feat(babel)!: support Babel 8

packages/babel/README.md

@@ -26,7 +26,15 @@ Using Rollup with `@rollup/plugin-babel` makes the process far easier.
 
 ## Requirements
 
-This plugin requires an [LTS](https://github.com/nodejs/Release) Node version (v14.0.0+) and Rollup v1.20.0+.
+This plugin requires Node.js `^22.18.0 || >=24.11.0` (the range supported by Babel 8), Rollup v4.0.0+ and `@babel/core` v8.0.0+. If you are on Babel 7, use `@rollup/plugin-babel` v7.
+
+This package is published as ES modules only. `require('@rollup/plugin-babel')` keeps working on the supported Node versions via [`require(esm)`](https://nodejs.org/api/modules.html#loading-ecmascript-modules-using-require).
+
+## Migration to v8
+
+- Babel 7 is no longer supported, see the [Babel 8 migration guide](https://babeljs.io/docs/v8-migration) for upgrading your Babel configuration.
+- The `runtimeHelpers` and `externalHelpers` plugin options (deprecated since v5 in favour of `babelHelpers`) have been removed.
+- The `@types/babel__core` optional peer dependency is gone; Babel 8 ships its own TypeScript types.
 
 ## Install
 
@@ -110,7 +118,7 @@ const filter = createFilter(include, exclude, {});
 ### `extensions`
 
 Type: `Array[...String]`<br>
-Default: `['.js', '.jsx', '.es6', '.es', '.mjs']`
+Default: `['.js', '.jsx', '.es6', '.es', '.mjs', '.cjs']`
 
 An array of file extensions that Babel should transpile. If you want to transpile TypeScript files with this plugin it's essential to include `.ts` and `.tsx` in this option.
 
@@ -291,15 +299,15 @@ By default, helpers e.g. when transpiling classes will be inserted at the top of
 
 Alternatively, you can use imported runtime helpers by adding the `@babel/transform-runtime` plugin. This will make `@babel/runtime` an external dependency of your project, see [@babel/plugin-transform-runtime](https://babeljs.io/docs/en/babel-plugin-transform-runtime) for details.
 
-Note that this will only work for `es` and `cjs` formats, and you need to make sure to set the `useESModules` option of `@babel/plugin-transform-runtime` to `true` if you create ES output:
+Note that this will only work for `es` and `cjs` formats. Helpers are always imported as `@babel/runtime/helpers/<name>`; whether the ESM or CommonJS flavour is used is resolved from `@babel/runtime`'s `package.json#exports`:
 
 ```js
 rollup.rollup({...})
 .then(bundle => bundle.generate({
   format: 'es',
   plugins: [getBabelOutputPlugin({
     presets: ['@babel/preset-env'],
-    plugins: [['@babel/plugin-transform-runtime', { useESModules: true }]]
+    plugins: ['@babel/plugin-transform-runtime']
   })]
 }))
 ```
@@ -309,7 +317,7 @@ rollup.rollup({...})
 export default class Foo {}
 
 // output
-import _classCallCheck from '@babel/runtime/helpers/esm/classCallCheck';
+import _classCallCheck from '@babel/runtime/helpers/classCallCheck';
 
