ChoiceType fails when there is `null` in array submitted

[nikola-jovanovic-php]

Symfony version(s) affected

7.0

Description

Warning: array_flip(): Can only flip string and integer values, entry skipped

How to reproduce

pass null value as an value of ChoiceType that has multiple option set to true (array of values).

{
    "choice": [null, ...]
}

Possible Solution

filter null values from array or convert them to empty string

Additional Context

failing line: https://github.com/symfony/form/blob/7.0/Extension/Core/Type/ChoiceType.php#L125

[xabbuh]

I fail to see how null can be part of the values submitted by a browser. Can you create a small example application that allows to reproduce the behaviour that you observe?

[nikola-jovanovic-php]

I fail to see how null can be part of the values submitted by a browser. Can you create a small example application that allows to reproduce the behaviour that you observe?

it's submitted by API via JSON body:

$builder = $this->createFormBuilder();
$builder->add('choices', ChoiceType::class, [
    'choices' => ['a' => 1, 'b' => 2, 'c' => 3],
    'multiple' => true
]);
$form = $builder->getForm();
$form->submit(['choices' => [null, 1]]);

No matter how that input have had happened, it's not expected behavior for error to occur. it should have been probably converted to empty string and then ChoiceType would proceed as usual.

[xabbuh]

The Form component is designed to work with HTML forms where the submitted data always is a string or arrays of strings. If you use it for your API where types can differ, you have to take care of registering custom transformers yourself that take care of additional types. That said I am going to close here as the observed behaviour is not a bug in the component. Thank you for understanding.