`Uncaught Error: Typed property RectorPrefix202512\Symplify\EasyParallel\ValueObject\ParallelProcess::$encoder must not be accessed before initialization`

[devnix]

Hi! I'm frequently getting the following stacktrace when running Rector on a big project, it happens sometimes on the first half of the process if there is no previous cache:

PHP Fatal error:  Uncaught Error: Typed property RectorPrefix202512\Symplify\EasyParallel\ValueObject\ParallelProcess::$encoder must not be accessed before initialization in [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ParallelProcess.php:108
Stack trace:
#0 [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ProcessPool.php(48): RectorPrefix202512\Symplify\EasyParallel\ValueObject\ParallelProcess->quit()
#1 [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ProcessPool.php(58): RectorPrefix202512\Symplify\EasyParallel\ValueObject\ProcessPool->quitProcess()
#2 [...]/vendor/rector/rector/src/Parallel/Application/ParallelFileProcessor.php(107): RectorPrefix202512\Symplify\EasyParallel\ValueObject\ProcessPool->quitAll()
#3 [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ParallelProcess.php(96): Rector\Parallel\Application\ParallelFileProcessor->Rector\Parallel\Application\{closure}()
#4 [...]/vendor/rector/rector/vendor/react/event-loop/src/Timer/Timers.php(86): RectorPrefix202512\Symplify\EasyParallel\ValueObject\ParallelProcess->RectorPrefix202512\Symplify\EasyParallel\ValueObject\{closure}()
#5 [...]/vendor/rector/rector/vendor/react/event-loop/src/StreamSelectLoop.php(150): RectorPrefix202512\React\EventLoop\Timer\Timers->tick()
#6 [...]/vendor/rector/rector/src/Parallel/Application/ParallelFileProcessor.php(185): RectorPrefix202512\React\EventLoop\StreamSelectLoop->run()
#7 [...]/vendor/rector/rector/src/Application/ApplicationFileProcessor.php(234): Rector\Parallel\Application\ParallelFileProcessor->process()
#8 [...]/vendor/rector/rector/src/Application/ApplicationFileProcessor.php(126): Rector\Application\ApplicationFileProcessor->runParallel()
#9 [...]/vendor/rector/rector/src/Console/Command/ProcessCommand.php(172): Rector\Application\ApplicationFileProcessor->run()
#10 [...]/vendor/rector/rector/vendor/symfony/console/Command/Command.php(289): Rector\Console\Command\ProcessCommand->execute()
#11 [...]/vendor/rector/rector/vendor/symfony/console/Application.php(892): RectorPrefix202512\Symfony\Component\Console\Command\Command->run()
#12 [...]/vendor/rector/rector/vendor/symfony/console/Application.php(279): RectorPrefix202512\Symfony\Component\Console\Application->doRunCommand()
#13 [...]/vendor/rector/rector/src/Console/ConsoleApplication.php(60): RectorPrefix202512\Symfony\Component\Console\Application->doRun()
#14 [...]/vendor/rector/rector/vendor/symfony/console/Application.php(162): Rector\Console\ConsoleApplication->doRun()
#15 [...]/vendor/rector/rector/bin/rector.php(130): RectorPrefix202512\Symfony\Component\Console\Application->run()
#16 [...]/vendor/rector/rector/bin/rector(5): require_once('...')
#17 [...]/vendor/bin/rector(119): include('...')
#18 {main}
  thrown in [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ParallelProcess.php on line 108
Fatal error: Uncaught Error: Typed property RectorPrefix202512\Symplify\EasyParallel\ValueObject\ParallelProcess::$encoder must not be accessed before initialization in [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ParallelProcess.php:108
Stack trace:
#0 [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ProcessPool.php(48): RectorPrefix202512\Symplify\EasyParallel\ValueObject\ParallelProcess->quit()
#1 [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ProcessPool.php(58): RectorPrefix202512\Symplify\EasyParallel\ValueObject\ProcessPool->quitProcess()
#2 [...]/vendor/rector/rector/src/Parallel/Application/ParallelFileProcessor.php(107): RectorPrefix202512\Symplify\EasyParallel\ValueObject\ProcessPool->quitAll()
#3 [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ParallelProcess.php(96): Rector\Parallel\Application\ParallelFileProcessor->Rector\Parallel\Application\{closure}()
#4 [...]/vendor/rector/rector/vendor/react/event-loop/src/Timer/Timers.php(86): RectorPrefix202512\Symplify\EasyParallel\ValueObject\ParallelProcess->RectorPrefix202512\Symplify\EasyParallel\ValueObject\{closure}()
#5 [...]/vendor/rector/rector/vendor/react/event-loop/src/StreamSelectLoop.php(150): RectorPrefix202512\React\EventLoop\Timer\Timers->tick()
#6 [...]/vendor/rector/rector/src/Parallel/Application/ParallelFileProcessor.php(185): RectorPrefix202512\React\EventLoop\StreamSelectLoop->run()
#7 [...]/vendor/rector/rector/src/Application/ApplicationFileProcessor.php(234): Rector\Parallel\Application\ParallelFileProcessor->process()
#8 [...]/vendor/rector/rector/src/Application/ApplicationFileProcessor.php(126): Rector\Application\ApplicationFileProcessor->runParallel()
#9 [...]/vendor/rector/rector/src/Console/Command/ProcessCommand.php(172): Rector\Application\ApplicationFileProcessor->run()
#10 [...]/vendor/rector/rector/vendor/symfony/console/Command/Command.php(289): Rector\Console\Command\ProcessCommand->execute()
#11 [...]/vendor/rector/rector/vendor/symfony/console/Application.php(892): RectorPrefix202512\Symfony\Component\Console\Command\Command->run()
#12 [...]/vendor/rector/rector/vendor/symfony/console/Application.php(279): RectorPrefix202512\Symfony\Component\Console\Application->doRunCommand()
#13 [...]/vendor/rector/rector/src/Console/ConsoleApplication.php(60): RectorPrefix202512\Symfony\Component\Console\Application->doRun()
#14 [...]/vendor/rector/rector/vendor/symfony/console/Application.php(162): Rector\Console\ConsoleApplication->doRun()
#15 [...]/vendor/rector/rector/bin/rector.php(130): RectorPrefix202512\Symfony\Component\Console\Application->run()
#16 [...]/vendor/rector/rector/bin/rector(5): require_once('...')
#17 [...]/vendor/bin/rector(119): include('...')
#18 {main}
  thrown in [...]/vendor/rector/rector/vendor/symplify/easy-parallel/src/ValueObject/ParallelProcess.php on line 108

