Skip PhpParser\NodeTraverser in preload.php when it is already declared

[SanderMuller]

PHPStan Turbo declares a native PhpParser\NodeTraverser when it is activated. Rector has to activate it before preload.php runs, because Turbo cannot replace a class that is already declared. The plain require_once of php-parser's NodeTraverser.php in preload.php then fails with "Cannot redeclare class PhpParser\NodeTraverser".

build/build-preload.php now wraps that one line in if (! class_exists(NodeTraverser::class, false)), the same way the template already checks PHPStanTestCase. preload.php is regenerated with composer preload. Without Turbo the class is not declared yet, so preload.php loads it as before.

This prepares for loading Turbo in bin/rector.php. That part needs PHPStan 2.3.2, for phpstan/phpstan-src#6720. A proof of concept is on https://github.com/SanderMuller/rector-src/tree/turbo-poc.

I ran a cold bin/rector process --dry-run --clear-cache on rector-src itself, with 14 workers. It takes 8.2 s instead of 11.6 s, and 61 s of CPU instead of 100 s. Those are medians of 5 runs on an M4 Pro with PHP 8.5. The output is the same in all runs.

[TomasVotruba]

Thank you, can't wait to test this one 👍