fix(datetime): update active calendar display when value changes

core/src/components/datetime/datetime.tsx

@@ -93,6 +93,12 @@ export class Datetime implements ComponentInterface {
   private minParts?: any;
   private maxParts?: any;
 
+  /**
+   * Duplicate reference to `activeParts` that does not trigger a re-render of the component.
+   * Allows caching an instance of the `activeParts` in between render cycles.
+   */
+  private activePartsClone!: DatetimeParts;
+
   @State() showMonthAndYear = false;
 
   @State() activeParts: DatetimeParts = {
@@ -291,6 +297,25 @@ export class Datetime implements ComponentInterface {
    */
   @Watch('value')
   protected valueChanged() {
+    if (this.hasValue()) {
+      /**
+       * Clones the value of the `activeParts` to the private clone, to update
+       * the date display on the current render cycle without causing another render.
+       *
+       * This allows us to update the current value's date/time display without
+       * refocusing or shifting the user's display (leaves the user in place).
+       */
+      const { month, day, year, hour, minute } = parseDate(this.value);
+      this.activePartsClone = {
+        ...this.activeParts,
+        month,
+        day,
+        year,
+        hour,
+        minute
+      }
+    }
+
     this.emitStyle();
     this.ionChange.emit({
       value: this.value
@@ -911,7 +936,8 @@ export class Datetime implements ComponentInterface {
       tzOffset,
       ampm: hour >= 12 ? 'pm' : 'am'
     }
-    this.activeParts = {
+
+    this.activePartsClone = this.activeParts = {
       month,
       day,
       year,
@@ -951,6 +977,10 @@ export class Datetime implements ComponentInterface {
     this.ionBlur.emit();
   }
 
+  private hasValue = () => {
+    return this.value != null && this.value !== '';
+  }
+
   private nextMonth = () => {
     const { calendarBodyRef } = this;
     if (!calendarBodyRef) { return; }
@@ -1135,7 +1165,7 @@ export class Datetime implements ComponentInterface {
           {getDaysOfMonth(month, year, this.firstDayOfWeek % 7).map((dateObject, index) => {
             const { day, dayOfWeek } = dateObject;
             const referenceParts = { month, day, year };
-            const { isActive, isToday, ariaLabel, ariaSelected, disabled } = getCalendarDayState(this.locale, referenceParts, this.activeParts, this.todayParts, this.minParts, this.maxParts, this.parsedDayValues);
+            const { isActive, isToday, ariaLabel, ariaSelected, disabled } = getCalendarDayState(this.locale, referenceParts, this.activePartsClone, this.todayParts, this.minParts, this.maxParts, this.parsedDayValues);
 
             return (
               <button
@@ -1213,21 +1243,22 @@ export class Datetime implements ComponentInterface {
     ampmItems: PickerColumnItem[],
     use24Hour: boolean
    ) {
-    const { color, workingParts } = this;
+    const { color, activePartsClone, workingParts } = this;
+
     return (
       <ion-picker-internal>
         <ion-picker-column-internal
           color={color}
-          value={workingParts.hour}
+          value={activePartsClone.hour}
           items={hoursItems}
           numericInput
           onIonChange={(ev: CustomEvent) => {
             this.setWorkingParts({
-              ...this.workingParts,
+              ...workingParts,
               hour: ev.detail.value
             });
             this.setActiveParts({
-              ...this.activeParts,
+              ...activePartsClone,
               hour: ev.detail.value
             });
 
@@ -1236,16 +1267,16 @@ export class Datetime implements ComponentInterface {
         ></ion-picker-column-internal>
         <ion-picker-column-internal
           color={color}
-          value={workingParts.minute}
+          value={activePartsClone.minute}
           items={minutesItems}
           numericInput
           onIonChange={(ev: CustomEvent) => {
             this.setWorkingParts({
-              ...this.workingParts,
+              ...workingParts,
               minute: ev.detail.value
             });
             this.setActiveParts({
-              ...this.activeParts,
+              ...activePartsClone,
               minute: ev.detail.value
             });
 
