[FIX] calendar: support writing attendee_ids with ids

Before this commit, attempting to do
`self.env['calendar.event'].write({'partner_ids': [0, 1, 2]})`
would give a traceback as the method that updates attendees
only supports parsing commands, not ids.

This is a problem as that method is called from 'write' and other methods
with the assumption that partner_ids can only contain commands.

This will not be the case when using a gantt view and grouping
by partner_ids for example, and cannot be worked around.

task-3452277

closes odoo/odoo#146446

X-original-commit: 88e191132bf40a4e3090077f1fd0077e649eb7fb
Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>
Signed-off-by: Renaud Thiry (reth) <reth@odoo.com>

addons/calendar/models/calendar_event.py

@@ -789,6 +789,11 @@ class Meeting(models.Model):
 
         removed_partner_ids = []
         added_partner_ids = []
+
+        # if commands are just integers, assume they are ids with the intent to `Command.set`
+        if partner_commands and isinstance(partner_commands[0], int):
+            partner_commands = [Command.set(partner_commands)]
+
         for command in partner_commands:
             op = command[0]
             if op in (2, 3, Command.delete, Command.unlink):  # Remove partner

addons/calendar/tests/test_attendees.py

@@ -68,6 +68,11 @@ class TestEventNotifications(TransactionCase):
         events.partner_ids = self.partner
         self.assertEqual(len(events.attendee_ids), 2, "It should have created one attendee per event")
 
+    def test_attendee_added_write(self):
+        """Test that writing ids directly on partner_ids instead of commands is handled."""
+        self.event.write({'partner_ids': [self.partner.id]})
+        self.assertEqual(self.event.attendee_ids.partner_id, self.partner, "It should be linked to the partner")
+
     def test_existing_attendee_added(self):
         self.event.partner_ids = self.partner
         attendee = self.event.attendee_ids