perf: replace Babel with esbuild for ESM to CJS transformation and update dependencies

lib/detector.ts

@@ -80,6 +80,7 @@ function reconstructSpecifiers(
 }
 
 function reconstruct(node: babelTypes.Node) {
+  // @ts-expect-error Type mismatch due to @babel/types version in @types/babel__generator
   let v = generate(node, { comments: false }).code.replace(/\n/g, '');
   let v2;
 

lib/esm-transformer.ts

@@ -1,5 +1,7 @@
-import * as babel from '@babel/core';
+import * as babel from '@babel/parser';
 import traverse, { NodePath } from '@babel/traverse';
+import * as t from '@babel/types';
+import * as esbuild from 'esbuild';
 import { log } from './log';
 import { unlikelyJavascript } from './common';
 
@@ -29,8 +31,7 @@ function detectUnsupportedESMFeatures(
   filename: string,
 ): UnsupportedFeature[] | null {
   try {
-    const ast = babel.parseSync(code, {
-      filename,
+    const ast = babel.parse(code, {
       sourceType: 'module',
       plugins: [],
     });
@@ -41,9 +42,10 @@ function detectUnsupportedESMFeatures(
 
     const unsupportedFeatures: UnsupportedFeature[] = [];
 
-    traverse(ast, {
+    // @ts-expect-error Type mismatch due to @babel/types version in @types/babel__traverse
+    traverse(ast as t.File, {
       // Detect import.meta usage
-      MetaProperty(path) {
+      MetaProperty(path: NodePath<t.MetaProperty>) {
         if (
           path.node.meta.name === 'import' &&
           path.node.property.name === 'meta'
@@ -57,7 +59,7 @@ function detectUnsupportedESMFeatures(
       },
 
       // Detect top-level await
-      AwaitExpression(path) {
+      AwaitExpression(path: NodePath<t.AwaitExpression>) {
         // Check if await is at top level (not inside a function)
         let parent: NodePath | null = path.parentPath;
         let isTopLevel = true;
@@ -86,7 +88,7 @@ function detectUnsupportedESMFeatures(
       },
 
       // Detect for-await-of at top level
-      ForOfStatement(path) {
+      ForOfStatement(path: NodePath<t.ForOfStatement>) {
         if (path.node.await) {
           let parent: NodePath | null = path.parentPath;
           let isTopLevel = true;
@@ -129,8 +131,9 @@ function detectUnsupportedESMFeatures(
 }
 
 /**
- * Transform ESM code to CommonJS using Babel
+ * Transform ESM code to CommonJS using esbuild
  * This allows ESM modules to be compiled to bytecode via vm.Script
+ * Uses Babel parser for detecting unsupported ESM features, then esbuild for fast transformation
  *
  * @param code - The ESM source code to transform
  * @param filename - The filename for error reporting
@@ -183,29 +186,17 @@ export function transformESMtoCJS(
   }
 
   try {
-    const result = babel.transformSync(code, {
-      filename,
-      plugins: [
-        [
-          '@babel/plugin-transform-modules-commonjs',
-          {
-            strictMode: true,
-            allowTopLevelThis: true,
-          },
-        ],
-      ],
-      sourceMaps: false,
-      compact: false,
-      // Don't modify other syntax, only transform import/export
-      presets: [],
-      // Prevent Babel from loading user config files
-      babelrc: false,
-      configFile: false,
-      sourceType: 'module',
+    const result = esbuild.transformSync(code, {
+      loader: 'js',
+      format: 'cjs',
+      target: 'node18',
+      sourcemap: false,
+      minify: false,
+      keepNames: true,
     });
 
     if (!result || !result.code) {
-      log.warn(`Babel transform returned no code for ${filename}`);
+      log.warn(`esbuild transform returned no code for ${filename}`);
       return {
         code,
         isTransformed: false,

package.json

@@ -22,12 +22,11 @@
     "singleQuote": true
   },
   "dependencies": {
-    "@babel/core": "^7.23.0",
     "@babel/generator": "^7.23.0",
     "@babel/parser": "^7.23.0",
-    "@babel/plugin-transform-modules-commonjs": "^7.27.1",
     "@babel/traverse": "^7.23.0",
     "@babel/types": "^7.23.0",
+    "esbuild": "^0.24.0",
     "@yao-pkg/pkg-fetch": "3.5.32",
     "into-stream": "^6.0.0",
     "minimist": "^1.2.6",
@@ -44,8 +43,8 @@
   },
   "devDependencies": {
     "@release-it/conventional-changelog": "^7.0.2",
-    "@types/babel__core": "^7.20.5",
     "@types/babel__generator": "^7.6.5",
+    "@types/babel__traverse": "^7.20.3",
     "@types/minimist": "^1.2.2",
     "@types/multistream": "^4.1.0",
     "@types/node": "^16.18.113",
@@ -56,7 +55,6 @@
     "@types/unzipper": "^0.10.10",
     "@typescript-eslint/eslint-plugin": "^6.7.4",
     "@typescript-eslint/parser": "^6.7.4",
-    "esbuild": "^0.24.0",
     "esbuild-register": "^3.6.0",
     "eslint": "^8.50.0",
     "eslint-config-airbnb-base": "^15.0.0",