Phpstan ignores possibly undefined array offsets

[ptomulik]

Bug report

The following code should raise an error, but it passes with level 9 + strict rules.

Code snippet that reproduces the problem

<?php declare(strict_types = 1);

/**
 * @param array<mixed> $array
 * @return mixed
 */
function foo(array $array) {
	return $array['foo'];
}

https://phpstan.org/r/5347b67e-f0ad-4505-aeca-cfb074dcb3e7

Expected output

It should raise an error about possibly undefined array offset, same way as psalm does. Quite obvious.

https://psalm.dev/r/e3d927af68

[ondrejmirtes]

There's some extra code that makes sure this IS NOT reported: https://github.com/phpstan/phpstan-src/blob/4bfe42193d092be3bf004b03575ebeedbd957da6/src/Rules/Arrays/NonexistentOffsetInArrayDimFetchCheck.php#L49-L60

Even in Psalm it's an extra couple of options off by default: https://psalm.dev/docs/running_psalm/configuration/#ensurearraystringoffsetsexist

I'd accept a patch that adds an extra option for this behaviour.

[herndlm]

There are also more Info's about this at #7450 (reply in thread)

[desmax]

@ondrejmirtes may I ask why you chose not to report this?

[ondrejmirtes]

@desmax It'd report too many annoying things in existing codebases, like thousands of errors that aren't actually bugs...

[ptomulik]

@desmax It'd report too many annoying things in existing codebases, like thousands of errors that aren't actually bugs...

Well, most of things reported by static analysis tools are not actual bugs, but "just" potential bugs.

[herndlm]

It was mentioned that a PR that adds opt-in for this would be accepted. Shouldn't that be enough?

[ryazanov13]

It was mentioned that a PR that adds opt-in for this would be accepted. Shouldn't that be enough?

Hi, how soon can we expect the release of this feature?

[ondrejmirtes]

When someone implements it 😊

[ondrejmirtes]

Thanks to phpstan/phpstan-src#3028 in PHPStan 1.11 there will be two new options:

parameters:
    reportPossiblyNonexistentGeneralArrayOffset: true
    reportPossiblyNonexistentConstantArrayOffset: true

[ondrejmirtes]

Docs update 074f438

[ryazanov13]

Thanks to phpstan/phpstan-src#3028 in PHPStan 1.11 there will be two new options:

parameters:
    reportPossiblyNonexistentGeneralArrayOffset: true
    reportPossiblyNonexistentConstantArrayOffset: true

thank you very much!