Upgrade to ESLint 9 with flat config format

.github/dependabot.yml

@@ -10,8 +10,6 @@ updates:
     schedule:
       interval: 'monthly'
     ignore:
-      # Needs more work.
-      - dependency-name: 'eslint*'
       - dependency-name: '@elastic/elasticsearch'
       # Needs Node >= 20.15, update when we get there.
       - dependency-name: '@types/node'

eslint.config.js

@@ -0,0 +1,163 @@
+const eslint = require('@eslint/js');
+const eslintConfigPrettier = require('eslint-config-prettier');
+const eslintPluginImport = require('eslint-plugin-import');
+const eslintPluginJest = require('eslint-plugin-jest');
+const eslintPluginPrettier = require('eslint-plugin-prettier');
+const globals = require('globals');
+const tseslint = require('typescript-eslint');
+
+const sharedRules = {
+  'eol-last': 'error',
+  'import/order': [
+    'warn',
+    {
+      groups: [
+        ['builtin', 'external'],
+        ['internal', 'sibling', 'parent', 'index'],
+      ],
+      pathGroups: [
+        {
+          pattern: '@weco/**',
+          group: 'external',
+          position: 'after',
+        },
+      ],
+      pathGroupsExcludedImportTypes: ['builtin', 'object'],
+      alphabetize: {
+        order: 'asc',
+        caseInsensitive: true,
+      },
+      'newlines-between': 'always',
+    },
+  ],
+  'no-mixed-operators': 'warn',
+  'no-multi-spaces': 'warn',
+  'no-multi-str': 'off',
+  'no-restricted-imports': [
+    'error',
+    { patterns: ['../*'] }, // Should only import relatively from same directory
+  ],
+  'no-restricted-syntax': [
+    'error',
+    "JSXElement.children > [expression.callee.property.name='stringify']",
+  ],
+  'no-return-assign': 'off',
+  'prettier/prettier': 'error',
+  'sort-imports': [
+    'error',
+    {
+      ignoreCase: true,
+      ignoreDeclarationSort: true,
+    },
+  ],
+};
+
+module.exports = [
+  // Global ignores
+  {
+    ignores: [
+      '**/node_modules/',
+      '**/libs/',
+      '**/lib/',
+      '**/_next/',
+      '**/dist/',
+      '**/.terraform/',
+    ],
+  },
+  // Global linter options
+  {
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error',
+    },
+  },
+  // Base config for JS files
+  {
+    files: ['**/*.js'],
+    languageOptions: {
+      ecmaVersion: 'latest',
+      sourceType: 'module',
+      parser: require('@babel/eslint-parser'),
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+        requireConfigFile: false,
+      },
+      globals: {
+        ...globals.node,
+        ...globals.jest,
+      },
+    },
+    plugins: {
+      import: eslintPluginImport,
+      jest: eslintPluginJest,
+      prettier: eslintPluginPrettier,
+    },
+    rules: {
+      ...eslint.configs.recommended.rules,
+      ...sharedRules,
+    },
+  },
+  // TypeScript config
+  ...tseslint.configs.recommended.map(config => ({
+    ...config,
+    files: ['**/*.ts'],
+  })),
+  {
+    files: ['**/*.ts'],
+    languageOptions: {
+      parser: tseslint.parser,
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+      globals: {
+        ...globals.node,
+        ...globals.jest,
+      },
+    },
+    plugins: {
+      '@typescript-eslint': tseslint.plugin,
+      import: eslintPluginImport,
+      jest: eslintPluginJest,
+      prettier: eslintPluginPrettier,
+    },
+    rules: {
+      ...sharedRules,
+      'no-use-before-define': 'off',
+      '@typescript-eslint/array-type': ['error'],
+      '@typescript-eslint/no-use-before-define': [
+        'error',
+        { functions: false },
+      ],
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        { ignoreRestSiblings: true },
+      ],
+      'jest/no-standalone-expect': [
+        'error',
+        { additionalTestBlockFunctions: ['each.test'] },
+      ],
+    },
+  },
+  // Jest test files
+  {
+    files: ['**/*test.ts'],
+    plugins: {
+      jest: eslintPluginJest,
+    },
+    rules: {
+      ...eslintPluginJest.configs.recommended.rules,
+    },
+  },
+  // Webhook directory - disable restricted imports
+  {
+    files: ['webhook/**'],
+    rules: {
+      'no-restricted-imports': 'off',
+    },
+  },
+  // Prettier config (should be last)
+  eslintConfigPrettier,
+];

infrastructure/prismic-snapshots/lambda/prismic-backup-trigger.js

@@ -186,7 +186,7 @@ async function prepareAssetsForDownload() {
           url: urlObj.toString(),
           filename,
         };
-      } catch (e) {
+      } catch {
         // If URL parsing fails for any reason, fall back to the original URL
         return {
           id: asset.id,

package.json

@@ -22,22 +22,21 @@
   },
   "devDependencies": {
     "@babel/eslint-parser": "^7.28.5",
+    "@eslint/js": "^9.39.2",
     "@tsconfig/node20": "20.1.8",
     "@typescript-eslint/eslint-plugin": "^8.51.0",
     "@typescript-eslint/parser": "^8.51.0",
-    "husky": "^9.1.7",
-    "eslint": "^8.46.0",
-    "eslint-plugin-import": "^2.30.0",
+    "eslint": "^9.39.2",
     "eslint-config-prettier": "^9.1.0",
-    "eslint-config-standard": "^17.1.0",
-    "eslint-plugin-jest": "^27.2.3",
+    "eslint-plugin-import": "^2.31.0",
+    "eslint-plugin-jest": "^28.0.0",
     "eslint-plugin-jest-playwright": "^0.9.0",
     "eslint-plugin-prettier": "^5.2.1",
-    "eslint-plugin-promise": "^6.1.1",
-    "eslint-plugin-n": "^15.7.0",
-    "eslint-plugin-standard": "^5.0.0",
+    "globals": "^15.0.0",
+    "husky": "^9.1.7",
     "lint-staged": "^13.1.2",
-    "prettier": "^3.7.3"
+    "prettier": "^3.7.3",
+    "typescript-eslint": "^8.48.0"
   },
   "lint-staged": {
     "*.{js,ts}": [