From 114e4c8786755a74c1135fd58702f07d9a349c18 Mon Sep 17 00:00:00 2001
From: Antoine du Hamel <duhamelantoine1995@gmail.com>
Date: Wed, 10 Mar 2021 23:20:38 +0100
Subject: [PATCH] module: improve error message for invalid data URL

Fixes: https://github.com/nodejs/node/issues/37647
---
 lib/internal/modules/esm/loader.js           |  8 ++++++++
 test/es-module/test-esm-invalid-data-urls.js | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 test/es-module/test-esm-invalid-data-urls.js

diff --git a/lib/internal/modules/esm/loader.js b/lib/internal/modules/esm/loader.js
index 232177698c73f6..b52db6cdc4db1f 100644
--- a/lib/internal/modules/esm/loader.js
+++ b/lib/internal/modules/esm/loader.js
@@ -6,6 +6,7 @@ require('internal/modules/cjs/loader');
 const {
   FunctionPrototypeBind,
   ObjectSetPrototypeOf,
+  RegExpPrototypeExec,
   SafeWeakMap,
   StringPrototypeStartsWith,
 } = primordials;
@@ -107,6 +108,13 @@ class Loader {
     }
 
     const { format } = getFormatResponse;
+    if(format === null) {
+      const dataUrl = RegExpPrototypeExec(
+        /^data:([^/]+\/[^;,]+)(?:[^,]*?)(;base64)?,/,
+        url,
+      );
+      throw new ERR_UNKNOWN_MODULE_FORMAT(dataUrl ? dataUrl[1] : 'null');
+    }
     if (typeof format !== 'string') {
       throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
         'string', 'loader getFormat', 'format', format);
diff --git a/test/es-module/test-esm-invalid-data-urls.js b/test/es-module/test-esm-invalid-data-urls.js
new file mode 100644
index 00000000000000..caf8547422be3d
--- /dev/null
+++ b/test/es-module/test-esm-invalid-data-urls.js
@@ -0,0 +1,18 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+
+(async () => {
+  await assert.rejects(import(`data:text/plain,export default0`), {
+    code: 'ERR_UNKNOWN_MODULE_FORMAT',
+    message: 'Unknown module format: text/plain',
+  });
+  await assert.rejects(import(`data:text/plain;base64,`), {
+    code: 'ERR_UNKNOWN_MODULE_FORMAT',
+    message: 'Unknown module format: text/plain',
+  });
+  await assert.rejects(import('data:application/json,[]'), {
+    code: 'ERR_UNKNOWN_MODULE_FORMAT',
+    message: 'Unknown module format: application/json',
+  });
+})().then(common.mustCall());