Future compatibility with function autoloading

[withinboredom]

Q	A
Branch?	7.2
Bug fix?	yes?
New feature?	no
Deprecations?	no
Issues	php/php-src#15471
License	MIT

While working on an RFC (https://wiki.php.net/rfc/function_autoloading4) for function autoloading, I discovered that Symfony registers an autoloader that accepts two arguments. But an autoloader should never accept a second argument for the current implementation, and the implementation may change.

[carsonbot]

Hey!

I see that this is your first PR. That is great! Welcome!

Symfony has a contribution guide which I suggest you to read.

In short:

• Always add tests
• Keep backward compatibility (see https://symfony.com/bc).
• Bug fixes must be submitted against the lowest maintained branch where they apply (see https://symfony.com/releases)
• Features and deprecations must be submitted against the 7.2 branch.

Review the GitHub status checks of your pull request and try to solve the reported issues. If some tests are failing, try to see if they are failing because of this change.

When two Symfony core team members approve this change, it will be merged and you will become an official Symfony contributor!
If this PR is merged in a lower version branch, it will be merged up to all maintained branches within a few days.

I am going to sit back now and wait for the reviews.

Cheers!

Carsonbot

[fabpot]

Is it something we want to do in 5.4 instead?

[nicolas-grekas]

This likely breaks stack trace inspection latter in the method. I'd suggest waiting for the linked RFC to be accepted before merging. The current usage is fine for the moment.

[nicolas-grekas]

Suggested change

	$thrower = fn(string $name) => self::throwOnRequiredClass($name);
	$thrower = static fn ($class) => self::throwOnRequiredClass($class);

[nicolas-grekas]

Let me close for now.

[derrabus]

But an autoloader should never accept a second argument for the current implementation, and the implementation may change.

Given that we can currently be certain that PHP won't pass a second argument to the autoloader, I don't see a problem to register a method as autoloader that takes an optional second argument.

The change proposed in the RFC breaks backwards compatibility. That should be taken into consideration when discussing and refining the RFC.