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Date: Wed, 16 Mar 2022 09:57:04 +0100
References: <62317B01.90907@adviesenzo.nl>
To: PHP internals <internals@lists.php.net>
In-Reply-To: <62317B01.90907@adviesenzo.nl>
Message-ID: <3F016525-CCDE-4229-9260-7C76A6FF42E1@cschneid.com>
Subject: Re: [PHP-DEV] Deprecated partially supported callables: should
 is_callable() throw a deprecation notice ?
From: cschneid@cschneid.com (Christian Schneider)

Am 16.03.2022 um 06:52 schrieb Juliette Reinders Folmer =
<php-internals_nospam@adviesenzo.nl>:
> I've just been looking in detail at the Partially Supported Callables =
deprecation RFC: =
https://wiki.php.net/rfc/deprecate_partially_supported_callables
>=20
> The RFC explicitly excludes the `is_callable()` function and the =
`callable` type from throwing deprecation notices.
>=20
>> The |is_callable()| function and |callable| type remain side-effect =
free and do not throw a deprecation warning. They will continue to =
accept these callables until support is removed entirely.=20
>=20
> While I can fully support this for the `callable` type, I wonder if =
the decision to not throw a deprecation on use in `is_callable()` is the =
right one (though I understand the desire to keep it side-effect free).
>=20
> Consider these code samples:
>=20
>  function foo(callable $callback) {}
>  foo('static::method');
>=20
> This function call not throwing a deprecation is not problematic as in =
PHP 9.0 the function will start throwing a TypeError.

My reaction to your last sentence is actually quite the opposite: This =
is a major problem because code which was "just working" directly goes =
to a TypeError without a migration phase warning about it. This is =
something I've repeatedly advocated against.

>  if (is_callable('static::method')) {
>      static::method();
>  }
>=20
> The second code sample, however, is problematic, as in PHP 9.0, the =
behaviour of this code will be silently reversed for those callbacks =
which would previously result in `is_callable()` returning true, which =
makes this a potentially dangerous change without deprecation notice.

I agree with you here: Code which silently changes behavior is also a =
migration hassle.

- Chris