\Magento\Framework\Filesystem\Io\File::read() should be able to accept resource in second argument

lib/internal/Magento/Framework/Filesystem/Io/File.php

@@ -440,11 +440,16 @@ public function cd($dir)
      */
     public function read($filename, $dest = null)
     {
+        $result = false;
+
         $this->_cwd();
-        if ($dest !== null) {
-            $result = @copy($filename, $dest);
-        } else {
+        if ($dest === null) {
             $result = @file_get_contents($filename);
+        } elseif (is_resource($dest)) {
+            $result = @file_get_contents($filename);
+            fwrite($dest, $result);
+        } elseif (is_string($dest)) {
+            $result = @copy($filename, $dest);
         }
         $this->_iwd();
 

lib/internal/Magento/Framework/Filesystem/Test/Unit/Io/FileTest.php

@@ -0,0 +1,43 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+namespace Magento\Framework\Filesystem\Test\Unit\Io;
+
+use Magento\Framework\Exception\LocalizedException;
+use Magento\Framework\Filesystem\Io\File;
+use PHPUnit\Framework\TestCase;
+
+class FileTest extends TestCase
+{
+    private function getTmpDir()
+    {
+        $tmpDir = '/tmp/magento-' . \microtime(true);
+        if (!\file_exists($tmpDir)) {
+            \mkdir($tmpDir, 0777, true);
+        }
+        return $tmpDir;
+    }
+
+    /**
+     * To cover the issue on GitHub: #27866
+     * @throws LocalizedException
+     */
+    public function testReadShouldCopyTheSourceFileToTheGivenFileResource()
+    {
+        $content = \random_int(0, 1000);
+        $sourceFileName = "source-file.txt";
+        $tmpDir = $this->getTmpDir();
+        \file_put_contents("{$tmpDir}/{$sourceFileName}", $content);
+
+        $file = new File();
+        $targetFileName = "target-file.txt";
+        $targetFileHandle = \fopen("{$tmpDir}/{$targetFileName}", 'w');
+        $file->cd($tmpDir);
+        $file->read($sourceFileName, $targetFileHandle);
+
+        $targetContent = file_get_contents("{$tmpDir}/{$targetFileName}");
+        $this->assertEquals($content, $targetContent);
+    }
+}