[FIX] delivery: delivery line is not set to zero cost

If the chosen delivery method has free_over active, and if the cost
of the sale over exceeds the free_over amount, the delivery line
should have price_unit of zero.

addons/delivery/models/sale_order.py

@@ -106,7 +106,7 @@ class SaleOrder(models.Model):
             values['name'] += _(' (Estimated Cost: %s )') % self._format_currency_amount(price_unit)
         else:
             values['price_unit'] = price_unit
-        if carrier.free_over and self._compute_amount_total_without_delivery() >= price_unit:
+        if carrier.free_over and self.currency_id.is_zero(price_unit) :
             values['name'] += '\n' + 'Free Shipping'
         if self.order_line:
             values['sequence'] = self.order_line[-1].sequence + 1

addons/delivery/wizard/choose_delivery_carrier.py

@@ -19,7 +19,7 @@ class ChooseDeliveryCarrier(models.TransientModel):
     )
     delivery_type = fields.Selection(related='carrier_id.delivery_type')
     delivery_price = fields.Float()
-    display_price = fields.Float(string='Cost')
+    display_price = fields.Float(string='Cost', readonly=True)
     currency_id = fields.Many2one('res.currency', related='order_id.currency_id')
     company_id = fields.Many2one('res.company', related='order_id.company_id')
     available_carrier_ids = fields.Many2many("delivery.carrier", compute='_compute_available_carrier', string="Available Carriers")
@@ -88,7 +88,7 @@ class ChooseDeliveryCarrier(models.TransientModel):
         }
 
     def button_confirm(self):
-        self.order_id.set_delivery_line(self.carrier_id, self.display_price)
+        self.order_id.set_delivery_line(self.carrier_id, self.delivery_price)
         self.order_id.write({
             'recompute_delivery_price': False,
             'delivery_message': self.delivery_message,