Add failing test for parallel loading of TLA modules

packages/babel-core/test/async.js

@@ -4,6 +4,7 @@ import * as babel from "../lib/index.js";
 
 import {
   spawnTransformAsync,
+  spawnTransformAsyncParallel,
   spawnTransformSync,
   supportsESM,
 } from "./helpers/esm.js";
@@ -253,6 +254,18 @@ describe("asynchronicity", () => {
           code: `"success"`,
         });
       });
+
+      nodeGte14(
+        "called asynchronously twice in parallel when contain TLA",
+        async () => {
+          process.chdir("config-mjs-tla-native");
+
+          await expect(spawnTransformAsyncParallel()).resolves.toMatchObject([
+            { code: `"success"` },
+            { code: `"success"` },
+          ]);
+        },
+      );
     });
   });
 

packages/babel-core/test/fixtures/async/config-mjs-tla-native/babel.config.js

@@ -0,0 +1,5 @@
+await Promise.resolve(0);
+
+export default {
+  plugins: ["./plugin.js"],
+};

packages/babel-core/test/fixtures/async/config-mjs-tla-native/package.json

@@ -0,0 +1 @@
+{ "type": "module" }

packages/babel-core/test/fixtures/async/config-mjs-tla-native/plugin.js

@@ -0,0 +1,9 @@
+export default function plugin({ types: t }) {
+  return {
+    visitor: {
+      Program(path) {
+        path.pushContainer("body", t.stringLiteral("success"));
+      },
+    },
+  };
+}

packages/babel-core/test/fixtures/babel-compile-async-parallel.mjs

@@ -0,0 +1,12 @@
+#!/usr/bin/env node
+
+// Usage:
+// babel-compile-async-parallel.js [filename]
+import { transformAsync } from "../../lib/index.js";
+
+(async () => {
+  process.stdout.write(JSON.stringify(await Promise.all([
+    transformAsync(""),
+    transformAsync("")
+  ])));
+})();

packages/babel-core/test/helpers/esm.js

@@ -38,6 +38,11 @@ export function spawnTransformAsync() {
   return spawn("compile-async");
 }
 
+export function spawnTransformAsyncParallel() {
+  // import() crashes with jest
+  return spawn("compile-async-parallel");
+}
+
 export function spawnTransformSync() {
   // import() crashes with jest
   return spawn("compile-sync");