[FIX] sale: create invoice when SO lines are empty

This error occurs when creating an invoice for a sale order with no SO line.

Steps to reproduce:
- Install 'sale_management' module
- Create a New SO and 'Add a Section' > Confirm
- Remove SO line > Create Invoice > Down Payment > Create Draft

Traceback:
TypeError: 'int' object is not iterable

At [1], the error occurs because self.order_line.mapped('sequence') returns an
empty list. The fallback value 10 is used, but since it's an
integer (not a list), it causes a TypeError.

[1]- https://github.com/odoo/odoo/blob/f101a9b6d65e34cf3d3175a341b87e3f14c44a02/addons/sale/models/sale_order.py#L2052

sentry-6601545000

closes odoo#210455

X-original-commit: 1436f6e
Signed-off-by: Victor Feyens (vfe) <[email protected]>
Signed-off-by: Aayush Modi (aamo) <[email protected]>

Author: aamo-odoo

addons/sale/models/sale_order.py

@@ -2029,7 +2029,7 @@ def _create_down_payment_lines_from_base_lines(self, down_payment_base_lines):
         :return The newly created SO lines.
         """
         self.ensure_one()
-        sequence = max(self.order_line.mapped('sequence') or 10) + 1
+        sequence = max(self.order_line.mapped('sequence') or [10]) + 1
         return self.env['sale.order.line'] \
             .with_context(sale_no_log_for_new_lines=True) \
             .create([
@@ -2051,7 +2051,7 @@ def _create_down_payment_section_line_if_needed(self):
         if any(line.display_type and line.is_downpayment for line in self.order_line):
             return
 
-        sequence = max(self.order_line.mapped('sequence') or 10) + 1
+        sequence = max(self.order_line.mapped('sequence') or [10]) + 1
         return self.env['sale.order.line'] \
             .with_context(sale_no_log_for_new_lines=True) \
             .create({

addons/sale/tests/test_sale_to_invoice.py

@@ -1330,3 +1330,27 @@ def test_refund_salesteam(self):
             invoice.team_id, team2,
             "Invoice team should be the same as the order's team",
         )
+
+    def test_invoice_from_order_without_lines(self):
+        """Test that an invoice can be created from a sale order with no product lines"""
+        sale_order = self.env['sale.order'].create({'partner_id': self.partner.id})
+        self.env['sale.order.line'].create({
+            'display_type': 'line_section',
+            'name': 'Test section',
+            'order_id': sale_order.id,
+        }).unlink()
+        sale_order.action_confirm()
+        wizard = self.env['sale.advance.payment.inv'].with_context({
+            'active_model': 'sale.order',
+            'active_ids': [sale_order.id],
+            'active_id': sale_order.id,
+            'default_journal_id': self.company_data['default_journal_sale'].id,
+        }).create({
+            'advance_payment_method': 'percentage',
+            'amount': 10,
+        })
+        action_values = wizard.create_invoices()
+
+        invoice = self.env['account.move'].browse(action_values['res_id'])
+        self.assertTrue(invoice)
+        self.assertEqual(invoice.partner_id, sale_order.partner_id)