Fix default export for some bundlers

See [#415](#415).

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Fixed
+
+- Fix issue with TypeScript default exports. See [#417](https://github.com/helmetjs/helmet/pull/417)
+
 ## 6.1.2 - 2023-04-09
 
 ### Fixed

build/build-package.ts

@@ -103,7 +103,11 @@ async function buildCjs({
     exports: "named",
     format: "cjs",
     generatedCode: "es2015",
-    outro: "module.exports = exports.default;",
+    outro: [
+      "module.exports = helmet;",
+      // Some bundlers import with CommonJS but then pull `default` off.
+      "module.exports.default = helmet;",
+    ].join("\n"),
   });
 
   await bundle.close();

test/project-setups/javascript-commonjs-default-member/package.json

@@ -0,0 +1,7 @@
+{
+  "private": true,
+  "type": "commonjs",
+  "scripts": {
+    "helmet:test": "node test.js"
+  }
+}

test/project-setups/javascript-commonjs-default-member/test.js

@@ -0,0 +1,31 @@
+const connect = require("connect");
+const supertest = require("supertest");
+const { default: helmet, frameguard } = require("helmet");
+
+const handler = (_, res) => res.end("Hello world");
+
+async function testTopLevel() {
+  const app = connect().use(helmet()).use(handler);
+  await supertest(app)
+    .get("/")
+    .expect(200, "Hello world")
+    .expect("x-download-options", "noopen");
+}
+
+async function testMiddleware() {
+  const app = connect().use(frameguard()).use(handler);
+  await supertest(app)
+    .get("/")
+    .expect(200, "Hello world")
+    .expect("x-frame-options", "SAMEORIGIN");
+}
+
+async function main() {
+  await testTopLevel();
+  await testMiddleware();
+}
+
+main().catch((err) => {
+  console.error(err);
+  process.exit(1);
+});