[FIX] account: reconcile over-amount bank statements in foreign currencies

When a bank statement reconciles its lines with payment using a foreign currency,
there is a mix up of values between the currency set in bank statement and payment against the company currency.

Current Behavior

Company Currency: MXN
Bank Statement Currency: USD
Payment Currency: USD
Current Rate 0.05130836

1) Generate a bank statement with 990 USD.
2) Generate a payment with 1000 USD.
3) Reconcile the bank statement against the payment.

The reconcile process generates a payment with the difference (10 USD)
Before this commit, this automatically created payment took an erroneous amount,
Taking a currency-converted amount where it should not have

It was happening because the reconcile process uses the debit or credit value(Local Currency)
against bank statement line amount (Foreign Currency).

After this commit, the amount set in the generated payment because of the difference is 10 USD.

closed odoo#30623

closes odoo/odoo#30779

addons/account/models/account_bank_statement.py

@@ -557,8 +557,11 @@ class AccountBankStatementLine(models.Model):
 
         # Fully reconciled moves are just linked to the bank statement
         total = self.amount
+        currency = self.currency_id or statement_currency
         for aml_rec in payment_aml_rec:
-            total -= aml_rec.debit - aml_rec.credit
+            balance = aml_rec.amount_currency if aml_rec.currency_id else aml_rec.balance
+            aml_currency = aml_rec.currency_id or aml_rec.company_currency_id
+            total -= aml_currency._convert(balance, currency, aml_rec.company_id, aml_rec.date)
             aml_rec.with_context(check_move_validity=False).write({'statement_line_id': self.id})
             counterpart_moves = (counterpart_moves | aml_rec.move_id)
             if aml_rec.journal_id.post_at_bank_rec and aml_rec.payment_id and aml_rec.move_id.state == 'draft':

addons/account/tests/test_reconciliation.py

@@ -529,6 +529,14 @@ class TestReconciliation(AccountingTestCase):
             self.diff_income_account.id: {'debit': 0.0, 'credit': 3.27, 'amount_currency': -5, 'currency_id': self.currency_usd_id},
             self.account_rcv.id: {'debit': 0.0, 'credit': 52.33, 'amount_currency': -80, 'currency_id': self.currency_usd_id},
         }
+
+        payments = bank_stmt_aml.mapped('payment_id')
+        # creation and reconciliation of the over-amount statement
+        # has created an another payment
+        self.assertEqual(len(payments), 2)
+        # Check amount of second, automatically created payment
+        self.assertEqual((payments - payment).amount, 5)
+
         for aml in bank_stmt_aml:
             line = lines[aml.account_id.id]
             if type(line) == list: