module: fix unintended mutation

Refs: #46061 (comment)
PR-URL: #46108
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Jacob Smith <jacob@frende.me>

Author: aduh95

lib/internal/modules/cjs/loader.js

@@ -29,6 +29,7 @@ const {
  ArrayPrototypeJoin,
  ArrayPrototypeMap,
  ArrayPrototypePush,
+ ArrayPrototypePushApply,
  ArrayPrototypeSlice,
  ArrayPrototypeSplice,
  ArrayPrototypeUnshift,
@@ -667,12 +668,11 @@ Module._findPath = function(request, paths, isMain) {
 returnfilename;
 }
 
-if(exts===undefined){
-exts=[''];
-}else{
-ArrayPrototypeUnshift(exts,'');
+constextensions=[''];
+if(exts!==undefined){
+ArrayPrototypePushApply(extensions,exts);
 }
-reportModuleNotFoundToWatchMode(basePath,exts);
+reportModuleNotFoundToWatchMode(basePath,extensions);
 }
 
 returnfalse;

test/fixtures/require-resolve.js

@@ -98,3 +98,8 @@ assert.strictEqual(
 require.resolve('./printA.js',{}),
 require.resolve('./printA.js')
 );
+
+assert.strictEqual(
+require.resolve('no_index/'),
+path.join(__dirname,'node_modules','no_index','lib','index.js'),
+)