fix: use acorn and drop babel-loader by default (#9320)

packages/webpack5/src/configuration/base.ts

@@ -208,19 +208,11 @@ export default function (config: Config, env: IWebpackEnv = _env): Config {
 	});
 
 	// set up js
-	// todo: do we need babel-loader? It's useful to support it
 	config.module
 		.rule('js')
 		.test(/\.js$/)
 		.exclude.add(/node_modules/)
-		.end()
-		.use('babel-loader')
-		.loader('babel-loader')
-		.options({
-			generatorOpts: {
-				compact: false,
-			},
-		});
+		.end();
 
 	config.module
 		.rule('workers')

packages/webpack5/src/index.ts

@@ -1,3 +1,11 @@
+// Make sure the Acorn Parser (used by Webpack) can parse ES-Stage3 code
+// This must be at the top BEFORE webpack is loaded so that we can extend
+// and replace the parser before webpack uses it
+// Based on the issue: https://github.com/webpack/webpack/issues/10216
+const stage3 = require('acorn-stage3');
+const acorn = require('acorn');
+acorn.Parser = acorn.Parser.extend(stage3);
+
 import { highlight } from 'cli-highlight';
 import { merge } from 'webpack-merge';
 import Config from 'webpack-chain';