Update eslint to v9

eslint.config.mjs

@@ -1,27 +1,13 @@
-// Automatically generated by running npx @eslint/migrate-config .eslintrc.json
-
-import path from "node:path";
-import { fileURLToPath } from "node:url";
-
-import { fixupConfigRules, fixupPluginRules } from "@eslint/compat";
-import { FlatCompat } from "@eslint/eslintrc";
-import js from "@eslint/js";
-import typescriptEslint from "@typescript-eslint/eslint-plugin";
-import tsParser from "@typescript-eslint/parser";
-import filenames from "eslint-plugin-filenames";
+import { fixupPluginRules } from "@eslint/compat";
 import github from "eslint-plugin-github";
-import _import from "eslint-plugin-import";
+import { importX, createNodeResolver } from "eslint-plugin-import-x";
+import { createTypeScriptImportResolver } from "eslint-import-resolver-typescript";
 import noAsyncForeach from "eslint-plugin-no-async-foreach";
 import jsdoc from "eslint-plugin-jsdoc";
+import tseslint from "typescript-eslint";
 import globals from "globals";
 
-const __filename = fileURLToPath(import.meta.url);
-const __dirname = path.dirname(__filename);
-const compat = new FlatCompat({
-  baseDirectory: __dirname,
-  recommendedConfig: js.configs.recommended,
-  allConfig: js.configs.all,
-});
+const githubFlatConfigs = github.getFlatConfigs();
 
 export default [
   {
@@ -36,29 +22,29 @@ export default [
       ".github/**/*",
     ],
   },
-  ...fixupConfigRules(
-    compat.extends(
-      "eslint:recommended",
-      "plugin:@typescript-eslint/recommended",
-      "plugin:@typescript-eslint/recommended-requiring-type-checking",
-      "plugin:github/recommended",
-      "plugin:github/typescript",
-      "plugin:import/typescript",
-    ),
-  ),
+  // eslint-plugin-github recommended config (includes eslint:recommended,
+  // eslint-plugin-import, eslint-comments, i18n-text, and github rules).
+  githubFlatConfigs.recommended,
+  // eslint-plugin-github typescript config (includes
+  // @typescript-eslint/recommended and escompat).
+  ...githubFlatConfigs.typescript,
+  // Type-checked rules from typescript-eslint (the github plugin only
+  // includes the base recommended rules, not the type-checked ones).
+  ...tseslint.configs.recommendedTypeCheckedOnly,
+  // import-x TypeScript settings (parsers, extensions, external-module-folders).
+  // This is needed for import-x rules to properly parse TypeScript files.
+  {
+    settings: importX.flatConfigs.typescript.settings,
+  },
   {
     plugins: {
-      "@typescript-eslint": fixupPluginRules(typescriptEslint),
-      filenames: fixupPluginRules(filenames),
-      github: fixupPluginRules(github),
-      import: fixupPluginRules(_import),
-      "no-async-foreach": noAsyncForeach,
+      "import-x": importX,
+      "no-async-foreach": fixupPluginRules(noAsyncForeach),
       "jsdoc": jsdoc,
     },
 
     languageOptions: {
-      parser: tsParser,
-      ecmaVersion: 5,
+      ecmaVersion: "latest",
       sourceType: "module",
 
       globals: {
@@ -79,10 +65,16 @@ export default [
         typescript: {},
       },
       "import/ignore": ["sinon", "uuid", "@octokit/plugin-retry", "del", "get-folder-size"],
+      "import-x/resolver-next": [
+        createTypeScriptImportResolver(),
+        createNodeResolver({
+          extensions: [".ts", ".js", ".json"],
+        }),
+      ],
     },
 
     rules: {
-      "filenames/match-regex": ["error", "^[a-z0-9-]+(\\.test)?$"],
+      "github/filenames-match-regex": ["error", "^[a-z0-9-]+(\\.test)?$"],
       "i18n-text/no-en": "off",
 
       "import/extensions": [
@@ -94,7 +86,10 @@ export default [
 
       "import/no-amd": "error",
       "import/no-commonjs": "error",
-      "import/no-cycle": "error",
+      // import/no-cycle does not seem to work with ESLint 9.
+      // Use import-x/no-cycle from eslint-plugin-import-x instead.
+      "import/no-cycle": "off",
+      "import-x/no-cycle": "error",
       "import/no-dynamic-require": "error",
 
       "import/no-extraneous-dependencies": [