[HttpKernel] Allow dynamic header values within the WithHttpStatus attribute

[angelov]

Q	A
Branch?	6.3
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	/
License	MIT
Doc PR	TODO

This extends the functionality provided with the #[HttpStatus] #[WithHttpStatus] attribute to be allowing the header values to be set dynamically.

With the current implementation, the header values must be hard-coded:

#[WithHttpStatus(
    statusCode: 422,
    headers: [
        'max-allowed-amount' => 500,
    ]
)]
class AmountTooBigException extends \Exception
{
    public function __construct(public readonly int $maxAllowedAmount)
    {
    }
}

With this, we can provide an Symfony\Component\ExpressionLanguage\Expression object as value for any of the headers, which will be evaluated when preparing the response.
Note that the exception object can be accessed in the expression by using this, as in the example bellow.

#[WithHttpStatus(
    statusCode: 422,
    headers: [
        'max-allowed-amount' => new Expression('this.maxAllowedAmount'),
        'hard-coded-value' => 'still-possible',
    ]
)]
class AmountTooBigException extends \Exception
{
    public function __construct(public readonly int $maxAllowedAmount)
    {
    }
}

Note that this requires the ExpressionLanguage so it is added as a suggested package.
To be honest, I am not really sure if this is useful enough to add a new optional dependency, but I wanted to hear more opinions.

[carsonbot]

Hey!

I think @HeahDude has recently worked with this code. Maybe they can help review this?

Cheers!

Carsonbot

[angelov]

The change requested by fabbot is not related:

-            KazInfoTehTransportFactory::class => 'notifier.transport_factory.kaz-info-teh',
+            KazInfoTehTransportFactory::class => 'notifier.transport_factory.kaz-info-the',

https://fabbot.io/patch/symfony/symfony/48890/71d5b22d86d0da2be2b1542bdd45207322a013fb/typos.diff

[nicolas-grekas]

The implementation LGTM but I don't really have an opinion whether we need this.
An alternative is to implement HttpExceptionInterface, at the cost of some coupling with HttpKernel.
Another approach could be to allow headers to be a string, which would then be used as the name of the method that returns the headers.

[nicolas-grekas]

Let me close this because we didn't get much traction here. Let's reconsider if one has a real world need.
Thanks for submitting!