Suppress RRULE occurrences replaced by RECURRENCE-ID exceptions

Message

When a recurring event has modified instances (VEVENT entries with RECURRENCE-ID), the original RRULE-generated occurrence for that date/time should be suppressed. Collect all RECURRENCE-ID timestamps and filter them from expanded results so only the exception instance appears, matching how calendar UIs like Fastmail handle this.

Changed

 src/sigil/caldav/event.sgl | 50 ++++++++++++++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 18 deletions(-)

Diff

src/sigil/caldav/event.sglmodified

@@ -91,25 +91,39 @@

(loop (cdr remaining) events))))))

;; Expand recurrence for all events that have RRULE.

−94

;; Non-recurring events (including exception instances with RECURRENCE-ID)

−95

;; are filtered by the date range to avoid returning out-of-range entries.

+94

;; Exception instances (RECURRENCE-ID) replace the RRULE-generated

+95

;; occurrence for that date — the original is suppressed.

+96

;; Non-recurring events are filtered by the date range.

(define (expand-all-events events start end)

−97

(let loop ((remaining events) (result '()))

−98

(if (null? remaining)

−99

(reverse result)

−100

(let ((ev (car remaining)))

−101

(if (ical-event-rrule ev)

−102

(loop (cdr remaining)

−103

(append (reverse (ical-expand-recurrence ev

−104

start: start end: end))

−105

result))

−106

;; Non-recurring: include only if within range

−107

(let ((ev-start (ical-event-dtstart ev)))

−108

(if (and ev-start

−109

(or (not start) (>= ev-start start))

−110

(or (not end) (< ev-start end)))

−111

(loop (cdr remaining) (cons ev result))

−112

(loop (cdr remaining) result))))))))

+98

;; Collect RECURRENCE-ID timestamps — these suppress RRULE occurrences

+99

(let ((exception-times

+100

(filter-map (lambda (ev)

+101

(ical-event-recurrence-id ev))

+102

events)))

+103

(let loop ((remaining events) (result '()))

+104

(if (null? remaining)

+105

(reverse result)

+106

(let ((ev (car remaining)))

+107

(if (ical-event-rrule ev)

+108

;; Expand, then remove occurrences replaced by exceptions

+109

(let ((expanded (ical-expand-recurrence ev

+110

start: start end: end)))

+111

(let ((filtered

+112

(if (null? exception-times)

+113

expanded

+114

(filter (lambda (occ)

+115

(not (member (ical-event-dtstart occ)

+116

exception-times)))

+117

expanded))))

+118

(loop (cdr remaining)

+119

(append (reverse filtered) result))))

+120

;; Non-recurring: include only if within range

+121

(let ((ev-start (ical-event-dtstart ev)))

+122

(if (and ev-start

+123

(or (not start) (>= ev-start start))

+124

(or (not end) (< ev-start end)))

+125

(loop (cdr remaining) (cons ev result))

+126

(loop (cdr remaining) result)))))))))

127

128

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;; ============================================================