[FIX] mail: prevent inconsistencies when using message reply

closes odoo/odoo#86060

X-original-commit: 81ddfad51e9b35db8d14e1fb14aa24596b6af767
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/models/mail_channel.py

@@ -579,7 +579,8 @@ class Channel(models.Model):
     def _message_compute_parent_id(self, parent_id):
         # super() unravels the chain of parents to set parent_id as the first
         # ancestor. We don't want that in channel.
-        return parent_id
+        parent_message = self.env['mail.message'].search([('id', '=', parent_id), ('model', '=', 'mail.channel'), ('res_id', '=', self.id)])
+        return parent_message.id
 
     @api.returns('mail.message', lambda value: value.id)
     def message_post(self, *, message_type='notification', **kwargs):

addons/mail/tests/test_mail_channel.py

@@ -354,6 +354,14 @@ class TestChannelInternals(MailCommon):
             "Last message id should stay the same after mark channel as seen with an older message"
         )
 
+    def test_channel_message_post_should_not_allow_adding_wrong_parent(self):
+        channels = self.env['mail.channel'].create([{'name': '1'}, {'name': '2'}])
+        message = self._add_messages(channels[0], 'Body1')
+        message_format2 = channels[1].message_post(body='Body2', parent_id=message.id)
+        self.assertFalse(message_format2['parent_id'], "should not allow parent from wrong thread")
+        message_format3 = channels[1].message_post(body='Body3', parent_id=message.id + 100)
+        self.assertFalse(message_format3['parent_id'], "should not allow non-existing parent")
+
     @mute_logger('odoo.models.unlink')
     def test_channel_unsubscribe_auto(self):
         """ Archiving / deleting a user should automatically unsubscribe related