fs: readdir optionally returning type information

readdir and readdirSync now have a "withFileTypes" option, which, when
enabled, provides an array of DirectoryEntry objects, similar to Stats
objects, which have the filename and the type information.

Refs: #15699

PR-URL: #22020
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>

doc/api/fs.md

@@ -283,6 +283,92 @@ synchronous use libuv's threadpool, which can have surprising and negative
 performance implications for some applications. See the
 [`UV_THREADPOOL_SIZE`][] documentation for more information.
 
+## Class: fs.Dirent
+<!-- YAML
+added: REPLACEME
+-->
+
+When [`fs.readdir()`][] or [`fs.readdirSync()`][] is called with the
+`withFileTypes` option set to `true`, the resulting array is filled with
+`fs.Dirent` objects, rather than strings or `Buffers`.
+
+### dirent.isBlockDevice()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {boolean}
+
+Returns `true` if the `fs.Dirent` object describes a block device.
+
+### dirent.isCharacterDevice()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {boolean}
+
+Returns `true` if the `fs.Dirent` object describes a character device.
+
+### dirent.isDirectory()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {boolean}
+
+Returns `true` if the `fs.Dirent` object describes a file system
+directory.
+
+### dirent.isFIFO()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {boolean}
+
+Returns `true` if the `fs.Dirent` object describes a first-in-first-out
+(FIFO) pipe.
+
+### dirent.isFile()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {boolean}
+
+Returns `true` if the `fs.Dirent` object describes a regular file.
+
+### dirent.isSocket()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {boolean}
+
+Returns `true` if the `fs.Dirent` object describes a socket.
+
+### dirent.isSymbolicLink()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {boolean}
+
+Returns `true` if the `fs.Dirent` object describes a symbolic link.
+
+
+### dirent.name
+<!-- YAML
+added: REPLACEME
+-->
+
+* {string|Buffer}
+
+The file name that this `fs.Dirent` object refers to. The type of this
+value is determined by the `options.encoding` passed to [`fs.readdir()`][] or
+[`fs.readdirSync()`][].
+
 ## Class: fs.FSWatcher
 <!-- YAML
 added: v0.5.8
@@ -2299,9 +2385,10 @@ changes:
 * `path` {string|Buffer|URL}
 * `options` {string|Object}
   * `encoding` {string} **Default:** `'utf8'`
+  * `withFileTypes` {boolean} **Default:** `false`
 * `callback` {Function}
   * `err` {Error}
-  * `files` {string[]|Buffer[]}
+  * `files` {string[]|Buffer[]|fs.Dirent[]}
 
 Asynchronous readdir(3). Reads the contents of a directory.
 The callback gets two arguments `(err, files)` where `files` is an array of
@@ -2312,6 +2399,9 @@ object with an `encoding` property specifying the character encoding to use for
 the filenames passed to the callback. If the `encoding` is set to `'buffer'`,
 the filenames returned will be passed as `Buffer` objects.
 
+If `options.withFileTypes` is set to `true`, the `files` array will contain
+[`fs.Dirent`][] objects.
+
 ## fs.readdirSync(path[, options])
 <!-- YAML
 added: v0.1.21
@@ -2325,7 +2415,8 @@ changes:
 * `path` {string|Buffer|URL}
 * `options` {string|Object}
   * `encoding` {string} **Default:** `'utf8'`
-* Returns: {string[]} An array of filenames excluding `'.'` and `'..'`.
+  * `withFileTypes` {boolean} **Default:** `false`
+* Returns: {string[]|Buffer[]|fs.Dirent[]}
 
 Synchronous readdir(3).
 
@@ -2334,6 +2425,9 @@ object with an `encoding` property specifying the character encoding to use for
 the filenames returned. If the `encoding` is set to `'buffer'`,
 the filenames returned will be passed as `Buffer` objects.
 
