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Date: Mon, 14 Oct 2024 05:37:50 +0300
Message-ID: <CAPyeZ4O0Dc9ggrhCLBsnihqQcuBTr9EMSAXFBf6N+vwAy49uiw@mail.gmail.com>
Subject: Re: [PHP-DEV] Asymmetric visibility is a BC break
To: Jordan LeDoux <jordan.ledoux@gmail.com>
Cc: Rob Landers <rob@bottled.codes>, internals@lists.php.net
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From: udaltsov.valentin@gmail.com (Valentin Udaltsov)

On Mon, 14/10/2024=E2=80=AF05:01, Jordan LeDoux <jordan.ledoux@gmail.com>:
>
>
>
> On Sun, Oct 13, 2024 at 5:03=E2=80=AFPM Valentin Udaltsov <udaltsov.valen=
tin@gmail.com> wrote:
>>
>> On Mon, 14 Oct 2024=E2=80=AFat 01:28, Jordan LeDoux <jordan.ledoux@gmail=
.com>:
>> > Backwards compatible has never, in any work I've done through my entir=
e career, meant something like "if you take old code and then update it to =
the new version incorrectly, it doesn't work"... that seems... obvious?
>> >
>> > What exactly is the claim being made here? Because it sounds like the =
claim is very much that second "definition".
>> >
>> > Jordan
>>
>> Hi, Jordan!
>>
>> The problem is that in practice most of the PHP libraries consider
>> themselves to be compatible with newer PHP versions.
>>
>> For instance, Symfony PropertyInfo uses `"php": ">=3D8.2"` constraint in
>> its `composer.json`. However, it is not compatible with PHP 8.4, I've
>> just created an issue: https://github.com/symfony/symfony/issues/58556
>>
>> The end user will be the victim, because `composer require
>> symfony/property-info` will happily install property-info v7.1.4 for
>> PHP 8.4, but it's not gonna work.
>>
>> --
>> Valentin
>
>
> How does a library that uses code that will not even compile (like `reado=
nly` or `private(set)`), but claims to not require a PHP version that uses =
the syntax, suddenly make a BC problem for the language? Composer allows li=
braries to set minimum PHP versions for releases. Any time you update your =
libraries, you may have to update your code which uses it. That's just part=
 of how libraries work.
>
> Jordan

First of all, I have already agreed above that PHP does not have a BC
break here. Now we are discussing the potential problems in the PHP
ecosystem and how they could be mitigated.

> Composer allows libraries to set minimum PHP versions for releases.

I think you've got the problem wrong. The problem is about the maximum
version, not the minimum one.

Consider the Symfony issue I've just reported:
https://github.com/symfony/symfony/issues/58556

Symfony PropertyInfo requires `php >=3D 8.2`. And it is written in PHP
8.2 syntax. So it can be safely installed and used in PHP 8.2 and 8.3.
In other words it's forward compatible. However, the `php >=3D 8.2`
constraint also allows installing it in PHP 8.4. And as it turned out,
PropertyInfo is not ready for 8.4 syntax (see my reproducer
https://github.com/vudaltsov/symfony-property-access-php84). In my
opinion, this is a problem, because a PHP 8.4 user can install the
library without any obstacles and only later find out that `private
(set)` properties do not work as expected there. Ideally
`symfony/property-info` should not be installable until it ensures to
be compatible with all the PHP 8.4 features. So, its PHP constraint
should be `>=3D8.2 && <8.4`. And then `>=3D8.2 && <8.5`, once the tests
pass for PHP 8.4 features.

--
Best regards,
Valentin