Upgrade to React 18 (#24916)

app/javascript/packs/admin.jsx

@@ -2,7 +2,7 @@ import './public-path';
 import { delegate } from '@rails/ujs';
 import ready from '../mastodon/ready';
 import React from 'react';
-import ReactDOM from 'react-dom';
+import { createRoot } from 'react-dom/client';
 
 const setAnnouncementEndsAttributes = (target) => {
   const valid = target?.value && target?.validity?.valid;
@@ -231,11 +231,13 @@ ready(() => {
 
     import('../mastodon/containers/admin_component').then(({ default: AdminComponent }) => {
       return import('../mastodon/components/admin/' + componentName).then(({ default: Component }) => {
-        ReactDOM.render((
+        const root = createRoot(element);
+
+        root.render (
           <AdminComponent locale={locale}>
             <Component {...componentProps} />
-          </AdminComponent>
-        ), element);
+          </AdminComponent>,
+        );
       });
     }).catch(error => {
       console.error(error);

app/javascript/packs/public.jsx

@@ -15,7 +15,7 @@ import { delegate }  from '@rails/ujs';
 import emojify  from '../mastodon/features/emoji/emoji';
 import { getLocale }  from '../mastodon/locales';
 import React  from 'react';
-import ReactDOM  from 'react-dom';
+import { createRoot }  from 'react-dom/client';
 import { createBrowserHistory }  from 'history';
 
 start();
@@ -153,7 +153,8 @@ function loaded() {
 
           const content = document.createElement('div');
 
-          ReactDOM.render(<MediaContainer locale={locale} components={reactComponents} />, content);
+          const root = createRoot(content);
+          root.render(<MediaContainer locale={locale} components={reactComponents} />);
           document.body.appendChild(content);
           scrollToDetailedStatus();
         })

app/javascript/packs/share.jsx

@@ -4,7 +4,7 @@ import { start } from '../mastodon/common';
 import ready from '../mastodon/ready';
 import ComposeContainer  from '../mastodon/containers/compose_container';
 import React from 'react';
-import ReactDOM from 'react-dom';
+import { createRoot } from 'react-dom/client';
 
 start();
 
@@ -16,7 +16,8 @@ function loaded() {
     if(!attr) return;
 
     const props = JSON.parse(attr);
-    ReactDOM.render(<ComposeContainer {...props} />, mountNode);
+    const root = createRoot(mountNode);
+    root.render(<ComposeContainer {...props} />);
   }
 }