test eslint ecmaVersion impact

.eslintrc.js

// eslint-disable-next-line no-undef
module.exports = {
  // If the line below is commented out, the eslint default parser is used,
  // and the parserOptions.ecmaVersion becomes meaningful; it must be incremented
  // to a value greater than 2024 to parse the entire test.js file.
  // When the babel eslint-parser is used, the ecmaVersion option is ignored.
  parser: "@babel/eslint-parser",
  parserOptions: {
    ecmaVersion: 2017,
    requireConfigFile: false,
    babelOptions: {
      plugins: [["@babel/plugin-proposal-decorators", { version: "2023-11" }]],
    },
  },
  extends: ["eslint:recommended"],
};

package.json

{
  "name": "test-eslint",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/eslint-parser": "^7.27.0",
    "@babel/plugin-proposal-decorators": "^7.25.9",
    "eslint": "^8.0.0"
  }
}

test.js

let tests = {};

tests.objspread = { ...{} }; // es2018
tests.bign_syntaxt = 10n; // es2020
let undef;
tests.nullish = undef ?? "foo"; // es2020
tests.logical_assign ??= true; // es2021
tests.regexp_indices = /foo/dg; // es2022
tests.regexp_unicode = /foo/v; // es2024

// class annotation below requires:
//   parser: @babel/eslint-parser
//   with babelOptions:
//     plugins: [["@babel/plugin-proposal-decorators", { version: "2023-11" }]],

// @annotation
// // eslint-disable-next-line no-unused-vars
// class MyClass {}

// function annotation(target) {
//   target.annotated = true;
// }