Add support for assertArrayHasKey and assertCount

[VincentLanglet]

This code is valid https://psalm.dev/r/e1d61bda01

But when I use assertArrayHasKey and assertCount, the offset are reported as possibly undefined.
It would be great to tell psalm that

assertArrayHasKey work as `array_key_exists` so the offset is not undefined for arrays
assertCount work as `count` so the offset is not undefined for list

I'm not familiar with, but I'm not sure it can be done with psalm assertion https://psalm.dev/docs/annotating_code/assertion_syntax/

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/e1d61bda01

<?php

/**
 * @return array<string, list<string>>
 */
function foo() {
    return [];
}

function foo2(): string
{
    $a = foo();
    assert(array_key_exists('foo', $a));
    
    $foo = $a['foo'];
    assert(count($foo) === 1);
    
    return $foo[0];
}

Psalm output (using commit 9222b24):

No issues!

[zerkms]

I'm 99% sure it's impossible to implement with just @psalm-assertion (via stubbing) and it would require writing a plugin.

[VincentLanglet]

@orklah maybe it's a good opportunity for some new features about @psalm-assertion wdyt ?

[orklah]

I think you should already be able to use non-empty-countable or the inverted !non-empty-countable as an assertion to reconcile a non empty array or an empty array (but technically, empty or !empty would probably be enough in most contexts, unless you also need to assert arrayness)

count() with greater or less than comparison would be harder without a plugin because the assertion is technically has-at-least-X (or !has-at-least-X) X being the number you compared against

Same with equal comparison, the assertion is has-exact-count-X (or !has-exact-count-X)

The harder will probably be key existence. Psalm has specific code for that because it implies to recursively change the type of different array dimensions. (Think assert(array_key_exists('a', $a['foo']['bar']));. Psalm must change the type of $a['foo']['bar'], $a['foo'] and $a.

You'd need to recheck but there are actually two set of assertions depending on what you want to change has-array-key-X and array-key-exists (the last one doesn't have X because it is applied directly onto the targeted variable id, like $a['a'])

If you want to progress on that, you'd have to find a syntax to use a param value to complete the assertion. (Something like @psalm-assert has-exact-count-$b $a for a function that takes $a as an array and $b as a count). You'd enter the realm of what you do when $b is not a single literal :)

This might be easier with a plugin, but I'm not actually sure on which hook you should code for adding assertions into Psalm though...

[orklah]

What I said above is partially true. I just learned that internal assertions are not available automatically to docblock assertions.

Given the changes to be made, it's only a small hiccup more, but it's important to note.

[VincentLanglet]

I again encounter issue with assertArrayHasKey.

Phpstan has somehthing like a TypeSpecifier https://github.com/phpstan/phpstan-phpunit/blob/15dc3e0d81b711c38d02fb33fe4482dfa570951c/src/Type/PHPUnit/Assert/AssertTypeSpecifyingExtensionHelper.php

Is there something equivalent in psalm ?

[orklah]

https://github.com/vimeo/psalm/blob/11e60fa261c682627e6b85300dd6f424b87520b1/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php#L926

This is the method that handles assert calls in the code.

You could use some variation of this in a plugin hooked to assertArrayHasKey and assertCount to have the same effect as if they were simple asserts I guess.

I hoped to find another entry point to our internal assertion module but I couldn't find one. It could be cool to be able to add an arbitrary assertion to a variable from plugins, especially with Psalm 5 that's coming with the brand new system :)

@muglug, maybe I missed something? How would you add an arbitrary assertion from a plugin?

[VincentLanglet]

https://github.com/vimeo/psalm/blob/11e60fa261c682627e6b85300dd6f424b87520b1/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php#L926

This is the method that handles assert calls in the code.

You could use some variation of this in a plugin hooked to assertArrayHasKey and assertCount to have the same effect as if they were simple asserts I guess.

I hoped to find another entry point to our internal assertion module but I couldn't find one. It could be cool to be able to add an arbitrary assertion to a variable from plugins, especially with Psalm 5 that's coming with the brand new system :)

@muglug, maybe I missed something? How would you add an arbitrary assertion from a plugin?

I would really like to add the assertArrayHasKey feature to this library, but I understand nothing to this code 🥲

[orklah]

I understand nothing to this code

I'm not sure it's even required that you do. I think you could just add this function somewhere in this plugin and call it.

Which means, all it would take is to send the correct value here: https://github.com/vimeo/psalm/blob/11e60fa261c682627e6b85300dd6f424b87520b1/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php#L929

Those are nodes from PHParser that need to be simulated (i.e. replacing the assertArrayHasKey($array, $key) by array_key_exists($array, $key)) and just roll with it

[VincentLanglet]

Those are nodes from PHParser that need to be simulated (i.e. replacing the assertArrayHasKey($array, $key) by array_key_exists($array, $key)) and just roll with it

Best would be to be able to support the syntax

/** 
 * @psalm-assert-if-true isset($array[$key])
 */

It would also be useful for webmozart/assert,
https://github.com/webmozarts/assert/blob/master/src/Assert.php#L1678
because there is no psalm/assert-plugin and this could just be solved with phpdoc.

[zerkms]

would be to be able to support the syntax

it would be horrible: it addresses one specific use case by creating a special unique syntax that you (as a user) now need to learn and maintain (as psalm developer). And that knowledge would not scale, eg: @psalm-assert-if-true myfunction($key) <- what would this mean?

[VincentLanglet]

would be to be able to support the syntax

it would be horrible: it addresses one specific use case by creating a special unique syntax that you (as a user) now need to learn and maintain (as psalm developer). And that knowledge would not scale, eg: @psalm-assert-if-true myfunction($key) <- what would this mean?

psalm supports

if (isset($array[$key])) {
     // Understand that the key exists
}

the syntax

/** 
 * @psalm-assert-if-true expression
 */

could be translated to

if (expression) {
}

so it would be a generic feature, and not a specific one.

In your example, @psalm-assert-if-true myfunction($key), will be resolved the same way it would be resolved by psalm if you wrote

if (myfunction($key)) {
}

[zerkms]

will be resolved the same way

what would it mean type-wise? What assertion would it establish?