Psalm acts differently depending on what version of PHP it is executed on.

[greg0ire]

Context: I'm trying to fix an error that does not happen in the CI of doctrine/orm, but does happen on my machine where I use PHP 7.4.

I tried fixing it with an assert, but now I get the opposite situation: doctrine/orm#8917

I cannot reproduce the issue on psalm.dev, that presumably does not run PHP 8

https://psalm.dev/r/a8f882ff61

On a machine with PHP 8, as well as on the CI, I know get this:

ERROR: RedundantConditionGivenDocblockType - lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php:912:13 - Docblock-defined type SimpleXMLElement for $action is never null (see https://psalm.dev/156)
            assert($action !== null);


ERROR: RedundantConditionGivenDocblockType - lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php:912:20 - Docblock-defined type SimpleXMLElement ca never contain null (see https://psalm.dev/156)
            assert($action !== null);

Either way, there is a difference in results depending on the version of PHP, and hardcoding phpVersion to 7.1 in psalm.xml does not help. I'm not sure what to try next.

See also: https://symfony-devs.slack.com/archives/C8SFXTD2M/p1628964600095200

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/a8f882ff61

<?php

function bar(SimpleXMLElement $a): void {
    foreach ($a->children() as $child) {
        assert($child !== null);
    }
}

Psalm output (using commit 4c26293):

No issues!

[weirdan]

Steps to reproduce:

gh repo clone doctrine/orm
cd orm/
gh pr checkout 8917
phpenv local 8.0.7
composer install
vendor/bin/psalm lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php
phpenv local system # 7.4.21
composer update -W
vendor/bin/psalm --clear-cache
vendor/bin/psalm lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php

[orklah]

Thanks for digging into this @greg0ire !

[weirdan]

Under 8.0, $action is inferred as SimpleXMLElement, while under 7.4 it's thought to be SimpleXMLIterator|null

[orklah]

It's unfortunate, we actually have a test case with a foreach loop over SimpleXmlElement::children, but it doesn't reproduce the issue...

[weirdan]

I think this may have to do with inheritance change in 8.0. In 8.0 SimpleXMLIterator::current() is inherited from SimpleXMLElement, and in 7.4 it's not.

[weirdan]

Yep. Stubbing SimpleXMLIterator as class SimpleXMLIterator extends SimpleXMLElement {} makes the error consistently appear for both 8.0 and 7.4.

Context: https://externals.io/message/108789 and php/php-src#5234

Still not sure what would be the best way to address this.

[greg0ire]

Shouldn't this be changed to SimpleXMLElement|null:

psalm/stubs/DOM.phpstub

Lines 96 to 97 in 4c26293

	/** @return SimpleXMLIterator */
	public function children(?string $namespaceOrPrefix = null, bool $isPrefix = false)

(like in the docs at https://www.php.net/manual/en/class.simplexmlelement.php?)