From a9e61207f6c806271cbc69fe27fde04b22e34e0a Mon Sep 17 00:00:00 2001
From: Craig Jennings <c@cjennings.net>
Date: Mon, 13 Jul 2026 12:12:35 -0500
Subject: bug: fixing exdate lines and adding tests

---
 modules/calendar-sync-recurrence.el      | 15 +++++++++------
 tests/test-calendar-sync--get-exdates.el | 29 +++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/modules/calendar-sync-recurrence.el b/modules/calendar-sync-recurrence.el
index 72576a6f..bc1cc92f 100644
--- a/modules/calendar-sync-recurrence.el
+++ b/modules/calendar-sync-recurrence.el
@@ -193,21 +193,24 @@ Handles both simple values and values with parameters like TZID."
   (when (and event-str (stringp event-str) (not (string-empty-p event-str)))
     (let ((exdates '())
           (pos 0))
-      ;; Find all EXDATE lines
+      ;; Find all EXDATE lines.  One line may carry several comma-separated
+      ;; datetimes (RFC 5545); split them so each is excluded individually.
       (while (string-match "^EXDATE[^:\n]*:\\([^\n]+\\)" event-str pos)
-        (push (match-string 1 event-str) exdates)
+        (dolist (val (split-string (match-string 1 event-str) "," t))
+          (push val exdates))
         (setq pos (match-end 0)))
       (nreverse exdates))))
 
 (defun calendar-sync--get-exdate-line (event-str exdate-value)
   "Find the full EXDATE line containing EXDATE-VALUE from EVENT-STR.
 Returns the complete line like
-`EXDATE;TZID=America/New_York:20260210T130000'.
-Returns nil if not found."
+`EXDATE;TZID=America/New_York:20260210T130000'.  Matches the value anywhere
+in the value list, so a comma-separated line's shared TZID reaches every
+value on it.  Returns nil if not found."
   (when (and event-str (stringp event-str) exdate-value)
-    (let ((pattern (format "^\\(EXDATE[^:]*:%s\\)" (regexp-quote exdate-value))))
+    (let ((pattern (format "^EXDATE[^:\n]*:[^\n]*%s" (regexp-quote exdate-value))))
       (when (string-match pattern event-str)
-        (match-string 1 event-str)))))
+        (match-string 0 event-str)))))
 
 (defalias 'calendar-sync--parse-exdate #'calendar-sync--parse-ics-datetime
   "Parse EXDATE value. See `calendar-sync--parse-ics-datetime'.")
diff --git a/tests/test-calendar-sync--get-exdates.el b/tests/test-calendar-sync--get-exdates.el
index 3283bbae..981a1857 100644
--- a/tests/test-calendar-sync--get-exdates.el
+++ b/tests/test-calendar-sync--get-exdates.el
@@ -103,6 +103,35 @@ END:VEVENT"))
       (should (= 1 (length result)))
       (should (string= "20260210T130000" (car result))))))
 
+(ert-deftest test-calendar-sync--get-exdates-boundary-comma-separated-returns-all ()
+  "Boundary: comma-separated EXDATE values on one line are each returned.
+RFC 5545 permits multiple datetimes per EXDATE line; missing the split
+drops those exclusions, so cancelled instances resurrect in the agenda."
+  (let ((event "BEGIN:VEVENT
+DTSTART:20260203T130000
+RRULE:FREQ=WEEKLY;BYDAY=TU
+EXDATE:20260210T130000,20260217T130000,20260224T130000
+SUMMARY:Weekly Meeting
+END:VEVENT"))
+    (let ((result (calendar-sync--get-exdates event)))
+      (should (= 3 (length result)))
+      (should (member "20260210T130000" result))
+      (should (member "20260217T130000" result))
+      (should (member "20260224T130000" result)))))
+
+(ert-deftest test-calendar-sync--get-exdates-boundary-comma-separated-with-tzid ()
+  "Boundary: comma-separated EXDATE values sharing a TZID are each returned."
+  (let ((event "BEGIN:VEVENT
+DTSTART;TZID=America/New_York:20260203T130000
+RRULE:FREQ=WEEKLY;BYDAY=TU
+EXDATE;TZID=America/New_York:20260210T130000,20260217T130000
+SUMMARY:Weekly Meeting
+END:VEVENT"))
+    (let ((result (calendar-sync--get-exdates event)))
+      (should (= 2 (length result)))
+      (should (member "20260210T130000" result))
+      (should (member "20260217T130000" result)))))
+
 ;;; Error Cases
 
 (ert-deftest test-calendar-sync--get-exdates-error-empty-string-returns-nil ()
-- 
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