[Docs] Add docs for troubleshoot preload conflict on phpunit 12+

[samsonasik]

@ostrolucky @TomasVotruba this is new documentation section for troubleshooting preload conflict on phpunit 12+

Ref

• PHP Fatal error: Cannot declare interface PhpParser\NodeVisitor, because the name is already in use in vendor/rector/rector/vendor/nikic/php-parser/lib/PhpParser/NodeVisitor.php on line 6 rector#9242
• chore!: handle conflict phpunit 12+ conflict preload with rector ostrolucky/rector-rules#44

[samsonasik]

All checks have passed 🎉 @TomasVotruba I think it is ready.

[TomasVotruba]

This look a bit hacky. What is the change in PHPUnit 12 that caused this?

[ostrolucky]

Unfortunately it seems this change breaks phpstan https://github.com/ostrolucky/rector-rules/actions/runs/16016236306/job/45187044734?pr=44

[samsonasik]

I am not sure to be honest, but these 2 lines for too early load is shown here:

• https://github.com/sebastianbergmann/phpunit/blob/7c2e0781d70a2455041ef7e26c46b37bd558b3df/phpunit#L46
• https://github.com/sebastianbergmann/phpunit/blob/7c2e0781d70a2455041ef7e26c46b37bd558b3df/phpunit#L72

even without setup phpunit bootstrap, it will always load vendor/autoload.php too early.

That happen only on phpunit 12+, with php 8.3+, so either it phpunit issue, or php 8.3 changed behaviour.

[samsonasik]

@ostrolucky in seems in rector preload.php, it needs initialized:

if (defined('__PHPSTAN_RUNNING__')) {
    return;
}

I will create PR for that.

[samsonasik]

@ostrolucky I created PR:

• Add check phpstan if phpstan is running on preload.php rector-src#7040

for that, it seems not ideal, but that's what I can think of right now.

[samsonasik]

@TomasVotruba let's merge this, so it sync with PR:

• Add check phpstan if phpstan is running on preload.php rector-src#7040