From 5a269369f39e8c0f4c2f8119df2ef7be73b4bf51 Mon Sep 17 00:00:00 2001
From: Antoine du Hamel <duhamelantoine1995@gmail.com>
Date: Sun, 21 Mar 2021 15:41:24 +0100
Subject: [PATCH] module: clarify CJS global-like variables not defined error
 message

Fixes: https://github.com/nodejs/node/issues/33741
---
 lib/internal/modules/esm/module_job.js        | 41 ++++++++++++++++++-
 ...esm-undefined-cjs-global-like-variables.js | 28 +++++++++++++
 2 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 test/es-module/test-esm-undefined-cjs-global-like-variables.js

diff --git a/lib/internal/modules/esm/module_job.js b/lib/internal/modules/esm/module_job.js
index ebae1940502b4b..f5b1f2495b32a5 100644
--- a/lib/internal/modules/esm/module_job.js
+++ b/lib/internal/modules/esm/module_job.js
@@ -4,6 +4,7 @@ const {
   ArrayPrototypeJoin,
   ArrayPrototypeMap,
   ArrayPrototypePush,
+  ArrayPrototypeSome,
   FunctionPrototype,
   ObjectSetPrototypeOf,
   PromiseAll,
@@ -12,10 +13,12 @@ const {
   ReflectApply,
   SafeArrayIterator,
   SafeSet,
+  StringPrototypeEndsWith,
   StringPrototypeIncludes,
   StringPrototypeMatch,
   StringPrototypeReplace,
   StringPrototypeSplit,
+  StringPrototypeStartsWith,
 } = primordials;
 
 const { ModuleWrap } = internalBinding('module_wrap');
@@ -28,6 +31,19 @@ const noop = FunctionPrototype;
 
 let hasPausedEntry = false;
 
+const CJSGlobalLike = [
+  'require',
+  'module',
+  'exports',
+  '__filename',
+  '__dirname',
+];
+const isCommonJSGlobalLikeNotDefinedError = (errorMessage) =>
+  ArrayPrototypeSome(
+    CJSGlobalLike,
+    (globalLike) => StringPrototypeStartsWith(errorMessage, globalLike)
+  );
+
 /* A ModuleJob tracks the loading of a single Module, and the ModuleJobs of
  * its dependencies, over time. */
 class ModuleJob {
@@ -151,7 +167,30 @@ class ModuleJob {
     await this.instantiate();
     const timeout = -1;
     const breakOnSigint = false;
-    await this.module.evaluate(timeout, breakOnSigint);
+    try {
+      await this.module.evaluate(timeout, breakOnSigint);
+    } catch (e) {
+      if (e.name === 'ReferenceError' &&
+          StringPrototypeEndsWith(e.message, ' is not defined') &&
+          isCommonJSGlobalLikeNotDefinedError(e.message)) {
+        e.message += ' in ES module scope';
+
+        if (StringPrototypeStartsWith(e.message, 'require')) {
+          e.message += '. You can use `await import` instead';
+        }
+
+        if (StringPrototypeEndsWith(this.module.url, '.js') &&
+            StringPrototypeStartsWith(this.module.url, 'file://')) {
+          e.message +=
+            '. It seems you are trying to load a file using `.js` extension ' +
+            'inside a folder containing a `package.json` that includes ' +
+            '`"type": "module"`; you need to use the `.cjs` extension to ' +
+            'load the file as a CommonJS module, or add a `package.json` ' +
+            'file with ``"type": "commonjs"`.';
+        }
+      }
+      throw e;
+    }
     return { module: this.module };
   }
 }
diff --git a/test/es-module/test-esm-undefined-cjs-global-like-variables.js b/test/es-module/test-esm-undefined-cjs-global-like-variables.js
new file mode 100644
index 00000000000000..8a022f8b0df0ba
--- /dev/null
+++ b/test/es-module/test-esm-undefined-cjs-global-like-variables.js
@@ -0,0 +1,28 @@
+'use strict';
+const common = require('../common');
+const fixtures = require('../common/fixtures');
+const assert = require('assert');
+
+assert.rejects(
+  import('data:text/javascript,require;'),
+  // eslint-disable-next-line node-core/no-unescaped-regexp-dot
+  /use .await import. instead/
+).then(common.mustCall());
+
+assert.rejects(
+  import('data:text/javascript,exports={};'),
+  // eslint-disable-next-line node-core/no-unescaped-regexp-dot
+  /^(?!use .await import. instead).*$/
+).then(common.mustCall());
+
+assert.rejects(
+  import('data:text/javascript,require;//.js'),
+  // eslint-disable-next-line node-core/no-unescaped-regexp-dot
+  /^(?!It seems you are trying to load a file using `.js` extension).*$/
+).then(common.mustCall());
+
+assert.rejects(
+  import(fixtures.path('/es-modules/package-type-module/cjs.js')),
+  // eslint-disable-next-line node-core/no-unescaped-regexp-dot
+  /use the .\.cjs. extension to load the file as a CommonJS module/
+).then(common.mustCall());