Fix SUN-SUN day-of-week range in CronExpression

spring-context/src/main/java/org/springframework/scheduling/support/BitsCronField.java

@@ -161,8 +161,9 @@ private static ValueRange parseRange(String value, Type type) {
 				int max = Integer.parseInt(value, hyphenPos + 1, value.length(), 10);
 				min = type.checkValidValue(min);
 				max = type.checkValidValue(max);
-				if (type == Type.DAY_OF_WEEK && min == 7) {
-					// If used as a minimum in a range, Sunday means 0 (not 7)
+				if (type == Type.DAY_OF_WEEK && min == 7 && max != 7) {
+					// If used as a minimum in a range, Sunday means 0 (not 7),
+					// unless the range also ends with Sunday, as in "SUN-SUN"
 					min = 0;
 				}
 				return ValueRange.of(min, max);

spring-context/src/test/java/org/springframework/scheduling/support/BitsCronFieldTests.java

@@ -55,6 +55,7 @@ void parse() {
 		assertThat(BitsCronField.parseDaysOfWeek("0")).has(set(7, 7)).has(clearRange(0, 6));
 		assertThat(BitsCronField.parseDaysOfWeek("7-5")).has(clear(0)).has(setRange(1, 5))
 				.has(clear(6)).has(set(7));
+		assertThat(BitsCronField.parseDaysOfWeek("7-7")).has(clearRange(0, 6)).has(set(7));
 	}
 
 	@Test

spring-context/src/test/java/org/springframework/scheduling/support/CronExpressionTests.java

@@ -1328,6 +1328,25 @@ void sundayToFriday() {
 		assertThat(actual.getDayOfWeek()).isEqualTo(SUNDAY);
 	}
 
+	@Test
+	void sundayToSunday() {
+		CronExpression expression = CronExpression.parse("0 0 0 ? * SUN-SUN");
+
+		LocalDateTime last = LocalDateTime.of(2021, 2, 25, 15, 0);
+		LocalDateTime expected = LocalDateTime.of(2021, 2, 28, 0, 0);
+		LocalDateTime actual = expression.next(last);
+		assertThat(actual).isNotNull();
+		assertThat(actual).isEqualTo(expected);
+		assertThat(actual.getDayOfWeek()).isEqualTo(SUNDAY);
+
+		last = actual;
+		expected = LocalDateTime.of(2021, 3, 7, 0, 0);
+		actual = expression.next(last);
+		assertThat(actual).isNotNull();
+		assertThat(actual).isEqualTo(expected);
+		assertThat(actual.getDayOfWeek()).isEqualTo(SUNDAY);
+	}
+
 	@Test
 	void daylightSaving() {
 		CronExpression cronExpression = CronExpression.parse("0 0 9 * * *");