fs: export constants from fs/promises

Author: F3n67u

doc/api/fs.md

@@ -789,8 +789,7 @@ with an {Error} object. The following example checks if the file
 `/etc/passwd` can be read and written by the current process.
 
 ```mjs
-import { access } from 'node:fs/promises';
-import { constants } from 'node:fs';
+import { access, constants } from 'node:fs/promises';
 
 try {
   await access('/etc/passwd', constants.R_OK | constants.W_OK);
@@ -892,8 +891,7 @@ error occurs after the destination file has been opened for writing, an attempt
 will be made to remove the destination.
 
 ```mjs
-import { constants } from 'node:fs';
-import { copyFile } from 'node:fs/promises';
+import { copyFile, constants } from 'node:fs/promises';
 
 try {
   await copyFile('source.txt', 'destination.txt');

lib/internal/fs/promises.js

@@ -17,13 +17,15 @@ const {
   Uint8Array,
 } = primordials;
 
+const { fs: constants } = internalBinding('constants');
 const {
   F_OK,
   O_SYMLINK,
   O_WRONLY,
   S_IFMT,
   S_IFREG
-} = internalBinding('constants').fs;
+} = constants;
+
 const binding = internalBinding('fs');
 const { Buffer } = require('buffer');
 
@@ -899,6 +901,7 @@ module.exports = {
     appendFile,
     readFile,
     watch,
+    constants,
   },
 
   FileHandle,

test/parallel/test-fs-promises-exists.js

@@ -2,5 +2,8 @@
 
 require('../common');
 const assert = require('assert');
+const fs = require('fs');
+const fsPromises = require('fs/promises');
 
-assert.strictEqual(require('fs/promises'), require('fs').promises);
+assert.strictEqual(fsPromises, fs.promises);
+assert.strictEqual(fsPromises.constants, fs.constants);