Allow properties to exist after components

calendar.go

@@ -679,7 +679,42 @@ func parseCalendarFromHttpRequest(client HttpClientLike, request *http.Request)
 	return cal, err
 }
 
+// ParseOption provides functional options for ParseCalendar
+type ParseOption func(*parseConfig) error
+
+type parseConfig struct {
+	allowPropertiesAfterComponents bool
+}
+
+// WithRelaxedParsing allows properties to appear after components have started,
+// which is technically non-compliant with RFC 5545 but occurs in real-world files
+func WithRelaxedParsing() ParseOption {
+	return func(cfg *parseConfig) error {
+		cfg.allowPropertiesAfterComponents = true
+		return nil
+	}
+}
+
 func ParseCalendar(r io.Reader) (*Calendar, error) {
+	// Default behavior maintains backward compatibility (strict mode)
+	return ParseCalendarWithOptions(r)
+}
+
+func ParseCalendarWithOptions(r io.Reader, options ...ParseOption) (*Calendar, error) {
+	cfg := &parseConfig{
+		allowPropertiesAfterComponents: false, // default to strict RFC compliance
+	}
+
+	for _, opt := range options {
+		if err := opt(cfg); err != nil {
+			return nil, fmt.Errorf("invalid parse option: %w", err)
+		}
+	}
+
+	return parseCalendarInternal(r, cfg)
+}
+
+func parseCalendarInternal(r io.Reader, cfg *parseConfig) (*Calendar, error) {
 	state := "begin"
 	c := &Calendar{}
 	cs := NewCalendarStream(r)
@@ -753,7 +788,13 @@ func ParseCalendar(r io.Reader) (*Calendar, error) {
 					c.Components = append(c.Components, co)
 				}
 			default:
-				return nil, errors.New("malformed calendar; expected begin or end")
+				if cfg.allowPropertiesAfterComponents {
+					// Allow properties between components (non-standard but occurs in real-world ICS files)
+					// These properties are added to the calendar properties list
+					c.CalendarProperties = append(c.CalendarProperties, CalendarProperty{*line})
+				} else {
+					return nil, errors.New("malformed calendar; expected begin or end")
+				}
 			}
 		case "end":
 			return nil, errors.New("malformed calendar; unexpected end")

calendar_test.go

@@ -284,9 +284,10 @@ END:VCALENDAR
 
 func TestParseCalendar(t *testing.T) {
 	testCases := []struct {
-		name   string
-		input  string
-		output string
+		name        string
+		input       string
+		output      string
+		parseOptions []ParseOption // Add options field
 	}{
 		{
 			name: "test custom fields in calendar",
@@ -379,13 +380,59 @@ RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=SU
 CLASS:PUBLIC
 END:VEVENT
 END:VCALENDAR
+`,
+		},
+		{
+			name: "test properties after components",
+			input: `BEGIN:VCALENDAR
+VERSION:2.0
+BEGIN:VTIMEZONE
+TZID:Europe/London
+BEGIN:STANDARD
+TZOFFSETFROM:+0100
+TZOFFSETTO:+0000
+DTSTART:19701025T020000
+END:STANDARD
+END:VTIMEZONE
+TIMEZONE-ID:VT
+X-WR-TIMEZONE:VT
+BEGIN:VEVENT
+DTSTART:20230101T120000Z
+SUMMARY:Test Event
+END:VEVENT
+END:VCALENDAR
+`,
+			parseOptions: []ParseOption{WithRelaxedParsing()}, // Use relaxed parsing for this test
+			output: `BEGIN:VCALENDAR
+VERSION:2.0
+TIMEZONE-ID:VT
+X-WR-TIMEZONE:VT
+BEGIN:VTIMEZONE
+TZID:Europe/London
+BEGIN:STANDARD
+TZOFFSETFROM:+0100
+TZOFFSETTO:+0000
+DTSTART:19701025T020000
+END:STANDARD
+END:VTIMEZONE
+BEGIN:VEVENT
+DTSTART:20230101T120000Z
+SUMMARY:Test Event
+END:VEVENT
+END:VCALENDAR
 `,
 		},
 	}
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			c, err := ParseCalendar(strings.NewReader(tc.input))
+			var c *Calendar
+			var err error
+			if len(tc.parseOptions) > 0 {
+				c, err = ParseCalendarWithOptions(strings.NewReader(tc.input), tc.parseOptions...)
+			} else {
+				c, err = ParseCalendar(strings.NewReader(tc.input))
+			}
 			if !assert.NoError(t, err) {
 				return
 			}