[FIX] point_of_sale: fix accounting entries

When a payment difference was created in the PoS, it was introducing
errors in the accounting entries.

Steps to reproduce:
-------------------
* Make sure bank payment method has an outstanding account
* Open PoS and make a sale paid by bank for 100$
* Close the session and introduce a payment difference of -10$
* Check the accounting entries created for the PoS session
> Observation: The difference is correctly recorded but the payment
  appears as a payment of 90$ instead of 100$.

Why the fix:
------------
We revert this fix (odoo#196253) that was
wrongly modifying the payment amount to fix the session report.

opw-4723227

closes odoo#219684

X-original-commit: d97cdc5
Signed-off-by: Adrien Guilliams (adgu) <adgu@odoo.com>
Signed-off-by: Robin Engels (roen) <roen@odoo.com>

Author: robinengels

addons/point_of_sale/models/pos_session.py

@@ -689,10 +689,10 @@ def _create_diff_account_move_for_split_payment_method(self, payment_method, dif
     def _get_diff_account_move_ref(self, payment_method):
         return _('Closing difference in %(payment_method)s (%(session)s)', payment_method=payment_method.name, session=self.name)
 
-    def _get_diff_vals(self, payment_method_id, diff_amount):
+    def _get_diff_vals(self, payment_method_id, diff_amount, outstanding_account=False):
         payment_method = self.env['pos.payment.method'].browse(payment_method_id)
         diff_compare_to_zero = self.currency_id.compare_amounts(diff_amount, 0)
-        source_account = payment_method.outstanding_account_id
+        source_account = payment_method.outstanding_account_id or outstanding_account
         destination_account = self.env['account.account']
 
         if (diff_compare_to_zero > 0):
@@ -1141,7 +1141,7 @@ def _create_combine_account_payment(self, payment_method, amounts, diff_amount):
         destination_account = self._get_receivable_account(payment_method)
 
         account_payment = self.env['account.payment'].with_context(pos_payment=True).create({
-            'amount': abs(amounts['amount']) + diff_amount,
+            'amount': abs(amounts['amount']),
             'journal_id': payment_method.journal_id.id,
             'force_outstanding_account_id': outstanding_account.id,
             'destination_account_id': destination_account.id,
@@ -1173,7 +1173,7 @@ def _create_combine_account_payment(self, payment_method, amounts, diff_amount):
         return account_payment.move_id.line_ids.filtered(lambda line: line.account_id == self._get_receivable_account(payment_method))
 
     def _apply_diff_on_account_payment_move(self, account_payment, payment_method, diff_amount):
-        diff_vals = self._get_diff_vals(payment_method.id, diff_amount)
+        diff_vals = self._get_diff_vals(payment_method.id, diff_amount, account_payment.outstanding_account_id)
         if not diff_vals:
             return
         source_vals, dest_vals = diff_vals
@@ -1190,6 +1190,9 @@ def _apply_diff_on_account_payment_move(self, account_payment, payment_method, d
                 })
             ]
         })
+        account_payment.write({
+            'amount': abs(new_balance),
+        })
         account_payment.move_id.action_post()
 
     def _create_split_account_payment(self, payment, amounts):

addons/point_of_sale/tests/test_point_of_sale_flow.py

@@ -2446,3 +2446,57 @@ def test_sum_only_pos_locations(self):
         self.assertEqual(len(result), 1, "Should return exactly one lot")
         self.assertEqual(result[0]['name'], 'TEST_LOT')
         self.assertEqual(result[0]['product_qty'], 15.0, "Should sum only quantities from POS source locations")
+
+    def test_payment_difference_accounting_items(self):
+        """Verify that the amount of the accounting items are correct when closing a session with a payment difference."""
+        self.product1 = self.env['product.product'].create({
+            'name': 'Test Product',
+            'lst_price': 100,
+        })
+        # Make a sale paid by bank
+        self.pos_config.open_ui()
+        session_id = self.pos_config.current_session_id
+        order = self.env['pos.order'].create({
+            'company_id': self.env.company.id,
+            'session_id': session_id.id,
+            'partner_id': False,
+            'lines': [Command.create({
+                'name': 'OL/0001',
+                'product_id': self.product1.id,
+                'price_unit': 100.00,
+                'discount': 0,
+                'qty': 1,
+                'tax_ids': False,
+                'price_subtotal': 100.00,
+                'price_subtotal_incl': 100.00,
+            })],
+            'pricelist_id': self.pos_config.pricelist_id.id,
+            'amount_paid': 100.00,
+            'amount_total': 100.00,
+            'amount_tax': 0.0,
+            'amount_return': 0.0,
+            'to_invoice': False,
+        })
+
+        # Make payment
+        payment_context = {"active_ids": order.ids, "active_id": order.id}
+        order_payment = self.env['pos.make.payment'].with_context(**payment_context).create({
+            'amount': order.amount_total,
+            'payment_method_id': self.bank_payment_method.id
+        })
+        order_payment.with_context(**payment_context).check()
+
+        session_id.action_pos_session_closing_control(bank_payment_method_diffs={self.bank_payment_method.id: -10.00})
+        self.bank_payment_move = session_id._get_related_account_moves().filtered(lambda move: 'Combine Bank' in move.ref)
+        self.assertRecordValues(self.bank_payment_move.line_ids.sorted('balance'), [{
+            'balance': -100.0,
+            'account_id': self.bank_payment_method.receivable_account_id.id,
+        },
+        {
+            'balance': 10.0,
+            'account_id': self.bank_payment_method.journal_id.loss_account_id.id,
+        },
+        {
+            'balance': 90.0,
+            'account_id': self.bank_payment_move.payment_ids.outstanding_account_id.id,
+        }])