fix: convertToDate correctly parses time string portions

Added tests for date-time input. The date utilities
class uses the new parse ISO implementation which
returns `null` instead of `Invalid date` for certain
time portions. Adjusted the tests accordingly.
This means that the date-time input additional checks around
the mask value logic could be simplified but that is for
another PR.

Author: rkaraivanov

src/components/calendar/helpers.ts

@@ -37,6 +37,24 @@ const DaysMap = {
 
 /* Converter functions */
 
+export function isValidDate(date: Date) {
+  return Number.isNaN(date.valueOf()) ? null : date;
+}
+
+export function parseISODate(string: string) {
+  if (/^\d{4}/.test(string)) {
+    const time = !string.includes('T') ? 'T00:00:00' : '';
+    return isValidDate(new Date(`${string}${time}`));
+  }
+
+  if (/^\d{2}/.test(string)) {
+    const date = first(new Date().toISOString().split('T'));
+    return isValidDate(new Date(`${date}T${string}`));
+  }
+
+  return null;
+}
+
 /**
  * Converts the given value to a Date object.
  *
@@ -50,8 +68,7 @@ export function convertToDate(value?: Date | string | null): Date | null {
     return null;
   }
 
-  const converted = isString(value) ? new Date(value) : value;
-  return Number.isNaN(converted.valueOf()) ? null : converted;
+  return isString(value) ? parseISODate(value) : isValidDate(value);
 }
 
 /**

src/components/date-picker/date-picker.spec.ts

@@ -286,7 +286,7 @@ describe('Date picker', () => {
     it('should set the value trough attribute correctly', async () => {
       expect(picker.value).to.be.null;
       const expectedValue = new CalendarDay({ year: 2024, month: 2, date: 1 });
-      picker.setAttribute('value', expectedValue.native.toDateString());
+      picker.setAttribute('value', expectedValue.native.toISOString());
       await elementUpdated(picker);
 
       checkDatesEqual(picker.value!, expectedValue);

src/components/date-time-input/date-time-input.spec.ts

@@ -269,6 +269,23 @@ describe('Date Time Input component', () => {
       expect(el.value).to.equal(value);
     });
 
+    it('set value - time portion only', async () => {
+      const target = new Date();
+      target.setHours(14, 0, 0, 0);
+
+      el.inputFormat = 'HH:mm';
+      el.value = '14:00';
+      await elementUpdated(el);
+
+      expect(el.value?.valueOf()).to.equal(target.valueOf());
+
+      // Invalid time portion
+      el.value = '23:60';
+      await elementUpdated(el);
+
+      expect(el.value).to.be.null;
+    });
+
     it('set value - string property binding', async () => {
       const value = new Date(2020, 2, 3);
       el.value = value.toISOString();

src/components/date-time-input/date-util.spec.ts

@@ -177,10 +177,8 @@ describe('Date Util', () => {
       updateDate(new Date(), '11:11').getTime()
     );
 
+    expect(DateTimeUtil.parseIsoDate('23:60')).to.be.null;
     expect(DateTimeUtil.parseIsoDate('')).to.be.null;
-    expect(
-      DateTimeUtil.parseIsoDate(new Date().getTime().toString())?.getTime()
-    ).to.be.NaN;
   });
 
   it('isValidDate should properly determine if a date is valid or not', () => {

src/components/date-time-input/date-util.ts

@@ -1,3 +1,4 @@
+import { parseISODate } from '../calendar/helpers.js';
 import { MaskParser } from '../mask-input/mask-parser.js';
 
 export enum FormatDesc {
@@ -190,22 +191,7 @@ export abstract class DateTimeUtil {
   }
 
   public static parseIsoDate(value: string): Date | null {
-    let regex = /^\d{4}/g;
-    const timeLiteral = 'T';
-    if (regex.test(value)) {
-      return new Date(
-        `${value}${value.indexOf(timeLiteral) === -1 ? 'T00:00:00' : ''}`
-      );
-    }
-
-    regex = /^\d{2}/g;
-    if (regex.test(value)) {
-      const dateNow = new Date().toISOString();
-      const [datePart, _timePart] = dateNow.split(timeLiteral);
-      return new Date(`${datePart}T${value}`);
-    }
-
-    return null;
+    return parseISODate(value);
   }
 
   public static isValidDate(value: any): value is Date {