[MM-50821] Notify about successful login only once via screen reader (#24979)

* [MM-50821] Notify about successful login only once via screen reader

* clear timeout via useEffect instead of inside setTimeout in AdvanceTextEditor

* declare timeout as ref in AdvancedTextEditor

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/channels/src/components/advanced_text_editor/advanced_text_editor.tsx

@@ -2,7 +2,7 @@
 // See LICENSE.txt for license information.
 
 import classNames from 'classnames';
-import React, {useCallback, useEffect, useRef, useState} from 'react';
+import React, {useCallback, useEffect, useMemo, useRef, useState} from 'react';
 import {FormattedMessage, useIntl} from 'react-intl';
 import {useDispatch} from 'react-redux';
 
@@ -13,6 +13,7 @@ import type {ServerError} from '@mattermost/types/errors';
 import type {FileInfo} from '@mattermost/types/files';
 
 import {emitShortcutReactToLastPostFrom} from 'actions/post_actions';
+import LocalStorageStore from 'stores/local_storage_store';
 
 import AutoHeightSwitcher from 'components/common/auto_height_switcher';
 import EmojiPickerOverlay from 'components/emoji_picker/emoji_picker_overlay';
@@ -191,6 +192,7 @@ const AdvanceTextEditor = ({
     const emojiPickerRef = useRef<HTMLButtonElement>(null);
     const editorActionsRef = useRef<HTMLDivElement>(null);
     const editorBodyRef = useRef<HTMLDivElement>(null);
+    const timeout = useRef<NodeJS.Timeout>();
 
     const [renderScrollbar, setRenderScrollbar] = useState(false);
     const [showFormattingSpacer, setShowFormattingSpacer] = useState(shouldShowPreview);
@@ -605,6 +607,29 @@ const AdvanceTextEditor = ({
         }
     }, [handleWidthChange, message]);
 
+    useEffect(() => {
+        return () => timeout.current && clearTimeout(timeout.current);
+    }, []);
+
+    const wasNotifiedOfLogIn = LocalStorageStore.getWasNotifiedOfLogIn();
+
+    const ariaLabel = useMemo(() => {
+        let label;
+        if (!wasNotifiedOfLogIn) {
+            label = Utils.localizeMessage(
+                'channelView.login.successfull',
+                'Login Successful',
+            );
+
+            // set timeout to make sure aria-label is read by a screen reader,
+            // and then set the flag to "true" to make sure it's not read again until a user logs back in
+            timeout.current = setTimeout(() => {
+                LocalStorageStore.setWasNotifiedOfLogIn(true);
+            }, 3000);
+        }
+        return label ? `${label} ${ariaLabelMessageInput}` : ariaLabelMessageInput;
+    }, [ariaLabelMessageInput, wasNotifiedOfLogIn]);
+
     const formattingBar = (
         <AutoHeightSwitcher
             showSlot={showFormattingBar ? 1 : 2}
@@ -632,16 +657,17 @@ const AdvanceTextEditor = ({
                     'formatting-bar': showFormattingBar,
                 })}
             >
-                <div
-                    id={'speak-'}
-                    aria-live='assertive'
-                    className='sr-only'
-                >
-                    <FormattedMessage
-                        id='channelView.login.successfull'
-                        defaultMessage='Login Successfull'
-                    />
-                </div>
+                {!wasNotifiedOfLogIn && (
+                    <div
+                        aria-live='assertive'
+                        className='sr-only'
+                    >
+                        <FormattedMessage
+                            id='channelView.login.successfull'
+                            defaultMessage='Login Successful'
+                        />
+                    </div>
+                )}
                 <div
                     className={'AdvancedTextEditor__body'}
                     disabled={readOnlyChannel}
@@ -651,10 +677,7 @@ const AdvanceTextEditor = ({
                         role='application'
                         id='advancedTextEditorCell'
                         data-a11y-sort-order='2'
-                        aria-label={Utils.localizeMessage(
-                            'channelView.login.successfull',
-                            'Login Successfull',
-                        ) + ' ' + ariaLabelMessageInput}
+                        aria-label={ariaLabel}
                         tabIndex={-1}
                         className='AdvancedTextEditor__cell a11y__region'
                     >

webapp/channels/src/components/login/login.tsx

@@ -659,6 +659,11 @@ const Login = ({onCustomizeHeader}: LoginProps) => {
         // Record a successful login to local storage. If an unintentional logout occurs, e.g.
         // via session expiration, this bit won't get reset and we can notify the user as such.
         LocalStorageStore.setWasLoggedIn(true);
+
+        // After a user has just logged in, we set the following flag to "false" so that after
+        // a user is notified of successful login, we can set it back to "true"
+        LocalStorageStore.setWasNotifiedOfLogIn(false);
+
         if (redirectTo && redirectTo.match(/^\/([^/]|$)/)) {
             history.push(redirectTo);
         } else if (team) {

webapp/channels/src/stores/local_storage_store.ts

@@ -16,6 +16,7 @@ export const getPenultimateChannelNameKey = (userId: string, teamId: string) =>
 const getRecentEmojisKey = (userId: string) => ['recent_emojis', userId].join(':');
 const getWasLoggedInKey = () => 'was_logged_in';
 const teamIdJoinedOnLoadKey = 'teamIdJoinedOnLoad';
+const wasNotifiedOfLogInKey = 'was_notified_of_login';
 
 const getPathScopedKey = (path: string, key: string) => {
     if (path === '' || path === '/') {
@@ -156,6 +157,16 @@ class LocalStorageStoreClass {
     getWasLoggedIn() {
         return this.getItem(getWasLoggedInKey()) === 'true';
     }
+
+    // the following flag's setter and getter are used to make sure a user is notified (via aria-label)
+    // about a successful login only once (MM-50821)
+    setWasNotifiedOfLogIn(wasNotified: boolean) {
+        this.setItem(wasNotifiedOfLogInKey, String(wasNotified));
+    }
+
+    getWasNotifiedOfLogIn() {
+        return this.getItem(wasNotifiedOfLogInKey) === 'true';
+    }
 }
 
 const LocalStorageStore = new LocalStorageStoreClass();