fix: Sundays can begin weekday ranges (#320)

src/cron-parser.ts

@@ -128,7 +128,7 @@ function parseElement(element: string, constraint: IConstraint): Set<number> {
 	}
 
 	// If it is a range, get start and end of the range.
-	const parsedStart =
+	let parsedStart =
 		rangeSegments[1] === '*'
 			? constraint.min
 			: parseSingleElement(rangeSegments[2])
@@ -138,6 +138,16 @@ function parseElement(element: string, constraint: IConstraint): Set<number> {
 			? constraint.max
 			: parseSingleElement(rangeSegments[3])
 
+	// need to catch Sunday, which gets parsed here as 7, but is also legitimate at the start of a range as 0, to avoid the out of order error
+	if (
+		constraint === weekdayConstraint &&
+		parsedStart === 7 &&
+		// this check ensures that sun-sun is not incorrectly parsed as [0,1,2,3,4,5,6]
+		parsedEnd !== 7
+	) {
+		parsedStart = 0
+	}
+
 	if (parsedStart > parsedEnd) {
 		throw new Error(
 			`Failed to parse ${element}: Invalid range (start: ${parsedStart}, end: ${parsedEnd}).`,

test/cron-parser.test.ts

@@ -310,6 +310,24 @@ describe('parseCronExpression', () => {
 			months: [0],
 			weekdays: [4, 5, 6],
 		})
+
+		expect(parseCronExpression('0 0 0 1 1 Sun-wed,Fri')).toMatchObject({
+			seconds: [0],
+			minutes: [0],
+			hours: [0],
+			days: [1],
+			months: [0],
+			weekdays: [0, 1, 2, 3, 5],
+		})
+
+		expect(parseCronExpression('0 0 0 1 1 sun-sun')).toMatchObject({
+			seconds: [0],
+			minutes: [0],
+			hours: [0],
+			days: [1],
+			months: [0],
+			weekdays: [0],
+		})
 	})
 
 	test('Should default to 0 when no seconds are specified in the cron expression', () => {