Clean up fix of recurring tasks without a date

Added new test file for recurrence.

src/Recurrence.ts

@@ -21,7 +21,7 @@ export class Recurrence {
      * same relative distance to the due date as the original task. For example
      * "starts one week before it is due".
      */
-    private readonly referenceDate: Moment;
+    private readonly referenceDate: Moment | null;
 
     constructor({
         rrule,
@@ -33,7 +33,7 @@ export class Recurrence {
     }: {
         rrule: RRule;
         baseOnToday: boolean;
-        referenceDate: Moment;
+        referenceDate: Moment | null;
         startDate: Moment | null;
         scheduledDate: Moment | null;
         dueDate: Moment | null;
@@ -80,11 +80,9 @@ export class Recurrence {
                     referenceDate = window.moment(scheduledDate);
                 } else if (startDate) {
                     referenceDate = window.moment(startDate);
-                } else {
-                    referenceDate = window.moment();
                 }
 
-                if (!baseOnToday) {
+                if (!baseOnToday && referenceDate !== null) {
                     options.dtstart = window
                         .moment(referenceDate)
                         .startOf('day')
@@ -148,7 +146,9 @@ export class Recurrence {
             // date if possible. Otherwise, base it on today if we do not have a
             // reference date.
             const after = window
-                .moment(this.referenceDate) // Can be `null` to mean "today".
+                // Reference date can be `null` to mean "today".
+                // Moment only accepts `undefined`, not `null`.
+                .moment(this.referenceDate ?? undefined)
                 .endOf('day')
                 .utc(true);
 

tests/Recurrence.test.ts

@@ -0,0 +1,30 @@
+/**
+ * @jest-environment jsdom
+ */
+import moment from 'moment';
+import { Recurrence } from '../src/Recurrence';
+
+jest.mock('obsidian');
+window.moment = moment;
+
+describe('Recurrence', () => {
+    it('creates a recurring instance even if no date is given', () => {
+        // Arrange
+        const recurrence = Recurrence.fromText({
+            recurrenceRuleText: 'every week',
+            startDate: null,
+            scheduledDate: null,
+            dueDate: null,
+        });
+
+        // Act
+        const next = recurrence!.next();
+
+        // Assert
+        expect(next).toStrictEqual({
+            startDate: null,
+            scheduledDate: null,
+            dueDate: null,
+        });
+    });
+});

tests/Task.test.ts

@@ -361,9 +361,6 @@ describe('toggle done', () => {
             nextScheduled: '2021-10-18',
             nextDue: '2021-10-20',
         },
-        {
-            interval: 'every week',
-        },
     ];
 
     test.concurrent.each<RecurrenceCase>(recurrenceCases)(