Infinite recursion when recursive / self-referencing arrays are checked whether they contain only scalar values

[ptomulik]

Q	A
PHPUnit version	>= 10.4.0
PHP version	8.2
Installation Method	composer

Summary

Current behavior

Tests such as the following end with segmentation fault when run with PHPUnit >= 10.4:

<?php declare(strict_types=1);                                                                                          
                                                                                                                        
use PHPUnit\Framework\TestCase;                                                                                         
                                                                                                                        
final class ExporterTest extends TestCase                                                                               
{                                                                                                                       
    public function testAnythingThatFailsWithRecursiveArray(): void                                                     
    {                                                                                                                   
        $array = [];                                                                                             
        $array['self'] = &$array;                                                                                       
                                                                                                                        
        $this->assertFalse($array);                                                                                     
    }                                                                                                                   
}                                                                                                                       

Here is the run result:

ptomulik@barakus:$ XDEBUG_MODE=coverage vendor/bin/phpunit
PHPUnit 10.4.0 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.2.12
Configuration: /tmp/phpunit-issue/phpunit.xml

Segmentation fault (core dumped)

With Xdebug enabled I get this:

1) ExporterTest::testAnythingThatFailsWithRecursiveArray
Error: Xdebug has detected a possible infinite loop, and aborted your script with a stack depth of '256' frames

How to reproduce

Run a test that is expected to fail and involves a recursive array (see above).

Expected behavior

Shall report failure, as follows (PHPUnit 10.3 does this correctly):

ptomulik@barakus:$ XDEBUG_MODE=coverage vendor/bin/phpunit
PHPUnit 10.3.0 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.2.12
Configuration: /tmp/phpunit-issue/phpunit.xml

F                                                                   1 / 1 (100%)

Time: 00:00.012, Memory: 8.00 MB

There was 1 failure:

1) ExporterTest::testAnythingThatFailsWithRecursiveArray
Failed asserting that Array &0 [
    'self' => Array &1 [
        'self' => Array &1,
    ],
] is false.

/tmp/phpunit-issue/tests/ExporterTest.php:12

FAILURES!
Tests: 1, Assertions: 1, Failures: 1.

Suggestions

There were changes around exporter stuff between PHPUnit 10.3 and 10.4. I guess the root cause of this is the new method PHPUnit\Util\Exporter::isScalarOrArrayOfScalars(). Perhaps it shall use recursion context similarly to all the recursive methods of SebastianBergman\Exporter\Exporter.

[ptomulik]

Anyway,

$array = [];                                                                                             
$array['self'] = &$array;

the output for the above array is also wrong:

1) ExporterTest::testAnythingThatFailsWithRecursiveArray
Failed asserting that Array &0 [
    'self' => Array &1 [
        'self' => Array &1,
    ],
] is false.

I'd rather expect just:

1) ExporterTest::testAnythingThatFailsWithRecursiveArray
Failed asserting that Array &0 [
   'self' => Array &0,
] is false.

But this is actually Exporter's issue.

[ptomulik]

Hi,

is it worth to be work on?

I've actually attempted to help with this in #5569, but it was suddenly closed.