fs: make mutating options in Promises readdir() not affect results

PR-URL: #56057
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/fs/promises.js

@@ -944,6 +944,10 @@ async function readdirRecursive(originalPath, options) {
 
 async function readdir(path, options) {
   options = getOptions(options);
+
+  // Make shallow copy to prevent mutating options from affecting results
+  options = copyObject(options);
+
   path = getValidatedPath(path);
   if (options.recursive) {
     return readdirRecursive(path, options);

test/parallel/test-fs-readdir-types.js

@@ -78,6 +78,14 @@ fs.readdir(readdirDir, {
   assertDirents(dirents);
 })().then(common.mustCall());
 
+// Check that mutating options doesn't affect results
+(async () => {
+  const options = { withFileTypes: true };
+  const direntsPromise = fs.promises.readdir(readdirDir, options);
+  options.withFileTypes = false;
+  assertDirents(await direntsPromise);
+})().then(common.mustCall());
+
 // Check for correct types when the binding returns unknowns
 const UNKNOWN = constants.UV_DIRENT_UNKNOWN;
 const oldReaddir = binding.readdir;