Don't drop scheduled when it's the only date.

Author: chmac

src/Task/Occurrence.ts

@@ -99,8 +99,15 @@ export class Occurrence {
             });
         }
 
+        const hasStartDate = this.startDate !== null;
+        const hasDueDate = this.dueDate !== null;
+        const canDropScheduledDate = hasStartDate || hasDueDate;
+        const shouldDropScheduledDate = dropScheduledDate && canDropScheduledDate;
+
         const startDate = this.nextOccurrenceDate(this.startDate, nextReferenceDate);
-        const scheduledDate = dropScheduledDate ? null : this.nextOccurrenceDate(this.scheduledDate, nextReferenceDate);
+        const scheduledDate = shouldDropScheduledDate
+            ? null
+            : this.nextOccurrenceDate(this.scheduledDate, nextReferenceDate);
         const dueDate = this.nextOccurrenceDate(this.dueDate, nextReferenceDate);
 
         return new Occurrence({

tests/Task/Recurrence.test.ts

@@ -247,4 +247,20 @@ describe('Recurrence - with dropScheduledDateOnRecurrence', () => {
         // Assert
         expect(next!.scheduledDate).toBeNull();
     });
+
+    it('does not drop the scheduledDate when it is the only date', () => {
+        // Arrange
+        const recurrence = Recurrence.fromText({
+            recurrenceRuleText: 'every month',
+            occurrence: new Occurrence({
+                scheduledDate: moment('2022-01-04').startOf('day'),
+            }),
+        });
+
+        // Act
+        const next = recurrence!.next(undefined, true);
+
+        // Assert
+        expect(next!.scheduledDate).not.toBeNull();
+    });
 });