Improve CJS/ESM interoperability support

.gitignore

@@ -1,6 +1,8 @@
+/.idea/
 /node_modules/
 
 /dist/
+/package/
 /tmp-commonjs-index.ts
 
 /coverage/

bin/build-helmet.js

@@ -2,36 +2,51 @@
 import * as path from "path";
 import { fileURLToPath } from "url";
 import rollupTypescript from "@rollup/plugin-typescript";
-import { writeRollup, withCommonJsFile } from "./helpers.js";
+import {
+  writeRollup,
+  withCommonJsFile,
+  withEsmFile,
+  renameFile,
+  finalizeCommonJs,
+} from "./helpers.js";
 
 const thisPath = fileURLToPath(import.meta.url);
 const rootPath = path.join(path.dirname(thisPath), "..");
 const esmSourcePath = path.join(rootPath, "index.ts");
-const esmDistPath = path.join(rootPath, "dist", "index.js");
-const commonJsDistPath = path.join(rootPath, "dist", "index.cjs");
+const esmDistDir = path.join(rootPath, "dist", "esm");
+const esmDistPath = path.join(esmDistDir, "index.js");
+const commonJsDistDir = path.join(rootPath, "dist", "cjs");
+const commonJsDistPath = path.join(commonJsDistDir, "index.js");
 
 const compileEsm = () =>
-  writeRollup(
-    {
-      input: esmSourcePath,
-      plugins: [rollupTypescript({ tsconfig: "./tsconfig-esm.json" })],
-    },
-    { file: esmDistPath }
+  withEsmFile(esmSourcePath, (esmTempPath) =>
+    writeRollup(
+      {
+        input: esmTempPath,
+        plugins: [rollupTypescript({ tsconfig: "./tsconfig-esm.json" })],
+      },
+      { file: esmDistPath }
+    ).then(() =>
+      renameFile(
+        path.join(esmDistDir, "tmp-esm-index.d.ts"),
+        path.join(esmDistDir, "index.d.ts")
+      )
+    )
   );
 
 const compileCommonjs = () =>
-  withCommonJsFile(esmSourcePath, (commonJsSourcePath) =>
+  withCommonJsFile(esmSourcePath, (commonJsTempPath) =>
     writeRollup(
       {
-        input: commonJsSourcePath,
+        input: commonJsTempPath,
         plugins: [rollupTypescript({ tsconfig: "./tsconfig-commonjs.json" })],
       },
       {
-        exports: "default",
+        exports: "named",
         file: commonJsDistPath,
         format: "cjs",
       }
-    )
+    ).then(async () => await finalizeCommonJs(commonJsDistDir, esmDistDir))
   );
 
 async function main() {

bin/helpers.js

@@ -8,23 +8,74 @@ export async function writeRollup(inputOptions, outputOptions) {
   await bundle.close();
 }
 
+export async function withEsmFile(esmSourcePath, fn) {
+  const esmTempPath = path.join(
+    path.dirname(esmSourcePath),
+    "tmp-esm-index.ts"
+  );
+
+  const lines = (await fs.readFile(esmSourcePath, "utf8")).split(/\r?\n/);
+  const startLine = lines.findIndex((line) =>
+    line.includes("!helmet-start-of-commonjs-exports")
+  );
+  const endLine = lines.findIndex((line) =>
+    line.includes("!helmet-end-of-commonjs-exports")
+  );
+  const lineCount = endLine - startLine + 1;
+  lines.splice(startLine, lineCount);
+
+  try {
+    await fs.writeFile(esmTempPath, lines.join("\n"));
+
+    await fn(esmTempPath);
+  } finally {
+    await fs.unlink(esmTempPath);
+  }
+}
+
 export async function withCommonJsFile(esmSourcePath, fn) {
-  const commonJsSourcePath = path.join(
+  const commonJsTempPath = path.join(
     path.dirname(esmSourcePath),
     "tmp-commonjs-index.ts"
   );
 
   const lines = (await fs.readFile(esmSourcePath, "utf8")).split(/\r?\n/);
-  const resultLines = lines.slice(
-    0,
-    lines.findIndex((line) => line.includes("!helmet-end-of-commonjs"))
+  const startLine = lines.findIndex((line) =>
+    line.includes("!helmet-start-of-commonjs-exports")
+  );
+  const endLine = lines.findIndex((line) =>
+    line.includes("!helmet-end-of-commonjs-exports")
   );
+  lines.splice(startLine, 1);
+  const resultLines = lines.slice(0, endLine);
 
   try {
-    await fs.writeFile(commonJsSourcePath, resultLines.join("\n"));
+    await fs.writeFile(commonJsTempPath, resultLines.join("\n"));
 
-    await fn(commonJsSourcePath);
+    await fn(commonJsTempPath);
   } finally {
-    await fs.unlink(commonJsSourcePath);
+    await fs.unlink(commonJsTempPath);
   }
 }
+
+export function renameFile(oldPath, newPath) {
+  fs.rename(oldPath, newPath),
+    (error) => {
+      if (error) console.error(error);
+    };
+}
+
+export async function finalizeCommonJs(commonJsDistDir, esmDistDir) {
+  const cjsPackageJson = JSON.stringify({
+    type: "commonjs",
+  });
+
+  await fs.writeFile(
+    path.join(commonJsDistDir, "package.json"),
+    cjsPackageJson
+  );
+  await fs.copyFile(
+    path.join(esmDistDir, "index.d.ts"),
+    path.join(commonJsDistDir, "index.d.ts")
+  );
+}

index.ts

@@ -273,7 +273,10 @@ const helmet: Helmet = Object.assign(
 
 export default helmet;
 
-// !helmet-end-of-commonjs
+// !helmet-start-of-commonjs-exports
+exports = helmet;
+module.exports = helmet;
+// !helmet-end-of-commonjs-exports
 
 export {
   contentSecurityPolicy,

package.json

@@ -54,13 +54,15 @@
   },
   "license": "MIT",
   "type": "module",
-  "types": "./dist/index.d.ts",
-  "main": "./dist/index.cjs",
+  "main": "./dist/cjs/index.js",
+  "module": "./dist/esm/index.js",
   "exports": {
     ".": {
-      "import": "./dist/index.js",
-      "require": "./dist/index.cjs",
-      "types": "./dist/index.d.ts"
+      "import": "./dist/esm/index.js",
+      "require": "./dist/cjs/index.js"
     }
-  }
+  },
+  "files": [
+    "dist"
+  ]
 }

tsconfig-esm.json

@@ -1,9 +1,8 @@
 {
   "extends": "./tsconfig",
-  "exclude": ["dist"],
   "compilerOptions": {
-    "outDir": "dist",
     "declaration": true,
     "declarationDir": "."
-  }
+  },
+  "include": ["tmp-esm-index.ts"]
 }

tsconfig.json

@@ -9,6 +9,8 @@
     "noUnusedParameters": true,
     "noUncheckedIndexedAccess": true,
     "strict": true,
-    "target": "es6"
-  }
+    "target": "es6",
+    "outDir": "."
+  },
+  "exclude": ["node_modules", "bin", "dist"]
 }