Validation NotBlank on a non nullable field - php

Question

I'm trying to validate a form that includes a field that absolutely cannot be empty or null. So in my model, it is defined like this:
/**
* #var string
*/
private $end;
/**
* #param string $end
* #return Blabla
*/
public function setEnd(string $end): Blabla
{
$this->end = $end;
return $this;
}
Here is the validation of this field in my form:
$builder
->add('end', TextType::class, [
'label' => 'blabla',
'constraints' => [
new Length([
'min' => 3,
'minMessage' => 'Min {{ limit }} chars',
]),
new NotBlank([
'message' => 'not null blabla',
]),
],
])
Here is the error I receive when I send a wrong input per example "multiple spaces" :
Expected argument of type "string", "null" given at property path "end".
I can correct this error by adding the possibility to receive a null in my setter
/**
* #var string|null
*/
private $end;
/**
* #param string|null $end
* #return blabla
*/
public function setEnd(?string $end=null): blabla
{
$this->end = $end;
return $this;
}
But I don't find it very coherent to allow a field to receive null only to validate it and prevent to set the field with null value.
Can't we do otherwise?

Answer 1

When form is submitted, all empty values are set to null by default so you should either accept null in your setter or use empty_data to customise default value:
The model:
#[Assert\NotBlank]
private string $end = ''; // Remember to initialise the field with empty string if you use typed properties
public function setEnd(string $end): void
{
$this->end = $end;
}
Form:
$builder->add('end', TextType::class, [
'label' => 'blabla',
'empty_data' => '',
]);
Since NotBlank checks for empty string, you can still use it this way.
This works for some built-in fields like TextType but may still convert an empty string to null in other fields because DataTransformers are applied to empty_data too: docs
Form data transformers will still be applied to the empty_data value. This means that an empty string will be cast to null. Use a custom data transformer if you explicitly want to return the empty string.
If you want to costomize null handling in your form types, add a custom DataTransformer or implement DataTransformerInterface directly in your form type just like it's done in TextType: https://github.com/symfony/symfony/blob/5.4/src/Symfony/Component/Form/Extension/Core/Type/TextType.php
Please note that I used some of modern PHP features (Attributes and typed properties) to make the code a bit shorter.