fix(calendar-sync): drop declined events from synced output

The sync parsed PARTSTAT into a :STATUS: declined property but kept
the event. Meetings I'd declined still landed in dcal.org / gcal.org
and showed on the agenda. I added a pure --filter-declined helper
called inside --parse-ics after event collection, plus the
calendar-sync-skip-declined defvar (default t) so it can be flipped
off without code changes.

The .ics feed and the Calendar API can disagree on PARTSTAT. OOO
auto-declines sometimes only write API-side, so a few declined
events may still slip through. I'm calling this out because the
filter looks absolute from the agenda but isn't.

Tests cover Normal/Boundary/Error (11 cases). Full suite is green.

1 files changed, 129 insertions, 0 deletions

diff --git a/tests/test-calendar-sync--filter-declined.el b/tests/test-calendar-sync--filter-declined.el
new file mode 100644
index 00000000..41fc99a1
--- /dev/null
+++ b/tests/test-calendar-sync--filter-declined.el
@@ -0,0 +1,129 @@
+;;; test-calendar-sync--filter-declined.el --- Tests for filter-declined  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Unit tests for calendar-sync--filter-declined function.
+;; Drops events whose :status is "declined" when calendar-sync-skip-declined
+;; is non-nil; otherwise returns the input list unchanged.
+;; Covers Normal, Boundary, and Error cases.
+
+;;; Code:
+
+(require 'ert)
+(require 'calendar-sync)
+
+;;; Test Data
+
+(defun test-filter-declined--make-events ()
+  "Return a small mixed-status event list."
+  (list (list :uid "a" :summary "Accepted meeting"  :status "accepted")
+        (list :uid "b" :summary "Declined meeting"  :status "declined")
+        (list :uid "c" :summary "Tentative meeting" :status "tentative")
+        (list :uid "d" :summary "Unknown status"    :status nil)
+        (list :uid "e" :summary "Needs action"      :status "needs-action")))
+
+;;; Normal Cases
+
+(ert-deftest test-calendar-sync--filter-declined-normal-drops-declined ()
+  "Normal: declined events are removed when the toggle is on."
+  (let ((calendar-sync-skip-declined t)
+        (events (test-filter-declined--make-events)))
+    (let ((result (calendar-sync--filter-declined events)))
+      (should (= 4 (length result)))
+      (should-not (cl-find "declined" result
+                           :key (lambda (e) (plist-get e :status))
+                           :test #'equal)))))
+
+(ert-deftest test-calendar-sync--filter-declined-normal-keeps-accepted ()
+  "Normal: accepted events are preserved."
+  (let ((calendar-sync-skip-declined t)
+        (events (test-filter-declined--make-events)))
+    (let ((result (calendar-sync--filter-declined events)))
+      (should (cl-find "accepted" result
+                       :key (lambda (e) (plist-get e :status))
+                       :test #'equal)))))
+
+(ert-deftest test-calendar-sync--filter-declined-normal-keeps-tentative ()
+  "Normal: tentative events are preserved (only declined is dropped)."
+  (let ((calendar-sync-skip-declined t)
+        (events (test-filter-declined--make-events)))
+    (let ((result (calendar-sync--filter-declined events)))
+      (should (cl-find "tentative" result
+                       :key (lambda (e) (plist-get e :status))
+                       :test #'equal)))))
+
+(ert-deftest test-calendar-sync--filter-declined-normal-keeps-needs-action ()
+  "Normal: needs-action events are preserved."
+  (let ((calendar-sync-skip-declined t)
+        (events (test-filter-declined--make-events)))
+    (let ((result (calendar-sync--filter-declined events)))
+      (should (cl-find "needs-action" result
+                       :key (lambda (e) (plist-get e :status))
+                       :test #'equal)))))
+
+(ert-deftest test-calendar-sync--filter-declined-normal-keeps-nil-status ()
+  "Normal: events with no PARTSTAT (nil :status) are preserved.
+Events without an attendee block (one-person events, ICS feeds that
+omit attendee data) come through with :status nil and must not be
+filtered."
+  (let ((calendar-sync-skip-declined t)
+        (events (test-filter-declined--make-events)))
+    (let ((result (calendar-sync--filter-declined events)))
+      (should (cl-find nil result
+                       :key (lambda (e) (plist-get e :status))
+                       :test #'equal)))))
+
+(ert-deftest test-calendar-sync--filter-declined-normal-toggle-off-keeps-all ()
+  "Normal: when the toggle is nil, declined events pass through."
+  (let ((calendar-sync-skip-declined nil)
+        (events (test-filter-declined--make-events)))
+    (let ((result (calendar-sync--filter-declined events)))
+      (should (= 5 (length result)))
+      (should (cl-find "declined" result
+                       :key (lambda (e) (plist-get e :status))
+                       :test #'equal)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-calendar-sync--filter-declined-boundary-empty-list ()
+  "Boundary: empty event list returns empty list under either toggle setting."
+  (let ((calendar-sync-skip-declined t))
+    (should (null (calendar-sync--filter-declined '()))))
+  (let ((calendar-sync-skip-declined nil))
+    (should (null (calendar-sync--filter-declined '())))))
+
+(ert-deftest test-calendar-sync--filter-declined-boundary-all-declined ()
+  "Boundary: list of only declined events returns empty list."
+  (let ((calendar-sync-skip-declined t)
+        (events (list (list :uid "a" :status "declined")
+                      (list :uid "b" :status "declined")
+                      (list :uid "c" :status "declined"))))
+    (should (null (calendar-sync--filter-declined events)))))
+
+(ert-deftest test-calendar-sync--filter-declined-boundary-none-declined ()
+  "Boundary: list with zero declined events is returned unchanged in length."
+  (let ((calendar-sync-skip-declined t)
+        (events (list (list :uid "a" :status "accepted")
+                      (list :uid "b" :status "tentative")
+                      (list :uid "c" :status nil))))
+    (should (= 3 (length (calendar-sync--filter-declined events))))))
+
+(ert-deftest test-calendar-sync--filter-declined-boundary-case-mismatch-not-dropped ()
+  "Boundary: a non-lowercase \"Declined\" is not dropped.
+`calendar-sync--find-user-status' downcases PARTSTAT before storing,
+so any :status reaching the filter is already lowercase. Anything
+else (uppercase, mixed-case) is an upstream protocol mismatch and we
+keep the event rather than filter it on a fuzzy match."
+  (let ((calendar-sync-skip-declined t)
+        (events (list (list :uid "a" :status "Declined")
+                      (list :uid "b" :status "DECLINED"))))
+    (should (= 2 (length (calendar-sync--filter-declined events))))))
+
+;;; Error Cases
+
+(ert-deftest test-calendar-sync--filter-declined-error-nil-input ()
+  "Error: nil input returns nil (no crash)."
+  (let ((calendar-sync-skip-declined t))
+    (should (null (calendar-sync--filter-declined nil)))))
+
+(provide 'test-calendar-sync--filter-declined)
+;;; test-calendar-sync--filter-declined.el ends here