 var Foo = function Foo() {
   _classCallCheck(this, Foo);
@@ -318,35 +326,6 @@ var Foo = function Foo() {
 export default Foo;
 ```
 
-And for CommonJS:
-
-```js
-rollup.rollup({...})
-.then(bundle => bundle.generate({
-  format: 'cjs',
-  plugins: [getBabelOutputPlugin({
-    presets: ['@babel/preset-env'],
-    plugins: [['@babel/plugin-transform-runtime', { useESModules: false }]]
-  })]
-}))
-```
-
-```js
-// input
-export default class Foo {}
-
-// output
-('use strict');
-
-var _classCallCheck = require('@babel/runtime/helpers/classCallCheck');
-
-var Foo = function Foo() {
-  _classCallCheck(this, Foo);
-};
-
-module.exports = Foo;
-```
-
 Another option is to use `@babel/plugin-external-helpers`, which will reference the global `babelHelpers` object. It is your responsibility to make sure this global variable exists.
 
 ## Custom plugin builder

packages/babel/package.json

@@ -13,33 +13,25 @@
   "author": "Rich Harris",
   "homepage": "https://github.com/rollup/plugins/tree/master/packages/babel#readme",
   "bugs": "https://github.com/rollup/plugins/issues",
-  "main": "./dist/cjs/index.js",
-  "module": "./dist/es/index.js",
+  "type": "module",
   "exports": {
     "types": "./types/index.d.ts",
-    "import": "./dist/es/index.js",
-    "default": "./dist/cjs/index.js"
+    "default": "./src/index.js"
   },
   "engines": {
-    "node": ">=14.0.0"
+    "node": "^22.18.0 || >=24.11.0"
   },
   "scripts": {
-    "build": "rollup -c",
     "ci:coverage": "nyc pnpm test && nyc report --reporter=text-lcov > coverage.lcov",
-    "ci:lint": "pnpm build && pnpm lint",
+    "ci:lint": "pnpm lint",
     "ci:lint:commits": "commitlint --from=${CIRCLE_BRANCH} --to=${CIRCLE_SHA1}",
     "ci:test": "pnpm test -- --reporter=verbose",
-    "prebuild": "del-cli dist",
-    "prepare": "if [ ! -d 'dist' ]; then pnpm build; fi",
-    "prerelease": "pnpm build",
-    "pretest": "pnpm build",
     "release": "pnpm --workspace-root package:release $(pwd)",
-    "test": "vitest --config ../../.config/vitest.config.mts run",
-    "test:ts": "tsc types/index.d.ts test/types.ts --noEmit"
+    "test": "node ./scripts/run-tests-if-supported.mjs",
+    "test:ts": "tsc types/index.d.ts test/types.ts --noEmit --esModuleInterop"
   },
   "files": [
-    "dist",
-    "!dist/**/*.map",
+    "src",
     "types",
     "README.md",
     "LICENSE"
@@ -53,34 +45,28 @@
     "es6"
   ],
   "peerDependencies": {
-    "@babel/core": "^7.0.0",
-    "@types/babel__core": "^7.1.9",
-    "rollup": "^2.0.0||^3.0.0||^4.0.0"
+    "@babel/core": "^8.0.0",
+    "rollup": ">=4.0.0"
   },
   "peerDependenciesMeta": {
     "rollup": {
       "optional": true
-    },
-    "@types/babel__core": {
-      "optional": true
     }
   },
   "dependencies": {
-    "@babel/helper-module-imports": "^7.18.6",
+    "@babel/helper-module-imports": "^8.0.0",
     "@rollup/pluginutils": "^5.0.1",
     "workerpool": "^9.0.0"
   },
   "devDependencies": {
-    "@babel/core": "^7.19.1",
-    "@babel/plugin-external-helpers": "^7.18.6",
-    "@babel/plugin-proposal-decorators": "^7.19.1",
-    "@babel/plugin-syntax-dynamic-import": "^7.8.3",
-    "@babel/plugin-transform-runtime": "^7.19.1",
-    "@babel/preset-env": "^7.19.1",
+    "@babel/core": "^8.0.1",
+    "@babel/plugin-external-helpers": "^8.0.1",
+    "@babel/plugin-proposal-decorators": "^8.0.2",
+    "@babel/plugin-transform-runtime": "^8.0.1",
+    "@babel/preset-env": "^8.0.2",
     "@rollup/plugin-json": "^5.0.0",
     "@rollup/plugin-node-resolve": "^15.0.0",
-    "@types/babel__core": "^7.1.9",
-    "rollup": "^4.0.0-24",
+    "rollup": "^4.0.0",
     "source-map": "^0.7.4"
   },
