_price(self):
+        product = self.env['product.product'].create({
+            'name': 'Super Product',
+            'list_price': 0,
+            'taxes_id': False,
+        })
+        current_website = self.env['website'].get_current_website()
+        website_pricelist = current_website.get_current_pricelist()
+        website_pricelist.write({
+            'discount_policy': 'without_discount',
+            'item_ids': [(5, 0, 0), (0, 0, {
+                'applied_on': '1_product',
+                'product_tmpl_id': product.product_tmpl_id.id,
+                'min_quantity': 0,
+                'compute_price': 'fixed',
+                'fixed_price': 10,
+            })]
+        })
+        so = self.env['sale.order'].create({
+            'partner_id': self.env.user.partner_id.id,
+            'order_line': [(0, 0, {
+                'name': product.name,
+                'product_id': product.id,
+                'product_uom_qty': 5,
+                'product_uom': product.uom_id.id,
+                'price_unit': product.list_price,
+                'tax_id': False,
+            })]
+        })
+        sol = so.order_line
+        self.assertEqual(sol.price_total, 0)
+        so.pricelist_id = website_pricelist
+        with MockRequest(self.env, website=current_website, sale_order_id=so.id):
+            so._cart_update(product_id=product.id, line_id=sol.id, set_qty=5)
+        self.assertEqual(sol.price_unit, 10.0, 'Pricelist price should be applied')
+        self.assertEqual(sol.price_reduce, 10.0, 'Pricelist price should be applied')
+        self.assertEqual(sol.price_total, 50.0)
+
 
 def simulate_frontend_context(self, website_id=1):
     # Mock this method will be enough to simulate frontend context in most methods