Symfony version(s) affected: 5.2.0

Description

Usage of Symfony\Component\Filesystem\Filesystem::dumpFile failes on Windows when trying to dump e.g. into the personal downloads directory under C:\Users\*\Downloads due to failing of the writeability check for the target folder even though an actual write succeeds.

How to reproduce

<?php

require_once __DIR__ . '/vendor/autoload.php';

$targetFilePath = 'C:/Users/*user*/Downloads/file.ext';

var_dump(is_writable(dirname($targetFilePath))); // bool(false)
var_dump(file_put_contents($targetFilePath, 'foo') !== false); // bool(true)

$filesystem = new Symfony\Component\Filesystem\Filesystem();
$filesystem->dumpFile($targetFilePath, 'bar'); // exception

Possible Solution

Is more of an upstream-problem with PHP's implementation of is_writable (see e.g. https://bugs.php.net/bug.php?id=68926) but it might make sense to just skip the check on Windows to provide a fix within the symfony component.

The root cause is probably the Microsoft Universal Windows Platform app security model.

Additional context

Testing on Windows 10 1904 with

PHP 7.4.12 (cli) (built: Oct 27 2020 17:18:47) ( ZTS Visual C++ 2017 x64 )
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