Set milliseconds to 0 before returning schedule (fixes #363) (#368)

* test: add failing tests

* fix: set milliseconds to 0 before returning schedule

* refactor: only set milliseconds to 0 if they're not already

* perf: remove redundant setMilliseconds call

Author: sheerlox

src/CronExpression.ts

@@ -396,14 +396,15 @@ export class CronExpression {
       if (startTimestamp === currentDate.getTime()) {
         if (dateMathVerb === 'Add' || currentDate.getMilliseconds() === 0) {
           currentDate.applyDateOperation(dateMathVerb, TimeUnit.Second, this.#fields.hour.values.length);
-        } else {
-          currentDate.setMilliseconds(0);
         }
         continue;
       }
       break;
     }
 
+    if (currentDate.getMilliseconds() !== 0) {
+      currentDate.setMilliseconds(0);
+    }
     this.#currentDate = currentDate;
     return currentDate;
   }

tests/CronExpression.test.ts

@@ -84,6 +84,22 @@ describe('CronExpression', () => {
     expect(cronExpression.toString()).toBe('0 0 0 1 1 0');
   });
 
+  test('should set milliseconds to 0 on next scheduled date (issue #363)', () => {
+    const cronExpression = CronExpressionParser.parse('* * * * *', {
+      currentDate: '2020-03-06T10:02:01.002Z',
+    });
+    const nextDate = cronExpression.next();
+    expect(nextDate.toISOString()).toBe('2020-03-06T10:03:00.000Z');
+  });
+
+  test('should set milliseconds to 0 on previous scheduled date (issue #363)', () => {
+    const cronExpression = CronExpressionParser.parse('* * * * *', {
+      currentDate: '2020-03-06T10:02:01.002Z',
+    });
+    const prevDate = cronExpression.prev();
+    expect(prevDate.toISOString()).toBe('2020-03-06T10:02:00.000Z');
+  });
+
   describe('stringify', () => {
     test('stringify cron expression all stars no seconds 0 * * * * *', () => {
       const expected = '0 * * * * *';