Expose CJS proxy in @babel/core

packages/babel-core/package.json

@@ -4,6 +4,10 @@
   "description": "Babel compiler core.",
   "type": "module",
   "main": "./lib/index.js",
+  "exports": {
+    "require": "./proxy.cjs",
+    "default": "./lib/index.js"
+  },
   "author": "The Babel Team (https://babel.dev/team)",
   "license": "MIT",
   "publishConfig": {

packages/babel-core/proxy.cjs

@@ -0,0 +1,25 @@
+"use strict";
+
+const babelP = import("./lib/index.js");
+
+proxy("createConfigItem");
+proxy("loadPartialConfig");
+proxy("loadOptions");
+proxy("transform");
+proxy("transformFile");
+proxy("transformFromAst");
+proxy("parse");
+
+function proxy(name) {
+  exports[`${name}Sync`] = () => {
+    throw new Error(
+      "Only async methods are supported when using `require()` to load `@babel/core`."
+    );
+  };
+  exports[`${name}Async`] = (...args) =>
+    babelP.then(babel => babel[`${name}Async`](...args));
+  exports[name] = (...args) => {
+    const cb = args.pop();
+    babelP.then(babel => babel[name](...args, cb), cb);
+  };
+}