time: add MMM support for parse_format() (#19284)

vlib/time/date_time_parser.v

@@ -88,6 +88,19 @@ fn (mut p DateTimeParser) must_be_valid_month() !int {
 	return error_invalid_time(0, 'invalid month name')
 }
 
+fn (mut p DateTimeParser) must_be_valid_three_letter_month() !int {
+	for month_number := 1; month_number < long_months.len; month_number++ {
+		if p.current_pos_datetime + 3 < p.datetime.len {
+			month_three_letters := p.datetime[p.current_pos_datetime..p.current_pos_datetime + 3]
+			if months_string[(month_number - 1) * 3..month_number * 3] == month_three_letters {
+				p.current_pos_datetime += 3
+				return month_number
+			}
+		}
+	}
+	return error_invalid_time(0, 'invalid month three letters')
+}
+
 fn (mut p DateTimeParser) must_be_valid_week_day(letters int) !string {
 	val := p.next(letters)!
 	for v in long_days {
@@ -171,6 +184,9 @@ fn (mut p DateTimeParser) parse() !Time {
 					return error_invalid_time(0, 'month must be  between 01 and 12')
 				}
 			}
+			'MMM' {
+				month_ = p.must_be_valid_three_letter_month() or { return err }
+			}
 			'MMMM' {
 				month_ = p.must_be_valid_month() or { return err }
 			}

vlib/time/time_test.v

@@ -336,3 +336,11 @@ fn test_plus_equals_duration() {
 	d += time.second
 	assert d == 2 * time.second
 }
+
+fn test_parse_three_letters_month() {
+	tm := time.now()
+	format := 'MMM DD HH:mm:ss YYYY'
+	tm_s := tm.custom_format(format)
+	tm_tm := time.parse_format(tm_s, format)!
+	assert tm_tm.month == tm.month
+}