fix(caldav): expand RRULE for recurring events

internal/icalfix/icalfix_test.go

@@ -69,3 +69,36 @@ func TestNormalizeTimeZonesLeavesUnknownAndIANAZonesAlone(t *testing.T) {
 		t.Fatalf("expected data to be unchanged, got:\n%s", got)
 	}
 }
+
+// TestNormalizeTimeZonesFixesVTIMEZONECRLFLine reproduces a real bug: the
+// standalone "TZID:<name>" property line inside a VTIMEZONE component
+// (as opposed to a "TZID=<name>" parameter on DTSTART/DTEND/etc.) was
+// never being normalized on real-world feeds, because every
+// Outlook/Exchange-published ICS uses CRLF line endings and Go's RE2 "$"
+// anchor in multi-line mode only matches immediately before a literal
+// "\n" — not before "\r\n". So on a line like
+// "TZID:W. Europe Standard Time\r\n", the old
+// `^TZID:([^\r\n]+)$` pattern never matched at all, leaving the
+// VTIMEZONE's own declared TZID un-normalized while every "TZID=..."
+// parameter elsewhere in the same object WAS normalized (that regex has
+// no such issue) — so nothing referencing the VTIMEZONE by name could
+// ever find it again. See internal/icssub.Series.referencedTimezones,
+// which depends on exactly this match to embed the right VTIMEZONE in a
+// synthetic per-series VCALENDAR.
+func TestNormalizeTimeZonesFixesVTIMEZONECRLFLine(t *testing.T) {
+	const raw = "BEGIN:VCALENDAR\r\n" +
+		"BEGIN:VTIMEZONE\r\n" +
+		"TZID:W. Europe Standard Time\r\n" +
+		"END:VTIMEZONE\r\n" +
+		"END:VCALENDAR\r\n"
+	const want = "BEGIN:VCALENDAR\r\n" +
+		"BEGIN:VTIMEZONE\r\n" +
+		"TZID:Europe/Berlin\r\n" +
+		"END:VTIMEZONE\r\n" +
+		"END:VCALENDAR\r\n"
+
+	got := string(NormalizeTimeZones([]byte(raw)))
+	if got != want {
+		t.Fatalf("CRLF-terminated VTIMEZONE TZID line was not normalized:\ngot:  %q\nwant: %q", got, want)
+	}
+}