+If `options.withFileTypes` is set to `true`, the result will contain
+[`fs.Dirent`][] objects.
+
 ## fs.readFile(path[, options], callback)
 <!-- YAML
 added: v0.1.29
@@ -4611,6 +4705,7 @@ the file contents.
 [`WriteStream`]: #fs_class_fs_writestream
 [`EventEmitter`]: events.html
 [`event ports`]: http://illumos.org/man/port_create
+[`fs.Dirent`]: #fs_class_fs_dirent
 [`fs.FSWatcher`]: #fs_class_fs_fswatcher
 [`fs.Stats`]: #fs_class_fs_stats
 [`fs.access()`]: #fs_fs_access_path_mode_callback
@@ -4626,6 +4721,8 @@ the file contents.
 [`fs.mkdtemp()`]: #fs_fs_mkdtemp_prefix_options_callback
 [`fs.open()`]: #fs_fs_open_path_flags_mode_callback
 [`fs.read()`]: #fs_fs_read_fd_buffer_offset_length_position_callback
+[`fs.readdir()`]: #fs_fs_readdir_path_options_callback
+[`fs.readdirSync()`]: #fs_fs_readdirsync_path_options
 [`fs.readFile()`]: #fs_fs_readfile_path_options_callback
 [`fs.readFileSync()`]: #fs_fs_readfilesync_path_options
 [`fs.realpath()`]: #fs_fs_realpath_path_options_callback

lib/fs.js

@@ -58,6 +58,8 @@ const { getPathFromURL } = require('internal/url');
 const internalUtil = require('internal/util');
 const {
   copyObject,
+  Dirent,
+  getDirents,
   getOptions,
   nullCheck,
   preprocessSymlinkDestination,
@@ -736,8 +738,19 @@ function readdir(path, options, callback) {
   validatePath(path);
 
   const req = new FSReqWrap();
-  req.oncomplete = callback;
-  binding.readdir(pathModule.toNamespacedPath(path), options.encoding, req);
+  if (!options.withFileTypes) {
+    req.oncomplete = callback;
+  } else {
+    req.oncomplete = (err, result) => {
+      if (err) {
+        callback(err);
+        return;
+      }
+      getDirents(path, result, callback);
+    };
+  }
+  binding.readdir(pathModule.toNamespacedPath(path), options.encoding,
+                  !!options.withFileTypes, req);
 }
 
 function readdirSync(path, options) {
@@ -746,9 +759,10 @@ function readdirSync(path, options) {
   validatePath(path);
   const ctx = { path };
   const result = binding.readdir(pathModule.toNamespacedPath(path),
-                                 options.encoding, undefined, ctx);
+                                 options.encoding, !!options.withFileTypes,
+                                 undefined, ctx);
   handleErrorFromBinding(ctx);
-  return result;
+  return options.withFileTypes ? getDirents(path, result) : result;
 }
 
 function fstat(fd, options, callback) {
@@ -1773,6 +1787,7 @@ module.exports = fs = {
   writeFileSync,
   write,
   writeSync,
+  Dirent,
   Stats,
 
   // Stream constructors

lib/internal/fs/promises.js

@@ -18,6 +18,7 @@ const { getPathFromURL } = require('internal/url');
 const { isUint8Array } = require('internal/util/types');
 const {
   copyObject,
+  getDirents,
   getOptions,
   getStatsFromBinding,
   nullCheck,
@@ -36,10 +37,13 @@ const {
   validateUint32
 } = require('internal/validators');
 const pathModule = require('path');
+const { promisify } = require('internal/util');
 
 const kHandle = Symbol('handle');
 const { kUsePromises } = binding;
 
+const getDirectoryEntriesPromise = promisify(getDirents);
+
 class FileHandle {
   constructor(filehandle) {
     this[kHandle] = filehandle;
@@ -294,8 +298,12 @@ async function readdir(path, options) {
   options = getOptions(options, {});
   path = getPathFromURL(path);
   validatePath(path);
-  return binding.readdir(pathModule.toNamespacedPath(path),
-                         options.encoding, kUsePromises);
+  const result = await binding.readdir(pathModule.toNamespacedPath(path),
+                                       options.encoding, !!options.withTypes,
+                                       kUsePromises);
+  return options.withFileTypes ?
+    getDirectoryEntriesPromise(path, result) :
+    result;
 }
 
 async function readlink(path, options) {

lib/internal/fs/utils.js

@@ -12,6 +12,8 @@ const {
 const { isUint8Array } = require('internal/util/types');
 const pathModule = require('path');
 const util = require('util');
+const kType = Symbol('type');
+const kStats = Symbol('stats');
 
 const {
   O_APPEND,
@@ -31,24 +33,135 @@ const {
   S_IFREG,
   S_IFSOCK,
   UV_FS_SYMLINK_DIR,
-  UV_FS_SYMLINK_JUNCTION
+  UV_FS_SYMLINK_JUNCTION,
+  UV_DIRENT_UNKNOWN,
+  UV_DIRENT_FILE,
+  UV_DIRENT_DIR,
+  UV_DIRENT_LINK,
+  UV_DIRENT_FIFO,
+  UV_DIRENT_SOCKET,
+  UV_DIRENT_CHAR,
+  UV_DIRENT_BLOCK
 } = process.binding('constants').fs;
 
 const isWindows = process.platform === 'win32';
 
+let fs;
+function lazyLoadFs() {
+  if (!fs) {
+    fs = require('fs');
+  }
+  return fs;
+}
+
 function assertEncoding(encoding) {
   if (encoding && !Buffer.isEncoding(encoding)) {
     throw new ERR_INVALID_OPT_VALUE_ENCODING(encoding);
   }
 }
 
+class Dirent {
+  constructor(name, type) {
+    this.name = name;
+    this[kType] = type;
+  }
+
+  isDirectory() {
+    return this[kType] === UV_DIRENT_DIR;
+  }
+
+  isFile() {
+    return this[kType] === UV_DIRENT_FILE;
+  }
+
+  isBlockDevice() {
+    return this[kType] === UV_DIRENT_BLOCK;
+  }
+
+  isCharacterDevice() {
+    return this[kType] === UV_DIRENT_CHAR;
+  }
+
+  isSymbolicLink() {
+    return this[kType] === UV_DIRENT_LINK;
+  }
+
+  isFIFO() {
+    return this[kType] === UV_DIRENT_FIFO;
+  }
+
+  isSocket() {
+    return this[kType] === UV_DIRENT_SOCKET;
+  }
+}
+
+class DirentFromStats extends Dirent {
+  constructor(name, stats) {
+    super(name, null);
+    this[kStats] = stats;
+  }
+}
+
+for (const name of Reflect.ownKeys(Dirent.prototype)) {
+  if (name === 'constructor') {
+    continue;
+  }
+  DirentFromStats.prototype[name] = function() {
+    return this[kStats][name]();
+  };
+}
+
 function copyObject(source) {
   var target = {};
   for (var key in source)
     target[key] = source[key];
   return target;
 }
 
+function getDirents(path, [names, types], callback) {
+  var i;
+  if (typeof callback == 'function') {
+    const len = names.length;
+    let toFinish = 0;
+    for (i = 0; i < len; i++) {
+      const type = types[i];
+      if (type === UV_DIRENT_UNKNOWN) {
+        const name = names[i];
+        const idx = i;
+        toFinish++;
+        lazyLoadFs().stat(pathModule.resolve(path, name), (err, stats) => {
+          if (err) {
+            callback(err);
+            return;
+          }
+          names[idx] = new DirentFromStats(name, stats);
+          if (--toFinish === 0) {
+            callback(null, names);
+          }
+        });
+      } else {
+        names[i] = new Dirent(names[i], types[i]);
+      }
+    }
+    if (toFinish === 0) {
+      callback(null, names);
+    }
+  } else {
+    const len = names.length;
+    for (i = 0; i < len; i++) {
+      const type = types[i];
+      if (type === UV_DIRENT_UNKNOWN) {
+        const name = names[i];
+        const stats = lazyLoadFs().statSync(pathModule.resolve(path, name));
+        names[i] = new DirentFromStats(name, stats);
+      } else {
+        names[i] = new Dirent(names[i], types[i]);
+      }
+    }
+    return names;
+  }
+}
+
 function getOptions(options, defaultOptions) {
   if (options === null || options === undefined ||
       typeof options === 'function') {
@@ -341,6 +454,8 @@ function validatePath(path, propName = 'path') {
 module.exports = {
   assertEncoding,
   copyObject,
+  Dirent,
+  getDirents,
   getOptions,
   nullCheck,
   preprocessSymlinkDestination,