Migrate to ESLint v9.

Author: jaydenseric

.eslintrc.json

@@ -19,6 +19,7 @@
 - Updated the `package.json` field `repository` to conform to new npm requirements.
 - Updated GitHub Actions CI config:
   - Updated the tested Node.js versions to v18, v20.
+- Migrated to the ESLint v9 CLI and “flat” config.
 - Removed the Node.js CLI option `--unhandled-rejections=throw` in the package script `tests` as it’s now the default for all supported Node.js versions.
 - Omit unused catch bindings in the function `processRequest`.
 

changelog.md

@@ -0,0 +1,66 @@
+// @ts-check
+
+import eslintJs from "@eslint/js";
+import eslintPluginSimpleImportSort from "eslint-plugin-simple-import-sort";
+import globals from "globals";
+
+/** @import { Linter } from "eslint" */
+
+/**
+ * Globs for ESM files.
+ * @satisfies {Array<string>}
+ */
+const globsEsm = ["**/**.mjs"];
+
+/**
+ * Globs for CJS files.
+ * @satisfies {Array<string>}
+ */
+const globsCjs = ["**/**.cjs", "**/**.js"];
+
+/**
+ * Globs for all JavaScript files.
+ * @satisfies {Array<string>}
+ */
+const globsJs = [...globsEsm, ...globsCjs];
+
+/**
+ * ESLint configuration.
+ * @satisfies {Array<Linter.FlatConfig>}
+ */
+const eslintConfig = [
+  {
+    files: globsJs,
+    ...eslintJs.configs.recommended,
+  },
+  {
+    files: globsJs,
+    rules: {
+      "arrow-body-style": "error",
+      "object-shorthand": "error",
+      strict: "error",
+    },
+  },
+  {
+    files: globsEsm,
+    languageOptions: {
+      globals: globals.nodeBuiltin,
+    },
+    plugins: {
+      "simple-import-sort": eslintPluginSimpleImportSort,
+    },
+    rules: {
+      "simple-import-sort/imports": "error",
+      "simple-import-sort/exports": "error",
+    },
+  },
+  {
+    files: globsCjs,
+    languageOptions: {
+      sourceType: "commonjs",
+      globals: globals.node,
+    },
+  },
+];
+
+export default eslintConfig;

eslint.config.mjs

@@ -73,20 +73,22 @@
     "object-path": "^0.11.8"
   },
   "devDependencies": {
+    "@eslint/js": "^9.11.1",
     "@types/express": "^5.0.0",
     "@types/koa": "^2.15.0",
     "coverage-node": "^8.0.0",
-    "eslint": "^8.57.1",
+    "eslint": "^9.11.1",
     "eslint-plugin-simple-import-sort": "^12.1.1",
     "express": "^5.0.0",
     "form-data-encoder": "^4.0.2",
+    "globals": "^15.10.0",
     "graphql": "^16.9.0",
     "koa": "^2.15.3",
     "prettier": "^3.3.3",
     "typescript": "^5.6.2"
   },
   "scripts": {
-    "eslint": "eslint .",
+    "eslint": "eslint",
     "prettier": "prettier -c .",
     "types": "tsc -p jsconfig.json",
     "tests": "coverage-node --test-reporter=spec --test *.test.mjs",