fs: fix readdir recursive sync & callback

lib/fs.js

@@ -1437,14 +1437,21 @@ function readdirSyncRecursive(basePath, options) {
     );
     handleErrorFromBinding(ctx);
 
-    for (let i = 0; i < readdirResult.length; i++) {
-      if (withFileTypes) {
+    if (withFileTypes) {
+      // Calling `readdir` with `withFileTypes=true`, the result is an array of arrays.
+      // The first array is the names, and the second array is the types.
+      // They are guaranteed to be the same length; hence, setting `length` to the length
+      // of the first array within the result.
+      const length = readdirResult[0].length;
+      for (let i = 0; i < length; i++) {
         const dirent = getDirent(path, readdirResult[0][i], readdirResult[1][i]);
         ArrayPrototypePush(readdirResults, dirent);
         if (dirent.isDirectory()) {
           ArrayPrototypePush(pathsQueue, pathModule.join(dirent.path, dirent.name));
         }
-      } else {
+      }
+    } else {
+      for (let i = 0; i < readdirResult.length; i++) {
         const resultPath = pathModule.join(path, readdirResult[i]);
         const relativeResultPath = pathModule.relative(basePath, resultPath);
         const stat = binding.internalModuleStat(resultPath);

test/sequential/test-fs-readdir-recursive.js

@@ -131,9 +131,11 @@ function getDirentPath(dirent) {
 }
 
 function assertDirents(dirents) {
+  assert.strictEqual(dirents.length, expected.length);
   dirents.sort((a, b) => (getDirentPath(a) < getDirentPath(b) ? -1 : 1));
   for (const [i, dirent] of dirents.entries()) {
     assert(dirent instanceof fs.Dirent);
+    assert.notStrictEqual(dirent.name, undefined);
     assert.strictEqual(getDirentPath(dirent), expected[i]);
   }
 }