From ee6e0acc2e5986b762d1b614bdab55faef6227b5 Mon Sep 17 00:00:00 2001
From: Khiet Tam Nguyen <nktnet999@gmail.com>
Date: Fri, 20 Oct 2023 17:50:11 +1100
Subject: [PATCH] Implementation and documentation updated - now allows for
 pure-esm to be imported into cjs

---
 README.md     |  2 ++
 src/files.ts  | 17 -----------------
 src/import.ts | 35 +++++++++++++++++++++++++----------
 3 files changed, 27 insertions(+), 27 deletions(-)
 delete mode 100644 src/files.ts

diff --git a/README.md b/README.md
index 472f4b0..8be7376 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,8 @@ Synchronously import dynamic ECMAScript Modules similar to CommonJS [require](ht
 
 Basic wrapper around [esm](https://github.com/standard-things/esm) for compatibility with both ES6 and CJS projects in NodeJS
 
+Capable of importing pure-esm libraries such as node-fetch@3 in CJS projects
+
 [![Try with Replit](https://replit.com/badge?caption=Try%20with%20Replit)](https://replit.com/@nktnet1/import-sync-example#index.js)
 
 </div>
diff --git a/src/files.ts b/src/files.ts
deleted file mode 100644
index 00493fb..0000000
--- a/src/files.ts
+++ /dev/null
@@ -1,17 +0,0 @@
-/**
- * Get the file path of the caller function.
- *
- * Implementation inspired by:
- * - https://www.npmjs.com/package/callsite?activeTab=code
- *
- * @returns {string} absolute path or an empty string if no caller
- */
-export const getCallerFilePath = (): string => {
-  const orig = Error.prepareStackTrace;
-  Error.prepareStackTrace = (_, stack) => stack;
-  const err = new Error();
-  Error.captureStackTrace(err, getCallerFilePath);
-  const stack = err.stack as any;
-  Error.prepareStackTrace = orig;
-  return stack[1].getFileName();
-};
diff --git a/src/import.ts b/src/import.ts
index 14acf8c..5d8e3d3 100644
--- a/src/import.ts
+++ b/src/import.ts
@@ -1,21 +1,36 @@
+import esm from 'esm';
 import path from 'path';
-import { getCallerFilePath } from './files';
+import fs from 'fs';
 import { ESMOptions, Options } from './types';
 
 /**
  * Creates an esm-compatible require function that can import ES Modules
  *
- * Removes the error for "[ERR_REQUIRE_ESM]: require() of ES Module", as per
- * - https://github.com/standard-things/esm/issues/855#issuecomment-657982788
- *
  * @returns an ESM-compatible require function
  */
+/* istanbul ignore next */
 const createEs6Require = (esmOptions: ESMOptions) => {
-  /* istanbul ignore next */
+  /**
+   * Removes the error for "[ERR_REQUIRE_ESM]: require() of ES Module", as per
+   * - https://github.com/standard-things/esm/issues/855#issuecomment-657982788
+   */
   require('module').Module._extensions['.js'] = (m: any, filename: string) => {
-    m._compile(require('fs').readFileSync(filename, 'utf-8'), filename);
+    m._compile(fs.readFileSync(filename, 'utf-8'), filename);
+  };
+  const loader = esm(module, esmOptions);
+
+  const newModule = module.constructor.length > 1 ? module.constructor : loader('module');
+  const oldResolveFilename = newModule._resolveFilename;
+  /**
+   * Referencing
+   * - https://github.com/kenotron/esm-jest/commit/624b9524ee698f5cbd16ee2481dc4cd0dec52e42
+   * - https://github.com/standard-things/esm/issues/331#issuecomment-377056717
+   */
+  newModule._resolveFilename = function(request: string, parent: any, isMain: boolean) {
+    const newRequest = request.startsWith('node:') ? request.substring(5) : request;
+    return oldResolveFilename.call(this, newRequest, parent, isMain);
   };
-  return require('esm')(module, esmOptions);
+  return loader;
 };
 
 /**
@@ -26,13 +41,13 @@ const createEs6Require = (esmOptions: ESMOptions) => {
  * @param {Options} [options] - options as defined in types.ts
  * @returns the imported module
  */
-const importSync = (relativePath: string, options: Options = {}) => {
+const importSync = (id: string, options: Options = {}) => {
   const defaultOptions: Required<Options> = {
-    basePath: path.dirname(getCallerFilePath()),
+    basePath: require.main?.path || '',
     esmOptions: {},
   };
   const opts = { ...defaultOptions, ...options };
-  const filePath = path.join(opts.basePath, relativePath);
+  const filePath = path.join(opts.basePath, id);
   const es6Require = createEs6Require(opts.esmOptions);
   try {
     return es6Require(filePath);