[Evolution-hackers] e_cal_client_check_timezones() + e_cal_client_tzlookup() + Could not retrieve calendar time zone: Invalid object

[Patrick Ohly <patrick ohly gmx de>]

Hello!

I've started testing a version of SyncEvolution which uses the
EBook/CalClient API. The import test fails for a VEVENT which uses a
custom timezone:

BEGIN:VCALENDAR
PRODID:-//Ximian//NONSGML Evolution Calendar//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:EST/EDT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:19671029T020000
RRULE:FREQ=MONTHLY;INTERVAL=12;BYDAY=-1SU
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:19870405T020000
RRULE:FREQ=MONTHLY;INTERVAL=12;BYDAY=1SU
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
UID:20060416T205224Z-4272-727-1-251@gollum
DTSTAMP:20060416T205224Z
DTSTART;TZID=EST/EDT:20060406T140000
DTEND;TZID=EST/EDT:20060406T143000
TRANSP:OPAQUE
SEQUENCE:2
SUMMARY:timezone New York with custom definition for 2006
CLASS:PUBLIC
CREATED:20060416T205301Z
LAST-MODIFIED:20120531T085920Z
END:VEVENT
END:VCALENDAR

e_cal_client_check_timezones() fails with "Could not retrieve calendar
time zone: Invalid object". This comes from the attempt to look up
"EST/EDT" in an empty calendar:

icaltimezone *
e_cal_client_tzlookup (const gchar *tzid,
                       gconstpointer ecalclient,
                       GCancellable *cancellable,
                       GError **error)
{
...
        if (e_cal_client_get_timezone_sync (cal_client, tzid, &zone, cancellable, &local_error)) {
                g_warn_if_fail (local_error == NULL);
                return zone;
        }

        if (g_error_matches (local_error, E_CAL_CLIENT_ERROR, E_CAL_CLIENT_ERROR_OBJECT_NOT_FOUND)) {
                /* We had to trigger this error to check for the
                 * timezone existance, clear it and return NULL. */
                g_clear_error (&local_error);
        }
...

It's normal that e_cal_client_get_timezone_sync() fails. But it fails with an unexpected error:

signal sender=:1.3 -> dest=(null destination) serial=94 path=/org/gnome/evolution/dataserver/Calendar/1636/9; interface=org.gnome.evolution.dataserver.Calendar; member=get_timezone_done
   uint32 18
   string "org.gnome.evolution.dataserver.Calendar.InvalidObject"
   string "Could not retrieve calendar time zone: Invalid object"
   string ""

Therefore the error is not cleared and e_cal_client_check_timezones()
aborts instead of accepting the "EST/EDT" time zone as it is.

This works in Evolution itself, probably because it let's the backend
itself do the e_cal_client_check_timezones() with a different lookup
function.

What is the preferred way of fixing this?

We could define that e_cal_client_get_timezone*() must return the
E_CAL_CLIENT_ERROR_OBJECT_NOT_FOUND error when the time zone doesn't
exist and fix it to do so. Or we could make the error check in
e_cal_client_tzlookup() more liberal and ignore all E_CAL_CLIENT_ERRORs.

The latter might be easier, in particular considering that multiple
different calendar backends might need fixing to reliably return
E_CAL_CLIENT_ERROR_OBJECT_NOT_FOUND.

-- 
Bye, Patrick Ohly
--  
Patrick Ohly gmx de
http://www.estamos.de/