[IMP] mail: notify author of internal notes when replied through gateway

Currently if an user mentions someone in an internal note he is not
notified of any reply as replies create internal notes. This commit
ensure the author of the first note is notified of the reply even
if it is still an internal note.

Tests have been updated accordingly.

addons/mail/models/mail_thread.py

@@ -1180,7 +1180,7 @@ class MailThread(models.AbstractModel):
     def message_route_process(self, message, message_dict, routes):
         self = self.with_context(attachments_mime_plainxml=True) # import XML attachments as text
         # postpone setting message_dict.partner_ids after message_post, to avoid double notifications
-        partner_ids = message_dict.pop('partner_ids', [])
+        original_partner_ids = message_dict.pop('partner_ids', [])
         thread_id = False
         for model, thread_id, custom_values, user_id, alias in routes or ():
             if model:
@@ -1206,13 +1206,23 @@ class MailThread(models.AbstractModel):
                 Model = self.env['mail.thread']
             if not hasattr(Model, 'message_post'):
                 Model = self.env['mail.thread'].with_context(thread_model=model)
-            internal = message_dict.pop('internal', False)
-            new_msg = Model.browse(thread_id).message_post(subtype=internal and 'mail.mt_note' or 'mail.mt_comment', **message_dict)
 
-            if partner_ids:
+            # replies to internal message are considered as notes, but parent message
+            # author is added in recipients to ensure he is notified of a private answer
+            partner_ids = []
+            if message_dict.pop('internal', False):
+                subtype = 'mail.mt_note'
+                if message_dict.get('parent_id'):
+                    parent_message = self.env['mail.message'].sudo().browse(message_dict['parent_id'])
+                    partner_ids = [(4, parent_message.author_id.id)]
+            else:
+                subtype = 'mail.mt_comment'
+            new_msg = Model.browse(thread_id).message_post(subtype=subtype, partner_ids=partner_ids, **message_dict)
+
+            if original_partner_ids:
                 # postponed after message_post, because this is an external message and we don't want to create
                 # duplicate emails due to notifications
-                new_msg.write({'partner_ids': partner_ids})
+                new_msg.write({'partner_ids': original_partner_ids})
         return thread_id
 
     @api.model

addons/mail/tests/test_mail_features.py

@@ -202,7 +202,7 @@ class TestMessagePost(TestMail):
         reply = self.group_pigs.message_ids - msg
         self.assertTrue(reply)
         self.assertEqual(reply.subtype_id, self.env.ref('mail.mt_note'))
-        self.assertEqual(reply.needaction_partner_ids, self.env['res.partner'])
+        self.assertEqual(reply.needaction_partner_ids, self.user_employee.partner_id)
 
     @mute_logger('odoo.addons.mail.models.mail_mail')
     def test_message_compose(self):