Re: ox-icalendar: Filter todo-types

[Jack Kamm <jackkamm@gmail.com>]

Michaël Cadilhac <michael@cadilhac.name> writes:

> I have a task that was recurring, which I KILLED a few weeks ago.  It
> now looks like:
>
> ** KILLED Do the right thing
>    SCHEDULED: <2023-07-14 Fri +1w>
>
> ox-icalendar still exports it every week, because I have
> 'event-if-not-todo in org-icalendar-use-scheduled (which is the
> behavior I want for some other headers).
>
> BEGIN:VEVENT
> DTSTAMP:20240622T163042Z
> UID:SC-671b3d13-f985-472a-be33-b4eeb298f2cd
> DTSTART;VALUE=DATE:20230714
> DTEND;VALUE=DATE:20230715
> RRULE:FREQ=WEEKLY;INTERVAL=1
> SUMMARY:S: KILLED Do the right thing :
> CATEGORIES:todos
> END:VEVENT
>
> Would it be acceptable to add a variable to filter todo-types, e.g.,
> with a variable org-icalendar-excluded-todo-types?  More generally,
> one could think of introducing a variable:
>    org-icalendar-entry-filter
> which receives the ENTRY argument of org-icalendar-entry, and would
> return non-nil if the entry is to be treated.  (This is basically what
> I do using an advice.)

I agree ox-icalendar should have an option to exclude certain
todo-keywords from export.

However I think the option should also be flexible to allow exporting
todo-keywords as different STATUS:

https://datatracker.ietf.org/doc/html/rfc5545#section-3.8.1.11

For example, in your case it might make more sense to export the task as
CANCELLED in iCalendar.

I think I'd rather have a customization option for this than a filter
function. That way, other Lisp programs that import ICS to Org (such as
org-caldav) could refer to this option to interoperate with ox-icalendar
for 2-way sync.

Perhaps we could have an option ox-icalendar-export-todo-keywords-as
which could determine whether a keyword should be exported, and if so
with what status, e.g.:

(defcustom ox-icalendar-export-todo-keywords-as
 '((no-export . ("SKIP"))
   (cancelled . ("KILLED" "CANCELLED"))
   (in-process . ("PROG"))))

By default, todo-keywords not in the list would be exported with status
"NEEDS-ACTION" or "COMPLETED", depending on whether the keyword is a
done state.

What do you think?