From d25d82ad912eed90af6a9d05cba1e62c856f9295 Mon Sep 17 00:00:00 2001
From: Mohamed Emad <8965415+TheGeekyM@users.noreply.github.com>
Date: Fri, 6 Nov 2026 08:21:05 +0200
Subject: [PATCH] Use fs.constants.F_OK in checkRequiredFiles

---
<!--
Thank you for sending the PR!
---
 .../__tests__/checkRequiredFiles.test.js      | 112 ++++++++++++++++++
 .../react-dev-utils/checkRequiredFiles.js     |   2 +-
 2 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100644 packages/react-dev-utils/__tests__/checkRequiredFiles.test.js

diff --git a/packages/react-dev-utils/__tests__/checkRequiredFiles.test.js b/packages/react-dev-utils/__tests__/checkRequiredFiles.test.js
new file mode 100644
index 00000000000..703512f8b17
--- /dev/null
+++ b/packages/react-dev-utils/__tests__/checkRequiredFiles.test.js
@@ -0,0 +1,112 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+const checkRequiredFiles = require('../checkRequiredFiles');
+
+describe('checkRequiredFiles', () => {
+  let tmpDir;
+  let logSpy;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'check-required-files-'));
+    logSpy = jest.spyOn(console, 'log').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  function createFile(name) {
+    const filePath = path.join(tmpDir, name);
+    fs.writeFileSync(filePath, '');
+    return filePath;
+  }
+
+  it('returns true when all files exist', () => {
+    const files = [createFile('index.html'), createFile('index.js')];
+
+    expect(checkRequiredFiles(files)).toBe(true);
+    expect(logSpy).not.toHaveBeenCalled();
+  });
+
+  it('returns true for an empty list', () => {
+    expect(checkRequiredFiles([])).toBe(true);
+    expect(logSpy).not.toHaveBeenCalled();
+  });
+
+  it('returns false when a file is missing', () => {
+    const files = [createFile('index.html'), path.join(tmpDir, 'missing.js')];
+
+    expect(checkRequiredFiles(files)).toBe(false);
+  });
+
+  it('logs the name and directory of the first missing file', () => {
+    const missing = path.join(tmpDir, 'missing.js');
+    const files = [
+      createFile('index.html'),
+      missing,
+      path.join(tmpDir, 'other.js'),
+    ];
+
+    checkRequiredFiles(files);
+
+    const output = logSpy.mock.calls.map(args => args.join(' ')).join('\n');
+    expect(output).toContain('Could not find a required file.');
+    expect(output).toContain('missing.js');
+    expect(output).toContain(tmpDir);
+    expect(output).not.toContain('other.js');
+  });
+
+  it('checks existence using fs.constants.F_OK', () => {
+    const accessSpy = jest.spyOn(fs, 'accessSync');
+    const file = createFile('index.js');
+
+    checkRequiredFiles([file]);
+
+    expect(accessSpy).toHaveBeenCalledTimes(1);
+    expect(accessSpy).toHaveBeenCalledWith(file, fs.constants.F_OK);
+    expect(typeof accessSpy.mock.calls[0][1]).toBe('number');
+  });
+
+  it('does not rely on the deprecated fs.F_OK alias', () => {
+    // Current Node releases define `fs.F_OK` as non-configurable (or drop it
+    // entirely), so it cannot be redefined on the real module. Instead, load
+    // the module against an `fs` whose `F_OK` alias is unavailable.
+    const accessSpy = jest.spyOn(fs, 'accessSync');
+    let isolatedCheckRequiredFiles;
+
+    jest.isolateModules(() => {
+      jest.doMock('fs', () => {
+        const fsWithoutAlias = Object.create(fs);
+        Object.defineProperty(fsWithoutAlias, 'F_OK', {
+          configurable: true,
+          get() {
+            return undefined;
+          },
+        });
+        return fsWithoutAlias;
+      });
+      isolatedCheckRequiredFiles = require('../checkRequiredFiles');
+    });
+
+    try {
+      const file = createFile('index.js');
+      expect(isolatedCheckRequiredFiles([file])).toBe(true);
+      expect(accessSpy).toHaveBeenCalledTimes(1);
+      expect(accessSpy.mock.calls[0][1]).toBe(fs.constants.F_OK);
+      expect(accessSpy.mock.calls[0][1]).not.toBeUndefined();
+    } finally {
+      jest.dontMock('fs');
+    }
+  });
+});
diff --git a/packages/react-dev-utils/checkRequiredFiles.js b/packages/react-dev-utils/checkRequiredFiles.js
index 9799cf6b590..3293818cd66 100644
--- a/packages/react-dev-utils/checkRequiredFiles.js
+++ b/packages/react-dev-utils/checkRequiredFiles.js
@@ -16,7 +16,7 @@ function checkRequiredFiles(files) {
   try {
     files.forEach(filePath => {
       currentFilePath = filePath;
-      fs.accessSync(filePath, fs.F_OK);
+      fs.accessSync(filePath, fs.constants.F_OK);
     });
     return true;
   } catch (err) {