   "types": "./types/index.d.ts",

packages/babel/scripts/run-tests-if-supported.mjs

@@ -0,0 +1,22 @@
+#!/usr/bin/env node
+// Babel 8 requires Node ^22.18.0 || >=24.11.0, but the repo-wide CI matrix also
+// runs older Node versions. Skip this package's tests there instead of failing.
+import { spawn } from 'node:child_process';
+
+const [major, minor] = process.versions.node.split('.').map(Number);
+const supported = (major === 22 && minor >= 18) || (major === 24 && minor >= 11) || major >= 25;
+
+if (!supported) {
+  // eslint-disable-next-line no-console
+  console.log(
+    `skipping tests: Babel 8 requires Node ^22.18.0 || >=24.11.0 (running ${process.versions.node})`
+  );
+  process.exit(0);
+}
+
+const child = spawn(
+  'vitest',
+  ['--config', '../../.config/vitest.config.mts', 'run', ...process.argv.slice(2)],
+  { stdio: 'inherit', shell: process.platform === 'win32' }
+);
+child.on('exit', (code) => process.exit(code ?? 1));

packages/babel/src/index.js

@@ -31,26 +31,8 @@ const unpackOptions = ({
   };
 };
 
-const warnAboutDeprecatedHelpersOption = ({ deprecatedOption, suggestion }) => {
-  // eslint-disable-next-line no-console
-  console.warn(
-    `\`${deprecatedOption}\` has been removed in favor a \`babelHelpers\` option. Try changing your configuration to \`${suggestion}\`. ` +
-      `Refer to the documentation to learn more: https://github.com/rollup/plugins/tree/master/packages/babel#babelhelpers`
-  );
-};
-
 const unpackInputPluginOptions = ({ skipPreflightCheck = false, ...rest }) => {
-  if ('runtimeHelpers' in rest) {
-    warnAboutDeprecatedHelpersOption({
-      deprecatedOption: 'runtimeHelpers',
-      suggestion: `babelHelpers: 'runtime'`
-    });
-  } else if ('externalHelpers' in rest) {
-    warnAboutDeprecatedHelpersOption({
-      deprecatedOption: 'externalHelpers',
-      suggestion: `babelHelpers: 'external'`
-    });
-  } else if (!rest.babelHelpers) {
+  if (!rest.babelHelpers) {
     // eslint-disable-next-line no-console
     console.warn(
       "babelHelpers: 'bundled' option was used by default. It is recommended to configure this option explicitly, read more here: " +
@@ -330,11 +312,8 @@ function createBabelOutputPluginFactory(customCallback = returnObject) {
           excludeChunks,
           exclude,
           extensions,
-          externalHelpers,
-          externalHelpersWhitelist,
           include,
           parallel,
-          runtimeHelpers,
           ...babelOptions
         } = unpackOutputPluginOptions(pluginOptionsWithOverrides, outputOptions);
         /* eslint-enable no-unused-vars */
@@ -392,3 +371,15 @@ export { createBabelInputPluginFactory, createBabelOutputPluginFactory };
 export default getBabelInputPlugin;
 // support `rollup -c —plugin babel`
 export { getBabelInputPlugin as babel };
+
+// make `require('@rollup/plugin-babel')` return the callable default export with
+// the named exports attached, like the removed CJS build did
+const cjsExports = Object.assign(getBabelInputPlugin, {
+  default: getBabelInputPlugin,
+  babel: getBabelInputPlugin,
+  getBabelInputPlugin,
+  getBabelOutputPlugin,
+  createBabelInputPluginFactory,
+  createBabelOutputPluginFactory
+});
+export { cjsExports as 'module.exports' };

packages/babel/src/preflightCheck.js

@@ -34,8 +34,7 @@ function helpersTestTransform() {
 const mismatchError = (actual, expected, filename) =>
   `You have declared using "${expected}" babelHelpers, but transforming ${filename} resulted in "${actual}". Please check your configuration.`;
 
-// Revert to /\/helpers\/(esm\/)?inherits/ when Babel 8 gets released, this was fixed in https://github.com/babel/babel/issues/14185
