[FIX] sale_loyalty: keep track of coupon changes on confirmed orders

Versions
--------
- 17.0+

Steps
-----
1. Have a coupon program;
2. add a 10% discount on order reward for 1 point;
3. add a 50% discount on order reward for 5 points;
4. generate a coupon with 10 points;
5. use coupon code on a confirmed order;
6. select 10% discount reward;
7. change to a 50% discount reward;
8. check coupon point total.

Issue
-----
Even though the 5 point reward was used, only 4 out of 10 points remain.

Cause
-----
When updating the reward line of a confirmed order, it keeps track of
point cost changes before & after a write. Its purpose is to restore
back the point difference on the coupon record.

The issue is that while point changes are stored, coupon changes are
not. When updating reward lines, `_reset_loyalty` is used, which removes
the `coupon_id` from the lines. As a consequence, attempting to restore
the point difference on `line.coupon_id` after an update, it writes to
an empty record.

Solution
--------
Store both coupons & their used points before write. After write,
restore the previous points to the previous coupon, and subtract the
current point cost from the current coupon. This way, any combination of
coupon/point changes should have the points updated as expected.

opw-4910922

closes odoo#231120

X-original-commit: ee7abc9
Signed-off-by: Levi Siuzdak <[email protected]>
Signed-off-by: Valeriya Chuprina (vchu) <[email protected]>

Author: lvsz

addons/sale_loyalty/models/sale_order_line.py

@@ -87,13 +87,16 @@ def create(self, vals_list):
     def write(self, vals):
         cost_in_vals = 'points_cost' in vals
         if cost_in_vals:
-            previous_cost = {l: l.points_cost for l in self}
+            previous_vals = {line: (line.points_cost, line.coupon_id) for line in self}
         res = super().write(vals)
         if cost_in_vals:
             # Update our coupon points if the order is in a confirmed state
-            for line in self:
-                if previous_cost[line] != line.points_cost and line.state == 'sale':
-                    line.coupon_id.points += (previous_cost[line] - line.points_cost)
+            for line, (previous_cost, previous_coupon) in previous_vals.items():
+                if line.state != 'sale':
+                    continue
+                if line.points_cost != previous_cost or line.coupon_id != previous_coupon:
+                    previous_coupon.points += previous_cost
+                    line.coupon_id.points -= line.points_cost
         return res
 
     def unlink(self):

addons/sale_loyalty/tests/test_program_with_code_operations.py

@@ -373,6 +373,49 @@ def test_public_partner_updated_in_next_order_coupon(self):
             "The coupon's partner_id should be updated if it was created for a Public User",
         )
 
+    def test_change_reward_on_confirmed_order(self):
+        """Check that changing rewards on a confirmed order restores points on the coupon.
+        Tested flow:
+            - have a coupon program with 2 discount rewards;
+            - have confirmed order;
+            - apply a 10% discount reward, costing 1 point;
+            - change to a 50% discount reward, costing 5 points;
+            - check that there are still 5 points left on the coupon.
+        """
+        program = self.code_promotion_program_with_discount
+        program.update({
+            'rule_ids': [Command.clear()],
+            'reward_ids': [Command.create({
+                'discount': 50,
+                'discount_mode': 'percent',
+                'discount_applicability': 'order',
+                'required_points': 5,
+            })],
+        })
+        discount10, discount50 = program.reward_ids
+
+        self.env['loyalty.generate.wizard'].with_context(active_id=program.id).create({
+            'coupon_qty': 1,
+            'points_granted': 10,
+        }).generate_coupons()
+        coupon = program.coupon_ids
+
+        order = self.empty_order
+        order.order_line = [Command.create({'product_id': self.product_C.id})]
+        order.action_confirm()
+
+        order.order_line.product_updatable = True  # in case `sale_project` is installed
+        order._apply_program_reward(discount10, coupon)
+        reward_line = order.order_line.filtered('is_reward_line')
+        self.assertEqual(order.amount_total, 90, "10% discount should be applied")
+        self.assertEqual(coupon.points, 9, "10% discount reward should use 1 point")
+
+        order.order_line.product_updatable = True  # in case `sale_project` is installed
+        order._apply_program_reward(discount50, coupon)
+        self.assertIn(reward_line, order.order_line, "Reward line should be re-used")
+        self.assertEqual(order.amount_total, 50, "50% discount should be applied")
+        self.assertEqual(coupon.points, 5, "50% discount reward should use 5 points")
+
     def test_edit_and_reapply_promotion_program(self):
         # The flow:
         # 1. Create a program auto applied, giving a fixed amount discount