[FIX] l10n_eu_oss: OSS tax on root company only

The aim of this commit is to make the OSS feature instanciate the taxes
on the the root company .

Context: currently, when a company has a branch, the OSS feature tries
to instanciate the taxes on both the root company and the branch
company.
This was brought up by a constrains that prevents you from instanciating
2 tax with the same name on the same company.

Before the commit:
The feature tries to instanciate the OSS taxes on both the root and
branch company.

After the commit:
The taxes are only instanciated on the root company.

closes odoo/odoo#141347

Task-id: 3573252
Signed-off-by: William André (wan) <wan@odoo.com>
Signed-off-by: Brice Bartoletti (bib) <bib@odoo.com>

addons/l10n_eu_oss/models/res_company.py

@@ -26,7 +26,7 @@ class Company(models.Model):
         oss_tax_groups = self.env['ir.model.data'].search([
             ('module', '=', 'l10n_eu_oss'),
             ('model', '=', 'account.tax.group')])
-        for company in self:
+        for company in self.root_id:  # instantiate OSS taxes on the root company only
             invoice_repartition_lines, refund_repartition_lines = company._get_repartition_lines_oss()
             taxes = self.env['account.tax'].search([
                 *self.env['account.tax']._check_company_domain(company),

addons/l10n_eu_oss/tests/test_oss.py

@@ -1,7 +1,8 @@
 # -*- coding: utf-8 -*-
 
-from odoo.addons.l10n_eu_oss.models.eu_tag_map import EU_TAG_MAP
+from odoo import Command
 from odoo.addons.account.tests.common import AccountTestInvoicingCommon
+from odoo.addons.l10n_eu_oss.models.eu_tag_map import EU_TAG_MAP
 from odoo.tests import tagged
 
 
@@ -24,8 +25,25 @@ class TestOSSBelgium(OssTemplateTestCase):
     @classmethod
     def setUpClass(cls, chart_template_ref='be_comp'):
         super().setUpClass(chart_template_ref)
-        cls.company_data['company'].country_id = cls.env.ref('base.be')
-        cls.company_data['company']._map_eu_taxes()
+        cls.root_company = cls.company_data['company']
+        cls.root_company.country_id = cls.env.ref('base.be')
+        cls.root_company.child_ids = [Command.create({'name': 'Branch A'})]
+        cls.cr.precommit.run()  # load the CoA
+        cls.child_company = cls.root_company.child_ids
+        cls.child_company.child_ids = [Command.create({'name': 'sub Branch B'})]
+        cls.sub_child_company = cls.root_company.child_ids.child_ids
+        cls.cr.precommit.run()  # load the CoA
+
+        cls.sub_child_company._map_eu_taxes()
+
+    def test_oss_tax_should_be_instantiated_on_root_company(self):
+        # simulate sub child selection in the switcher
+        self.env.user.company_id, self.env.user.company_ids = self.sub_child_company, self.sub_child_company
+
+        another_eu_country_code = (self.env.ref('base.europe').country_ids - self.sub_child_company.country_id)[0].code
+        tax_oss = self.env['account.tax'].search([('name', 'ilike', f'%{another_eu_country_code}%')], limit=1)
+        self.assertTrue(tax_oss)
+        self.assertEqual(tax_oss.company_id, self.root_company)
 
     def test_country_tag_from_belgium(self):
         """