[Filesystem] fix readlink() for Windows

[a1812]

Q	A
Branch?	4.4
Bug fix?	yes
New feature?	no
Deprecations?	no
Tickets
License	MIT
Doc PR

How to reproduce

Windows 10.0.19042.928, PHP 8.0.3, PHPUnit 9.5.4
run as Administrator
C:\php\php.exe ./phpunit --bootstrap ./vendor/autoload.php --configuration ./phpunit.xml.dist ./src/Symfony/Component/Filesystem/Tests

There were 2 failures:

1. Symfony\Component\Filesystem\Tests\FilesystemTest::testRemoveCleansInvalidLinks
   Failed asserting that 'C:\Users\albat\AppData\Local\Temp\1618836823.005.2057903605\directory\dir' is false.

D:\Z__PHP_PROJECT\symfony\src\Symfony\Component\Filesystem\Tests\FilesystemTest.php:379

2. Symfony\Component\Filesystem\Tests\FilesystemTest::testReadAbsoluteLink
   Failed asserting that two strings are equal.
   --- Expected
   +++ Actual
   @@ @@
   -'C:\Users\albat\AppData\Local\Temp\1618836823.1681.131301953\dir\link'
   +'C:\Users\albat\AppData\Local\Temp\1618836823.1681.131301953\file'

[a1812]

I'm not sure if skipping a test is a good idea, but the green bars clearly improve my mood :)

[nicolas-grekas]

:D
What changed in PHP 7.3? The Filesystem component is supposed to provide one consistent behavior for all versions and OSes. We might want to decide which behavior is the correct one and fix it.

[a1812]

What changed in PHP 7.3?

<?php

// check behavior functions realpath, readlink, and component Symfony Filesystem for windows

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

use Symfony\Component\Filesystem\Filesystem;

$dir = __DIR__ . DIRECTORY_SEPARATOR . 'dir';
mkdir($dir);

$file = $dir . DIRECTORY_SEPARATOR . 'file';
$link1 = $dir . DIRECTORY_SEPARATOR . 'link1';
$link2 = $dir . DIRECTORY_SEPARATOR . 'link2';

touch($file);

symlink($file, $link1);
symlink($link1, $link2);

$fs = new Filesystem();

echo 'PHP: ' . PHP_VERSION . PHP_EOL;
echo 'realpath: ' . realpath($link2) . PHP_EOL;
echo 'readlink: ' . readlink($link2) . PHP_EOL;
echo '$fs->readlink($link2, true): ' . $fs->readlink($link2, true) . PHP_EOL;
echo '$fs->readlink($link2): ' . $fs->readlink($link2) . PHP_EOL;

unlink($file);
unlink($link1);
unlink($link2);
rmdir($dir);

b - before patch, a - after patch

PHP	realpath	readlink	(b)$fs->readlink ($link2,true)	(b)$fs-> readlink ($link2)	(a)$fs->readlink ($link2,true)	(a)$fs->readlink ($link2)
8.0.*	file	link1	file	file	file	link1
7.4.18 - 7.4.10	file	link1	file	file	file	link1
7.4.9 - 7.4.0	link1	link1	file	link1	file	link1
7.3.28 - 7.3.22	file	file	file	file	file	file
7.3.21 - 7.3.2	link1	file	file	link1	file	link1
7.3.1 - 7.3.0	file	file	file	file	file	file
7.2.*	link1	file	file	link1	file	link1
7.1.3 - 7.1.33	link1	file	file	link1	file	link1

###conclusion:

• realpath() works correctly with PHP 7.4.10, bug report https://www.php.net/ChangeLog-7.php#PHP_7_4
• readlink() works correctly with PHP 7.4.0, bug report n/a

What to do with PHP 7.3.* ?

Correct me, maybe I am confusing or missing something.

[a1812]

how check

set PROJECT_DIR=C:\symfony
set PHPUNIT=%PROJECT_DIR%/phpunit^
    --colors=never^
    --bootstrap %PROJECT_DIR%/vendor\autoload.php^
    --configuration %PROJECT_DIR%/phpunit.xml.dist %PROJECT_DIR%/src/Symfony/Component/Filesystem

FOR %%V IN (
    7.1.3,
    7.1.33,
    7.2.15,
    7.2.34,
    7.3.0,
    7.3.15,
    7.3.27,
    7.3.28,
    7.4.0,
    7.4.9,
    7.4.10,
    7.4.15,
    7.4.16,
    7.4.18,
    8.0.0,
    8.0.1,
    8.0.2,
    8.0.3,
    8.0.5,
    8.0.6
) DO (
    c:\php\%%V\php %PHPUNIT%
    @if errorlevel 1 (
       exit /b
    )
)

[a1812]

Hi @nicolas-grekas, please check my code.

[a1812]

imho need to edit the description, the current one is misleading

"... On Windows systems, readlink() resolves recursively the children links of a link until a final target is found. ... "

https://symfony.com/doc/4.4/components/filesystem.html#readlink

[a1812]

Bug report for PHP7.3.27 https://bugs.php.net/bug.php?id=80993

[a1812]

Answer from php.net

The erroneous readlink() has apparently been fixed inadvertently
when php_sys_readlink() has been refactored[1].

Anyhow, PHP 7.3 is in security mode[2], so unless this would be
regarded as security issue, the fix will not be backported.

[1] <https://github.com/php/php-src/commit/91c905e83c338ef66da824be4f90c1d78d134507>
[2] <https://www.php.net/supported-versions.php>

I think we did everything we could (fixed for 8.0 and >=7.4.10) for behavior our component

[nicolas-grekas]

(what a mess :) )

[nicolas-grekas]

Thank you @a1812.