[FIX] account: Fix statement line rounding issue multi-currency

When reconciling a statement line with multiple lines in a multi-currency environment, it could lead to a rounding issue due to the currency rates. It could lead to an auto-generated open-balance of 0.01 amount to auto-balance the journal entry but the result is wrong since the partner has an open amount left on the receivable/payable account.

closes odoo/odoo#64620

Signed-off-by: oco-odoo <oco-odoo@users.noreply.github.com>

2 files changed, 72 insertions, 2 deletions

diff --git a/addons/account/models/account_bank_statement.py b/addons/account/models/account_bank_statement.py
index 5a3593ccf9a..805cc6b7e31 100644
--- a/addons/account/models/account_bank_statement.py
+++ b/addons/account/models/account_bank_statement.py
@@ -1024,6 +1024,9 @@ class AccountBankStatementLine(models.Model):
         '''
 
         self.ensure_one()
+        journal = self.journal_id
+        company_currency = journal.company_id.currency_id
+        foreign_currency = self.foreign_currency_id or journal.currency_id or company_currency
 
         liquidity_lines, suspense_lines, other_lines = self._seek_for_lines()
 
@@ -1040,6 +1043,7 @@ class AccountBankStatementLine(models.Model):
         reconciliation_overview = []
 
         total_balance = liquidity_lines.balance
+        total_amount_currency = liquidity_lines.amount_currency
 
         # Step 1: Split 'lines_vals_list' into two batches:
         # - The existing account.move.lines that need to be reconciled with the statement line.
@@ -1061,6 +1065,7 @@ class AccountBankStatementLine(models.Model):
                 # Newly created account.move.line from scratch.
                 line_vals = self._prepare_counterpart_move_line_vals(vals)
                 total_balance += line_vals['debit'] - line_vals['credit']
+                total_amount_currency += line_vals['amount_currency']
 
                 reconciliation_overview.append({
                     'line_vals': line_vals,
@@ -1072,6 +1077,7 @@ class AccountBankStatementLine(models.Model):
         for line, counterpart_vals in zip(existing_lines, to_process_vals):
             line_vals = self._prepare_counterpart_move_line_vals(counterpart_vals, move_line=line)
             balance = line_vals['debit'] - line_vals['credit']
+            amount_currency = line_vals['amount_currency']
 
             reconciliation_vals = {
                 'line_vals': line_vals,
@@ -1084,7 +1090,7 @@ class AccountBankStatementLine(models.Model):
                 payment_vals = self.env['account.payment.register']\
                     .with_context(active_model='account.move.line', active_ids=line.ids)\
                     .create({
-                        'amount': abs(line_vals['amount_currency']) if line_vals['currency_id'] else abs(balance),
+                        'amount': abs(amount_currency) if line_vals['currency_id'] else abs(balance),
                         'payment_date': self.date,
                         'payment_type': 'inbound' if balance < 0.0 else 'outbound',
                         'journal_id': self.journal_id.id,
@@ -1127,8 +1133,21 @@ class AccountBankStatementLine(models.Model):
             reconciliation_overview.append(reconciliation_vals)
 
             total_balance += balance
+            total_amount_currency += amount_currency
+
+        # Step 3: Fix rounding issue due to currency conversions.
+        # Add the remaining balance on the first encountered line starting with the custom ones.
+
+        if foreign_currency.is_zero(total_amount_currency) and not company_currency.is_zero(total_balance):
+            vals = reconciliation_overview[0]['line_vals']
+            new_balance = vals['debit'] - vals['credit'] - total_balance
+            vals.update({
+                'debit': new_balance if new_balance > 0.0 else 0.0,
+                'credit': -new_balance if new_balance < 0.0 else 0.0,
+            })
+            total_balance = 0.0
 
-        # Step 3: If the journal entry is not yet balanced, create an open balance.
+        # Step 4: If the journal entry is not yet balanced, create an open balance.
 
         if self.company_currency_id.round(total_balance):
             counterpart_vals = {
diff --git a/addons/account/tests/test_account_bank_statement.py b/addons/account/tests/test_account_bank_statement.py
index 253c9e8243e..c582a6d1dc3 100644
--- a/addons/account/tests/test_account_bank_statement.py
+++ b/addons/account/tests/test_account_bank_statement.py
@@ -1498,3 +1498,54 @@ class TestAccountBankStatementLine(TestAccountBankStatementCommon):
                 'amount_residual_currency': 0.0,
             },
         ])
+
+    def test_conversion_rate_rounding_issue(self):
+        ''' Ensure the reconciliation is well handling the rounding issue due to multiple currency conversion rates.
+
+        In this test, the resulting journal entry after reconciliation is:
+        {'amount_currency': 7541.66,    'debit': 6446.97,   'credit': 0.0}
+        {'amount_currency': 226.04,     'debit': 193.22,    'credit': 0.0}
+        {'amount_currency': -7767.70,   'debit': 0.0,       'credit': 6640.19}
+        ... but 226.04 / 1.1698 = 193.23. In this situation, 0.01 has been removed from this write-off line in order to
+        avoid an unecessary open-balance line being an exchange difference issue.
+        '''
+        self.bank_journal_2.currency_id = self.currency_2
+        self.currency_data['rates'][-1].rate = 1.1698
+
+        statement = self.env['account.bank.statement'].create({
+            'name': 'test_statement',
+            'date': '2017-01-01',
+            'journal_id': self.bank_journal_2.id,
+            'line_ids': [
+                (0, 0, {
+                    'date': '2019-01-01',
+                    'payment_ref': 'line_1',
+                    'partner_id': self.partner_a.id,
+                    'amount': 7541.66,
+                }),
+            ],
+        })
+        statement.button_post()
+        statement_line = statement.line_ids
+
+        payment = self.env['account.payment'].create({
+            'amount': 7767.70,
+            'date': '2019-01-01',
+            'currency_id': self.currency_2.id,
+            'payment_type': 'inbound',
+            'partner_type': 'customer',
+        })
+        payment.action_post()
+        liquidity_lines, counterpart_lines, writeoff_lines = payment._seek_for_lines()
+        self.assertRecordValues(liquidity_lines, [{'amount_currency': 7767.70}])
+
+        statement_line.reconcile([
+            {'id': liquidity_lines.id},
+            {'balance': 226.04, 'account_id': self.company_data['default_account_revenue'].id, 'name': "write-off"},
+        ])
+
+        self.assertRecordValues(statement_line.line_ids, [
+            {'amount_currency': 7541.66,    'debit': 6446.97,   'credit': 0.0},
+            {'amount_currency': 226.04,     'debit': 193.22,    'credit': 0.0},
+            {'amount_currency': -7767.70,   'debit': 0.0,       'credit': 6640.19},
+        ])