In my installation, the ParallelProcess.php:108 line corresponds to $this->encoder->end(), which seems like there's some kind of race condition where the subprocess is being closed before binding the connection.

I've been looking forward to making a contribution, but I can't come with a good decision without asking you: making the attribute nullable only feels like a little band aid, but a better solution would drastically change the API of ParallelProcess.

I wish I could show a reproducer, but it's happening on a private project and on an inconsistent basis, but I think the problem is very located here

[TomasVotruba]

Thanks for reaching out. I've seen this error before, many years ago, but not sure where it lead us.
Making the property nullable, would fix this particular error, but it would allow call on null where object should be.

Seems like bindConnection() is not happening where it should be. Maybe placing var_dump() around its calls might give us more intel.

It might be also released to some Symfony or other var dumper. I vaguely recall, that in case of error, Symfony tried to dump stack trace and it fails on such a property.

Another idea is to put a tracking function to log all data known in quitProcess(). More information might help there.

[devnix]

I'll try to replicate it later with some dumping around.

Making the property nullable, would fix this particular error, but it would allow call on null where object should be.

That's what I thought so, but anyways the $this->encoder->write($data) line is also unsafe as the attribute is not being set on the constructor.

Right now I trace the error to this block, where $this->processPool->quitAll() crashes, $throwable contains a Child process timed out after 240 seconds.

I've indeed lowered the job size and doubled the timeout.

[devnix]

I'm out of ideas. I think that a process with a connection is being killed and respawned at $this->processPool->quitProcess($processIdentifier), and then $this->processPool->quitAll() closes all subprocesses, being the case that at least one of them didn't had any connection binded, which looks like it's a very valid case.

I would advocate for making the encoder nullable, and adding a sanity check at $this->encoder->write($data) (You cannot send a request without binding a connection previously), or change the API and add a Connection or Pipe value object, which would be safer in terms of typing and usage