Upgrade to ESLint v9 flat config (#34324)

Co-authored-by: Nick Schonning <nschonni@gmail.com>

app/javascript/entrypoints/public.tsx

@@ -68,7 +68,7 @@ function loaded() {
 
     if (id) message = localeData[id];
 
-    if (!message) message = defaultMessage as string;
+    message ??= defaultMessage as string;
 
     const messageFormat = new IntlMessageFormat(message, locale);
     return messageFormat.format(values) as string;

app/javascript/mastodon/components/counters.tsx

@@ -1,4 +1,4 @@
-import React from 'react';
+import type React from 'react';
 
 import { FormattedMessage } from 'react-intl';
 

app/javascript/mastodon/components/router.tsx

@@ -1,5 +1,5 @@
 import type { PropsWithChildren } from 'react';
-import React from 'react';
+import type React from 'react';
 
 import { Router as OriginalRouter, useHistory } from 'react-router';
 

app/javascript/mastodon/features/emoji/emoji_compressed.js

@@ -1,5 +1,3 @@
-/* eslint-disable import/no-commonjs --
-   We need to use CommonJS here due to preval */
 // @preval
 // http://www.unicode.org/Public/emoji/5.0/emoji-test.txt
 // This file contains the compressed version of the emoji data from

app/javascript/mastodon/features/emoji/emoji_unicode_mapping_light.ts

@@ -33,11 +33,8 @@ function processEmojiMapData(
   shortCode?: ShortCodesToEmojiDataKey,
 ) {
   const [native, _filename] = emojiMapData;
-  let filename = emojiMapData[1];
-  if (!filename) {
-    // filename name can be derived from unicodeToFilename
-    filename = unicodeToFilename(native);
-  }
+  // filename name can be derived from unicodeToFilename
+  const filename = emojiMapData[1] ?? unicodeToFilename(native);
   unicodeMapping[native] = {
     shortCode,
     filename,

app/javascript/mastodon/features/emoji/unicode_to_filename.js

@@ -1,6 +1,3 @@
-/* eslint-disable import/no-commonjs --
-   We need to use CommonJS here as its imported into a preval file (`emoji_compressed.js`) */
-
 // taken from:
 // https://github.com/twitter/twemoji/blob/47732c7/twemoji-generator.js#L848-L866
 exports.unicodeToFilename = (str) => {

app/javascript/mastodon/features/emoji/unicode_to_unified_name.js

@@ -1,6 +1,3 @@
-/* eslint-disable import/no-commonjs --
-   We need to use CommonJS here as its imported into a preval file (`emoji_compressed.js`) */
-
 function padLeft(str, num) {
   while (str.length < num) {
     str = '0' + str;

app/javascript/mastodon/service_worker/web_push_locales.js

@@ -1,6 +1,3 @@
-/* eslint-disable import/no-commonjs --
-   We need to use CommonJS here as its imported into a preval file (`emoji_compressed.js`) */
-
 /* @preval */
 
 const fs   = require('fs');