Update to eslint v9 (#3385)

.gitignore

@@ -21,7 +21,8 @@ tmp/*
 /static/
 /.env
 docs/_build
-*venv
+.venv/
+venv/
 /media/
 .cache/
 coverage/

.prettierignore

@@ -4,7 +4,8 @@ coverage/
 docs/_build/
 package-lock.json
 specs/
-?venv/
+.venv/
+venv/
 
 /.github/
 /media/

CONTRIBUTING.rst

@@ -150,7 +150,7 @@ Alternatively, you can format your code using:
     $ make prettier
 
 Additionally, there are linting rules that are defined in our
-``.eslintrc.js`` file. To run the linter, do:
+``eslint.config.mjs`` file. To run the linter, do:
 
 .. code-block:: shell
 

eslint.config.mjs

@@ -0,0 +1,122 @@
+import react from 'eslint-plugin-react';
+import globals from 'globals';
+import eslint from '@eslint/js';
+
+export default [
+  {
+    ignores: [
+      '**/.vscode/',
+      '.github/',
+      'media/',
+      'static/',
+      '**/coverage/',
+      'docs/_build/',
+      '**/package-lock.json',
+      '**/specs/',
+      '**/.venv/',
+      '**/venv/',
+      'translate/dist/',
+      // Jinja templates
+      'translate/public/translate.html',
+      '**/templates/**/*.html',
+      // Vendored code
+      'error_pages/css/blockrain.css',
+      'error_pages/js/',
+      'pontoon/base/static/css/boilerplate.css',
+      'pontoon/base/static/css/fontawesome-all.css',
+      'pontoon/base/static/css/nprogress.css',
+      'pontoon/base/static/js/lib/',
+    ],
+  },
+  eslint.configs.recommended,
+  react.configs.flat.recommended,
+  {
+    plugins: {
+      react,
+    },
+
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        ...globals.jest,
+        gettext: 'readonly',
+        ngettext: 'readonly',
+        interpolate: 'readonly',
+        l: 'readonly',
+        expect: 'readonly',
+        test: 'readonly',
+        browser: 'readonly',
+        jest: 'readonly',
+        Promise: 'readonly',
+        Set: 'readonly',
+        URLSearchParameters: 'readonly',
+        FormData: 'readonly',
+        require: 'readonly',
+        shortcut: 'readonly',
+        sorttable: 'readonly',
+        $: 'readonly',
+        Pontoon: 'readonly',
+        jQuery: 'readonly',
+        Clipboard: 'readonly',
+        Chart: 'readonly',
+        NProgress: 'readonly',
+        diff_match_patch: 'readonly',
+        Highcharts: 'readonly',
+        Sideshow: 'readonly',
+        editor: 'readonly',
+        DIFF_INSERT: 'readonly',
+        DIFF_EQUAL: 'readonly',
+        DIFF_DELETE: 'readonly',
+        ga: 'readonly',
+        process: 'readonly',
+        generalShortcutsHandler: 'writable',
+        traversalShortcutsHandler: 'writable',
+        editorShortcutsHandler: 'writable',
+        showdown: 'writable',
+      },
+
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+    },
+
+    settings: {
+      react: {
+        version: 'detect',
+      },
+    },
+
+    rules: {
+      curly: 'error',
+      'react/display-name': 0,
+      'react/prefer-es6-class': 1,
+      'react/prefer-stateless-function': 0,
+      'react/prop-types': 0,
+      'react/jsx-key': 0,
+      'react/jsx-uses-react': 1,
+      'react/jsx-uses-vars': 1,
+
+      'no-unused-vars': [
+        'error',
+        {
+          vars: 'all',
+          args: 'after-used',
+          ignoreRestSiblings: true,
+        },
+      ],
+
+      'no-console': 1,
+      'no-var': 'error',
+
+      'prefer-const': [
+        'error',
+        {
+          destructuring: 'any',
+          ignoreReadBeforeAssign: false,
+        },
+      ],
+    },
+  },
+];