[FIX] account: reconciliation models: make auto_reconcile rules work properly with write-offs

- Create an invoice for 100
- Create a bank statement for 95
- Setup your reconciliation model so that it will match them and create a write-off for the remaining 5. Make it auto_reconciled.

=> Doing that, we expect the bank journal move to be created like this:

- 100 on payable/receivable, reconciled with the invoice
- 95 on the bank account
- 5 on the write-off account

This wasn't the case. Instead, Odoo created the following (correct from an accounting point of view, but weird):

- 95 on payable/receivable, reconciled with the invoice
- 5 on payable/receivable, not reconciled
- 95 on the bank account
- 5 on the write-off account

=> So an open balance of 5 was actually created. This was weird, and also caused an additional bug, as only the first payable/receivable line was reconciled with the invoice, making it only partially paid.

This commit restores the expected behavior.

addons/account/models/account_reconcile_model.py

@@ -393,6 +393,8 @@ class AccountReconcileModel(models.Model):
 
         partner = partner or st_line.partner_id
 
+        has_full_write_off= any(rec_mod_line.amount == 100.0 for rec_mod_line in self.line_ids)
+
         lines_vals_list = []
         amls = self.env['account.move.line'].browse(aml_ids)
         st_line_residual_before = st_line_residual
@@ -403,6 +405,9 @@ class AccountReconcileModel(models.Model):
             if aml.balance * st_line_residual > 0:
                 # Meaning they have the same signs, so they can't be reconciled together
                 assigned_balance = -aml.amount_residual
+            elif has_full_write_off:
+                assigned_balance = -aml.amount_residual
+                st_line_residual -= min(-aml.amount_residual, st_line_residual, key=abs)
             else:
                 assigned_balance = min(-aml.amount_residual, st_line_residual, key=abs)
                 st_line_residual -= assigned_balance

addons/account/tests/test_reconciliation_matching_rules.py

@@ -448,12 +448,14 @@ class TestReconciliationMatchingRules(AccountTestInvoicingCommon):
         ])
 
     def test_larger_invoice_auto_reconcile(self):
-        ''' Test auto reconciliation with an invoice with larger amount than the statement line's.'''
+        ''' Test auto reconciliation with an invoice with larger amount than the
+        statement line's, for rules without write-offs.'''
         self.bank_line_1.amount = 40
         self.invoice_line_1.move_id.payment_reference = self.bank_line_1.payment_ref
 
         self.rule_1.sequence = 2
         self.rule_1.auto_reconcile = True
+        self.rule_1.line_ids = [(5, 0, 0)]
 
         self._check_statement_matching(self.rule_1, {
             self.bank_line_1.id: {'aml_ids': [self.invoice_line_1.id], 'model': self.rule_1, 'status': 'reconciled', 'partner': self.bank_line_1.partner_id},
@@ -767,3 +769,24 @@ class TestReconciliationMatchingRules(AccountTestInvoicingCommon):
         }
 
         self.assertDictEqual(expected_write_off, to_compare)
+
+    def test_inv_matching_with_write_off_autoreconcile(self):
+        self.bank_line_1.amount = 95
+
+        self.rule_1.sequence = 2
+        self.rule_1.auto_reconcile = True
+        self.rule_1.match_total_amount_param = 90
+
+        self._check_statement_matching(self.rule_1, {
+            self.bank_line_1.id: {'aml_ids': [self.invoice_line_1.id], 'model': self.rule_1, 'status': 'reconciled', 'partner': self.bank_line_1.partner_id},
+            self.bank_line_2.id: {'aml_ids': []},
+        }, statements=self.bank_st)
+
+        # Check first line has been properly reconciled.
+        self.assertRecordValues(self.bank_line_1.line_ids, [
+            {'partner_id': self.partner_1.id, 'debit': 95.0, 'credit': 0.0, 'account_id': self.bank_journal.default_account_id.id, 'reconciled': False},
+            {'partner_id': self.partner_1.id, 'debit': 5.0, 'credit': 0.0, 'account_id': self.current_assets_account.id, 'reconciled': False},
+            {'partner_id': self.partner_1.id, 'debit': 0.0, 'credit': 100.0, 'account_id': self.invoice_line_1.account_id.id, 'reconciled': True},
+        ])
+
+        self.assertEqual(self.invoice_line_1.amount_residual, 0.0, "The invoice should have been fully reconciled")