Enhancing PhpStan's capabilities through an extension (container singleton)

[gnutix]

Hello there,

I am working on a big legacy project which uses a singleton container Container::getInstance() which implements ArrayAccess to fetch some services, like $someValue = Container::getInstance()['someService']->someMethod($argument1, $argument2);. Currently, even if the method someMethod() is properly typed (like someMethod(string $argument1, bool $argument2), PHPStan will not be able to detect that we mess up the arguments we gave (say we inversed them).

I'm wondering if there would be a way to develop a plugin that would allow PhpStan to recognize "Container::getInstance()" calls, track whether it is followed immediately by an array access or the variable on which it's stored, and complete the inspections with the parsing of the Container.php file which defines all the indexed and the services' types.

WDYT ? Is that even remotely possible ? Or is the only solution to add /** @var SomeService $someService */ and make sure it's never used directly through array access ?

Thanks for your insights.
gnutix

[ondrejmirtes]

Hi, to describe what's returned by Container::getInstance()['someService'], you can write a dynamic return type extension for ArrayAccess::offsetGet() method (where ArrayAccess should be narrowed by the type returned by Container::getInstance()).

It specifically works thanks to this piece of code: https://github.com/phpstan/phpstan-src/blob/0af0399a9c877b3a40a8ad89f62b623c87538a90/src/Analyser/MutatingScope.php#L2165-L2175

There's already a similar extension: https://github.com/phpstan/phpstan-nette/blob/master/src/Type/Nette/ComponentModelArrayAccessDynamicReturnTypeExtension.php

What it does:

Nette's component model allows $container->getComponent('name') to be shortened as $container['name']. The method looks at createComponentName() method on the same object and its return type, and uses that as the type returned by $container['name'].

[gnutix]

Thanks a lot for your detailed answer. I finally managed to dedicate some time to this task and succeeded in implementing such an extension. 🤗

[ondrejmirtes]

Cool 😊