fix(a11y): set #online_count aria-label on init (#7777 CI fix)

The Playwright spec added in 987bb3a failed because aria-label was null
on first paint. updateNumberOfOnlineUsers — which writes the localized
aria-label — only fires on userJoin / userLeave / status change. On a
solo-author pad those events never arrive, so the badge shipped to AT
with no accessible name (and no PR-fail-safe net since pad_mode.ts's
similar pattern also relies on a later event firing).

Call self.updateNumberOfOnlineUsers() at the end of init() once the
DOM node exists, so the initial badge digit ships with its label.

Refs #7255

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: JohnMcLear

src/static/js/pad_userlist.ts

@@ -355,12 +355,17 @@ const paduserlist = (() => {
 
       if ($('#online_count').length === 0) {
         // role="status" + aria-live="polite" announces the count when it
-        // changes; the localized aria-label (set in updateNumberOfOnlineUsers)
-        // turns the bare badge digit into "N connected users" so AT users
-        // get context, not a stray "5". See ether/etherpad#7255.
+        // changes; the localized aria-label (set by updateNumberOfOnlineUsers
+        // below) turns the bare badge digit into "N connected users" so AT
+        // users get context, not a stray "5". See ether/etherpad#7255.
         $('#editbar [data-key=showusers] > a').append(
             '<span id="online_count" role="status" aria-live="polite">1</span>');
       }
+      // Set the initial aria-label. updateNumberOfOnlineUsers otherwise only
+      // fires on userJoin / userLeave / status change — on a solo-author pad
+      // those events never come, and the badge would ship to AT with no
+      // accessible name (the regression Playwright caught on PR #7777).
+      self.updateNumberOfOnlineUsers();
 
       $('#otheruserstable tr').remove();
 

src/tests/frontend-new/specs/a11y_dialogs.spec.ts

@@ -205,14 +205,13 @@ test('online_count badge has a localized accessible label (#7255)', async ({page
   const badge = page.locator('#online_count');
   await expect(badge).toHaveAttribute('role', 'status');
   await expect(badge).toHaveAttribute('aria-live', 'polite');
-  // toHaveText polls so the assertion survives the initial userlist update
-  // that pad_userlist.ts schedules after the connection completes.
+  // toHaveText / toHaveAttribute poll so the assertions survive the
+  // initial userlist init() pass (which appends the span and then sets
+  // its aria-label asynchronously after html10n + setMyUserInfo land).
   await expect(badge).toHaveText(/^\d+$/);
-  const label = await badge.getAttribute('aria-label');
-  expect(label).toBeTruthy();
   // English plural form contains "connected user" — covers both singular
   // and plural without baking the exact count into the test.
-  expect(label).toMatch(/connected user/);
+  await expect(badge).toHaveAttribute('aria-label', /connected user/);
 });
 
 test('linemetricsdiv is hidden from screen readers (#7255)', async ({page}) => {