feat: [435] add support for the 'L' mark

src/constants.ts

@@ -47,7 +47,8 @@ export const ALIASES = Object.freeze({
 	wed: 3,
 	thu: 4,
 	fri: 5,
-	sat: 6
+	sat: 6,
+	l: 'l'
 } as const);
 export const TIME_UNITS_MAP = Object.freeze({
 	SECOND: 'second',
@@ -80,3 +81,4 @@ export const PRESETS = Object.freeze({
 export const RE_WILDCARDS = /\*/g;
 export const RE_RANGE = /^(\d+)(?:-(\d+))?(?:\/(\d+))?$/g;
 export const RE_QUESTIONMARK = /\?/g;
+export const RE_L = /[lL]/g;

src/time.ts

@@ -6,6 +6,7 @@ import {
 	MONTH_CONSTRAINTS,
 	PARSE_DEFAULTS,
 	PRESETS,
+	RE_L,
 	RE_QUESTIONMARK,
 	RE_RANGE,
 	RE_WILDCARDS,
@@ -766,6 +767,9 @@ export class CronTime {
 			}
 		});
 
+		// "L" is a shortcut for the last day of the month
+		value = value.replace(RE_L, this._getLastDayOf(now, unit));
+
 		// "?" will be replaced with current timestamp value
 		value = value.replace(RE_QUESTIONMARK, this._getTimeUnit(now, unit));
 
@@ -852,4 +856,9 @@ export class CronTime {
 				throw new CronError('Invalid time unit');
 		}
 	}
+
+	private _getLastDayOf(now: DateTime, unit: TimeUnit) {
+		if (unit === 'dayOfMonth') return now.endOf('month').day.toString();
+		return '7';
+	}
 }

tests/crontime.test.ts

@@ -350,20 +350,6 @@ describe('crontime', () => {
 		});
 	});
 
-	describe('should throw an exception because `L` not supported', () => {
-		it('(* * * L * *)', () => {
-			expect(() => {
-				new CronTime('* * * L * *');
-			}).toThrow();
-		});
-
-		it('(* * * * * L)', () => {
-			expect(() => {
-				new CronTime('* * * * * L');
-			}).toThrow();
-		});
-	});
-
 	it('should strip off millisecond', () => {
 		const cronTime = new CronTime('0 */10 * * * *');
 		const x = cronTime.getNextDateFrom(new Date('2018-08-10T02:20:00.999Z'));
@@ -843,4 +829,27 @@ describe('crontime', () => {
 			clock.restore();
 		});
 	});
+
+	describe("should support 'L' for last day of the month", () => {
+		it('should substitute last day of the month for "* * L * *"', () => {
+			const clock = sinon.useFakeTimers();
+
+			const now = DateTime.local();
+			const ct = new CronTime('* * L * *');
+			const day = ct.sendAt().get('day');
+			expect(day).toBe(now.endOf('month').get('day'));
+
+			clock.restore();
+		});
+
+		it('should substitute last day of the week for "* * * * * L', () => {
+			const clock = sinon.useFakeTimers();
+
+			const ct = new CronTime('* * * * L');
+			const day = ct.sendAt().get('weekday');
+			expect(day).toBe(7);
+
+			clock.restore();
+		});
+	});
 });