@@ -1254,19 +1285,19 @@ export class Datetime implements ComponentInterface {
         ></ion-picker-column-internal>
         { !use24Hour && <ion-picker-column-internal
           color={color}
-          value={workingParts.ampm}
+          value={activePartsClone.ampm}
           items={ampmItems}
           onIonChange={(ev: CustomEvent) => {
-            const hour = calculateHourFromAMPM(this.workingParts, ev.detail.value);
+            const hour = calculateHourFromAMPM(workingParts, ev.detail.value);
 
             this.setWorkingParts({
-              ...this.workingParts,
+              ...workingParts,
               ampm: ev.detail.value,
               hour
             });
 
             this.setActiveParts({
-              ...this.workingParts,
+              ...activePartsClone,
               ampm: ev.detail.value,
               hour
             });
@@ -1309,7 +1340,7 @@ export class Datetime implements ComponentInterface {
           }
         }}
       >
-        {getFormattedTime(this.workingParts, use24Hour)}
+        {getFormattedTime(this.activePartsClone, use24Hour)}
       </button>,
       <ion-popover
         alignment="center"

core/src/components/datetime/test/set-value/e2e.ts

@@ -0,0 +1,37 @@
+import { newE2EPage } from '@stencil/core/testing';
+
+describe('datetime: setting the value', () => {
+
+  it('should update the active date', async () => {
+    const page = await newE2EPage({
+      url: '/src/components/datetime/test/set-value?ionic:_testing=true'
+    });
+
+    await page.$eval('ion-datetime', (elm: any) => {
+      elm.value = '2021-11-25T12:40:00.000Z';
+    });
+
+    await page.waitForChanges();
+
+    const activeDate = await page.find('ion-datetime >>> .calendar-day-active');
+
+    expect(activeDate).toEqualText('25');
+  });
+
+  it('should update the active time', async () => {
+    const page = await newE2EPage({
+      url: '/src/components/datetime/test/set-value?ionic:_testing=true'
+    });
+
+    await page.$eval('ion-datetime', (elm: any) => {
+      elm.value = '2021-11-25T12:40:00.000Z';
+    });
+
+    await page.waitForChanges();
+
+    const activeTime = await page.find('ion-datetime >>> .time-body');
+
+    expect(activeTime).toEqualText('12:40 PM');
+  })
+})
+

core/src/components/datetime/test/set-value/index.html

@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<html lang="en" dir="ltr">
+
+<head>
+  <meta charset="UTF-8">
+  <title>Datetime - Set Value</title>
+  <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
+  <link href="../../../../../css/ionic.bundle.css" rel="stylesheet">
+  <link href="../../../../../scripts/testing/styles.css" rel="stylesheet">
+  <script src="../../../../../scripts/testing/scripts.js"></script>
+  <script type="module" src="../../../../../dist/ionic/ionic.esm.js"></script>
+  <style>
+    h2 {
+      font-size: 12px;
+      font-weight: normal;
+
+      color: #6f7378;
+
+      margin-top: 10px;
+      margin-left: 5px;
+    }
+
+    ion-datetime {
+      width: 350px;
+    }
+  </style>
+</head>
+
+<body>
+  <ion-app>
+    <ion-header translucent="true">
+      <ion-toolbar>
+        <ion-title>Datetime - Set Value</ion-title>
+      </ion-toolbar>
+    </ion-header>
+    <ion-content class="ion-padding">
+      <ion-datetime value="2021-11-22T14:23:00.000Z" locale="en-US"></ion-datetime>
+    </ion-content>
+  </ion-app>
+</body>
+
+</html>

core/src/components/picker-column-internal/picker-column-internal.tsx

@@ -24,6 +24,7 @@ import { PickerColumnItem } from './picker-column-internal-interfaces';
 export class PickerColumnInternal implements ComponentInterface {
   private destroyScrollListener?: () => void;
   private hapticsStarted = false;
+  private isColumnVisible = false;
 
   @State() isActive = false;
 
@@ -64,12 +65,18 @@ export class PickerColumnInternal implements ComponentInterface {
 
   @Watch('value')
   valueChange() {
-    const { items, value } = this;
-    this.scrollActiveItemIntoView();
+    if (this.isColumnVisible) {
+      /**
+       * Only scroll the active item into view and emit the value
+       * change, when the picker column is actively visible to the user.
+       */
+      const { items, value } = this;
+      this.scrollActiveItemIntoView();
 
-    const findItem = items.find(item => item.value === value);
-    if (findItem) {
-      this.ionChange.emit(findItem);
+      const findItem = items.find(item => item.value === value);
+      if (findItem) {
+        this.ionChange.emit(findItem);
+      }
     }
   }
 
@@ -86,11 +93,13 @@ export class PickerColumnInternal implements ComponentInterface {
       if (ev.isIntersecting) {
         this.scrollActiveItemIntoView();
         this.initializeScrollListener();
+        this.isColumnVisible = true;
       } else {
         if (this.destroyScrollListener) {
           this.destroyScrollListener();
           this.destroyScrollListener = undefined;
         }
+        this.isColumnVisible = false;
       }
     }
     new IntersectionObserver(visibleCallback, { threshold: 0.01 }).observe(this.el);