use readonly in args of constructor, in components/

[alexislefebvre]

This is a follow-up of #18049

I only updated some constructors from the components/ directory, to ensure that maintainers agree before modifying all the files.

Some files have been omitted because it looks like they must be initialized more than once:

symfony-docs/components/event_dispatcher.rst

Line 300 in 9f8ca28

protected Order $order,

symfony-docs/components/lock.rst

Lines 91 to 92 in 9f8ca28

	private object $article,
	private Key $key,

And this example is about reading annotations, so I think it must be kept as is:

symfony-docs/components/property_info.rst

Line 438 in 9f8ca28

private $bar,

[OskarStark]

CPP was introduced in PHP 8.0, which is what Symfony 6.2 needs as minimum requirement.
readonly properties were introduced in PHP 8.1.

So I would be strict to not merge readonly to the docs, unless we require at least Symfony 8.1 for a version.

@symfony/team-symfony-docs do you agree?

@alamirault @MrYamous we should add a rule to DOCtor then to ensure this 👍

[OskarStark]

Oh I was wrong, in the first step we required PHP 8.0, but then switched to 8.1. My fault.

Another aspect is, that CPP reduced the lines of code, while readonly brings nearly no benefit while reading the docs.

I would vote 👎 on this topic

[alexislefebvre]

I see php: >=8.1 here: https://packagist.org/packages/symfony/symfony#v6.2.7

It comes from here: https://github.com/symfony/symfony/blob/v6.2.7/composer.json#L36

Do some components require php: >=8.0?

/dependency-injection requires php: >=8.1 too: https://packagist.org/packages/symfony/dependency-injection#v6.2.7

[alexislefebvre]

Oh I was wrong, in the first step we required PHP 8.0, but then switched to 8.1. My fault.

Another aspect is, that CPP reduced the lines of code, while readonly brings nearly no benefit while reading the docs.

I would vote -1 on this topic

Thanks for your input, this is interesting.

readonly prevent making a mistake like:

        public function __construct(
            private readonly LoggerInterface $logger,
        ) {
        }

        public function doSomething() {
            $this->logger = 'a'; // this is not valid
        }

We can consider that it's an edge case to write this typo and keep the examples as is.

What other people think about this?

[MrYamous]

In context of documentation I feel like using readonly does not add much value but can lead to additionnal maintenance effort as even if it is mostly appropriate to use it (from code pov), sometimes not, and we will have to be careful about that to not have invalid examples