fix(datetime): switching month and year accounts for day (#25996)

resolves #25585

core/src/components/datetime/datetime.tsx

@@ -45,6 +45,7 @@ import {
   getPreviousWeek,
   getPreviousYear,
   getStartOfWeek,
+  validateParts,
 } from './utils/manipulation';
 import {
   clampDate,
@@ -583,6 +584,19 @@ export class Datetime implements ComponentInterface {
   private setActiveParts = (parts: DatetimeParts, removeDate = false) => {
     const { multiple, activePartsClone, highlightActiveParts } = this;
 
+    /**
+     * When setting the active parts, it is possible
+     * to set invalid data. For example,
+     * when updating January 31 to February,
+     * February 31 does not exist. As a result
+     * we need to validate the active parts and
+     * ensure that we are only setting valid dates.
+     * Additionally, we need to update the working parts
+     * too in the event that the validated parts are different.
+     */
+    const validatedParts = validateParts(parts);
+    this.setWorkingParts(validatedParts);
+
     if (multiple) {
       /**
        * We read from activePartsClone here because valueChanged() only updates that,
@@ -595,20 +609,20 @@ export class Datetime implements ComponentInterface {
        */
       const activePartsArray = Array.isArray(activePartsClone) ? activePartsClone : [activePartsClone];
       if (removeDate) {
-        this.activeParts = activePartsArray.filter((p) => !isSameDay(p, parts));
+        this.activeParts = activePartsArray.filter((p) => !isSameDay(p, validatedParts));
       } else if (highlightActiveParts) {
-        this.activeParts = [...activePartsArray, parts];
+        this.activeParts = [...activePartsArray, validatedParts];
       } else {
         /**
          * If highlightActiveParts is false, that means we just have a
          * default value of today in activeParts; we need to replace that
          * rather than adding to it since it's just a placeholder.
          */
-        this.activeParts = [parts];
+        this.activeParts = [validatedParts];
       }
     } else {
       this.activeParts = {
-        ...parts,
+        ...validatedParts,
       };
     }
 

core/src/components/datetime/test/datetime.e2e.ts

@@ -0,0 +1,48 @@
+import { expect } from '@playwright/test';
+import { test } from '@utils/test/playwright';
+
+test.describe('datetime: switching months with different number of days', () => {
+  test.beforeEach(async ({ page, skip }) => {
+    skip.rtl();
+    skip.mode('ios');
+
+    await page.setContent(`
+      <ion-datetime locale="en-US" presentation="date" value="2022-01-31"></ion-datetime>
+    `);
+
+    await page.waitForSelector('.datetime-ready');
+  });
+
+  test('should switch the calendar header when moving to a month with a different number of days', async ({ page }) => {
+    const monthYearToggle = page.locator('ion-datetime .calendar-month-year');
+    const monthColumnItems = page.locator('ion-datetime .month-column .picker-item:not(.picker-item-empty)');
+
+    await expect(monthYearToggle).toContainText('January 2022');
+
+    await monthYearToggle.click();
+    await page.waitForChanges();
+
+    // February
+    await monthColumnItems.nth(1).click();
+    await page.waitForChanges();
+
+    await expect(monthYearToggle).toContainText('February 2022');
+  });
+
+  test('should adjust the selected day when moving to a month with a different number of days', async ({ page }) => {
+    const monthYearToggle = page.locator('ion-datetime .calendar-month-year');
+    const monthColumnItems = page.locator('ion-datetime .month-column .picker-item:not(.picker-item-empty)');
+    const datetime = page.locator('ion-datetime');
+    const ionChange = await page.spyOnEvent('ionChange');
+
+    await monthYearToggle.click();
+    await page.waitForChanges();
+
+    // February
+    await monthColumnItems.nth(1).click();
+
+    await ionChange.next();
+    await expect(ionChange).toHaveReceivedEventTimes(1);
+    await expect(datetime).toHaveJSProperty('value', '2022-02-28');
+  });
+});

core/src/components/datetime/utils/manipulation.ts

@@ -339,3 +339,27 @@ export const calculateHourFromAMPM = (currentParts: DatetimeParts, newAMPM: 'am'
 
   return newHour;
 };
+
+/**
+ * Updates parts to ensure that month and day
+ * values are valid. For days that do not exist,
+ * the closest valid day is used.
+ */
+export const validateParts = (parts: DatetimeParts): DatetimeParts => {
+  const { month, day, year } = parts;
+  const partsCopy = { ...parts };
+
+  const numDays = getNumDaysInMonth(month, year);
+
+  /**
+   * If the max number of days
+   * is greater than the day we want
+   * to set, update the DatetimeParts
+   * day field to be the max days.
+   */
+  if (day !== null && numDays < day) {
+    partsCopy.day = numDays;
+  }
+
+  return partsCopy;
+};