-const inheritsHelperRe = /[\\/]+helpers[\\/]+(esm[\\/]+)?inherits/;
+const inheritsHelperRe = /\/helpers\/(esm\/)?inherits/;
 
 export default async function preflightCheck(error, babelHelpers, transformOptions) {
   const finalOptions = addBabelPlugin(transformOptions, helpersTestTransform);

packages/babel/src/transformCode.js

@@ -14,8 +14,7 @@ export default async function transformCode({
   skipPreflightCheck,
   babelHelpers
 }) {
-  // loadPartialConfigAsync has become available in @babel/core@7.8.0
-  const config = await (babel.loadPartialConfigAsync || babel.loadPartialConfig)(babelOptions);
+  const config = await babel.loadPartialConfigAsync(babelOptions);
 
   // file is ignored by babel
   if (!config) {

packages/babel/test/as-input-plugin.mjs

@@ -216,7 +216,8 @@ test('generates sourcemap by default', async () => {
     source: 'test/fixtures/class/main.js'.split(nodePath.sep).join('/'),
     line: 3,
     column: 12,
-    name: target
+    // Babel 8 no longer records a name mapping for identifiers whose text is unchanged
+    name: null
   });
 });
 test('works with proposal-decorators (rollup/rollup-plugin-babel#18)', async () => {
@@ -273,7 +274,7 @@ var Foo = /*#__PURE__*/_createClass(function Foo() {
 module.exports = Foo;
 `);
 });
-test('allows transform-runtime to inject esm version of helpers', async () => {
+test('allows transform-runtime to inject helpers in esm output', async () => {
   const warnings = [];
   const code = await generate(
     'runtime-helpers-esm/main.js',
@@ -290,11 +291,11 @@ test('allows transform-runtime to inject esm version of helpers', async () => {
     }
   );
   expect(warnings).toEqual([
-    `"@babel/runtime/helpers/esm/createClass" is imported by "test/fixtures/runtime-helpers-esm/main.js", but could not be resolved – treating it as an external dependency.`,
-    `"@babel/runtime/helpers/esm/classCallCheck" is imported by "test/fixtures/runtime-helpers-esm/main.js", but could not be resolved – treating it as an external dependency.`
+    `"@babel/runtime/helpers/createClass" is imported by "test/fixtures/runtime-helpers-esm/main.js", but could not be resolved – treating it as an external dependency.`,
+    `"@babel/runtime/helpers/classCallCheck" is imported by "test/fixtures/runtime-helpers-esm/main.js", but could not be resolved – treating it as an external dependency.`
   ]);
-  expect(code).toBe(`import _createClass from '@babel/runtime/helpers/esm/createClass';
-import _classCallCheck from '@babel/runtime/helpers/esm/classCallCheck';
+  expect(code).toBe(`import _createClass from '@babel/runtime/helpers/createClass';
+import _classCallCheck from '@babel/runtime/helpers/classCallCheck';
 
 var Foo = /*#__PURE__*/_createClass(function Foo() {
   _classCallCheck(this, Foo);
@@ -573,7 +574,7 @@ test('can be used as an input plugin while transforming the output', async () =>
     input: `${FIXTURES}basic/main.js`,
     plugins: [
       getBabelOutputPlugin({
-        presets: ['@babel/env']
+        presets: [['@babel/env', { targets: { ie: '11' } }]]
       })
     ]
   });
@@ -587,7 +588,7 @@ test('works as a CJS plugin', async () => {
     input: `${FIXTURES}basic/main.js`,
     plugins: [
       babelPluginCjs({
-        presets: ['@babel/env']
+        presets: [['@babel/env', { targets: { ie: '11' } }]]
       })
     ]
   });
@@ -603,7 +604,7 @@ test('works in parallel as a CJS plugin', async () => {
     plugins: [
       babelPluginCjs({
         babelHelpers: 'bundled',
-        presets: ['@babel/env'],
+        presets: [['@babel/env', { targets: { ie: '11' } }]],
         parallel: true
       })
     ]