fix: Clear the previously selected date on empty input with showTimeSelectOnly

Previously, the selected date was not being cleared and retained the previously selected time when an empty value was passed to the date input while showTimeSelectOnly was enabled due to a bug.  This commit address the issue and adds test cases to ensure proper functionality.

Closes #4170

Author: Balaji Sridharan

src/index.jsx

@@ -542,21 +542,14 @@ export default class DatePicker extends React.Component {
     if (
       this.props.showTimeSelectOnly &&
       this.props.selected &&
+      date &&
       !isSameDay(date, this.props.selected)
     ) {
-      if (date == null) {
-        date = set(this.props.selected, {
-          hours: getHours(this.props.selected),
-          minutes: getMinutes(this.props.selected),
-          seconds: getSeconds(this.props.selected),
-        });
-      } else {
-        date = set(this.props.selected, {
-          hours: getHours(date),
-          minutes: getMinutes(date),
-          seconds: getSeconds(date),
-        });
-      }
+      date = set(this.props.selected, {
+        hours: getHours(date),
+        minutes: getMinutes(date),
+        seconds: getSeconds(date),
+      });
     }
     if (date || !event.target.value) {
       this.setSelected(date, event, true);

test/datepicker_test.test.js

@@ -4,6 +4,7 @@ import { findDOMNode } from "react-dom";
 import TestUtils from "react-dom/test-utils";
 import { enUS, enGB } from "date-fns/locale";
 import { mount } from "enzyme";
+import { render, fireEvent } from "@testing-library/react";
 import defer from "lodash/defer";
 import DatePicker, { registerLocale } from "../src/index.jsx";
 import Day from "../src/day.jsx";
@@ -2102,6 +2103,55 @@ describe("DatePicker", () => {
     });
   });
 
+  it("clears the selected date on empty date input", () => {
+    let date = "2023-10-23 10:00:00";
+    const selected = utils.newDate(date);
+
+    const { container: datepicker } = render(
+      <DatePicker
+        selected={selected}
+        onChange={(d) => {
+          date = d;
+        }}
+        showTimeSelect
+        dateFormat="MMMM d, yyyy h:mm aa"
+      />,
+    );
+
+    const input = datepicker.querySelector(
+      ".react-datepicker__input-container > input",
+    );
+    fireEvent.change(input, { target: { value: "" } });
+
+    expect(date).toBe(null);
+  });
+
+  it("clears the selected date on empty date input with showTimeSelectOnly", () => {
+    const format = "h:mm aa";
+
+    let date = "2022-02-24 10:00:00";
+    const selected = utils.newDate(date);
+
+    const { container: datepicker } = render(
+      <DatePicker
+        selected={selected}
+        onChange={(d) => {
+          date = d;
+        }}
+        showTimeSelectOnly
+        dateFormat={format}
+        timeFormat={format}
+      />,
+    );
+
+    const input = datepicker.querySelector(
+      ".react-datepicker__input-container > input",
+    );
+    fireEvent.change(input, { target: { value: "" } });
+
+    expect(date).toBe(null);
+  });
+
   it("should selected month when specified minDate same month", () => {
     const selected = utils.newDate("2023-01-09");
     let date = null;