[FIX] loyalty: add link to discout products in loyalty.program form view

A customer has a gift card product linked to a specific income account.
When sold, the income account associated with the gift card product is
credited correctly. The issue arises when the gift card is consumed
within a sales order. An order line is added using a "dummy product" to
indicate the gift card's usage (one dummy product is created for each
loyalty program). Due to this, when an account move is created from the
sale order, the income account defined on the dummy product is used
instead of the one on the gift card product. This leads to the wrong
income account being debited, causing unbalanced accounting entries.

There's currently no way to link back to the original gift card product
from a `loyalty.card` record. Because of this, the system cannot
identify the correct income account to debit. Fixing this would require
adding a new field, which we can't do in stable.

A potential workaround is to find the dummy product and set the income
account to the same as the gift card product. However, with one dummy
product for each `loyalty.program`, all named "Gift Card", finding the
right dummy product is difficult.

This commit aims to simplify the workaround by adding a link to the
associated dummy product on the `loyalty.program` form view. This change
should ease the process of finding and modifying the correct dummy
product, thus mitigating the issue in the current stable version.

opw-3239720
opw-3373287

closes odoo/odoo#133461

X-original-commit: 767eccb122055cd9a474ce5110cb7296eb9ef4c2
Signed-off-by: Séna Serge Nshimiyimana (sesn) <sesn@odoo.com>

addons/loyalty/i18n/loyalty.pot

@@ -1419,6 +1419,11 @@ msgstr ""
 msgid "Product Variant"
 msgstr ""
 
+#. module: loyalty
+#: model:ir.model.fields,help:loyalty.field_loyalty_program__discount_product_id
+msgid "Product used in the sales order to apply the discount."
+msgstr ""
+
 #. module: loyalty
 #: model:ir.model.fields,help:loyalty.field_loyalty_reward__discount_line_product_id
 msgid ""

addons/loyalty/models/loyalty_program.py

@@ -91,6 +91,14 @@ class LoyaltyProgram(models.Model):
     is_nominative = fields.Boolean(compute='_compute_is_nominative')
     is_payment_program = fields.Boolean(compute='_compute_is_payment_program')
 
+    payment_program_discount_product_id = fields.Many2one(
+        'product.product',
+        string='Discount Product',
+        compute='_compute_payment_program_discount_product_id',
+        readonly=True,
+        help="Product used in the sales order to apply the discount."
+    )
+
     # Technical field used for a label
     available_on = fields.Boolean("Available On", store=False,
         help="""
@@ -183,6 +191,14 @@ class LoyaltyProgram(models.Model):
         for program in self:
             program.is_payment_program = program.program_type in ('gift_card', 'ewallet')
 
+    @api.depends('reward_ids.discount_line_product_id')
+    def _compute_payment_program_discount_product_id(self):
+        for program in self:
+            if program.is_payment_program:
+                program.payment_program_discount_product_id = program.reward_ids[0].discount_line_product_id
+            else:
+                program.payment_program_discount_product_id = False
+
     @api.model
     def _program_items_name(self):
         return {

addons/loyalty/views/loyalty_program_views.xml

@@ -82,6 +82,7 @@
                             </div>
                             <field name="trigger_product_ids" string="Gift Card Products" widget="many2many_tags" invisible="program_type != 'gift_card'"/>
                             <field name="trigger_product_ids" string="eWallet Products" widget="many2many_tags" invisible="program_type != 'ewallet'"/>
+                            <field name="payment_program_discount_product_id" groups="base.group_no_one" invisible="program_type not in ('gift_card', 'ewallet')"/>
                             <field name="mail_template_id" invisible="program_type not in ('gift_card', 'ewallet')"/>
                             <field name="currency_id"/>
                             <field name="currency_symbol" invisible="1"/>

addons/loyalty/views/loyalty_reward_views.xml

@@ -55,6 +55,7 @@
                     </group>
                     <group>
                         <field name="description" string="Description on order"/>
+                        <field name="discount_line_product_id" string="Discount product" groups="base.group_no_one"/>
                     </group>
                 </sheet>
             </form>