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Date: Fri, 14 Mar 2025 15:04:21 +0100
Message-ID: <CAPTD5yE0aDgLuoB6fCQawrz9syWfGqFfq6_8taPCEUB5252oeQ@mail.gmail.com>
Subject: Re: [PHP-DEV] [RFC] [Discussion] Optional interfaces
To: Juris Evertovskis <juris@glaive.pro>
Cc: php internals <internals@lists.php.net>
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From: jorg.sowa@gmail.com (Jorg Sowa)

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Hello Juris,
There is some uncertainty for me on how this approach would work with
namespaces.

Let's get this example:
https://3v4l.org/bI1Rj

I would expect to get the error message that I forgot to insert `use
Stringable;`.
But with your idea everything is fine. I don't like such ambiguity and I
worry it may bring some confusion to developers.

Kind regards,
Jorg

On Sat, Dec 28, 2024 at 9:57=E2=80=AFPM Juris Evertovskis <juris@glaive.pro=
> wrote:

> Hi,
>
>
>
> I would like to propose a new syntax that let=E2=80=99s you implement an =
interface
> only if it exists.
>
>
>
> `class MyClass extends ?OptionalInterface {}`
>
>
>
> If the `OptionalInterface` exists, the class implements it. If no such
> interface can be found, it is ignored.
>
>
>
> https://wiki.php.net/rfc/optional-interfaces
>
>
>
> The need to declare compatibility with a certain interface without
> requiring the interface itself comes up when you=E2=80=99re writing code =
that
> should work with various versions of other libraries or PHP itself and wh=
en
> a library provides interoperability with some other library or a PHP
> extension, but does not require it.
>
>
>
> Although this would mainly be used by library developers, the consumers o=
f
> those libraries would also benefit as this syntax would clearly communica=
te
> the intention of optional interoperability. IDEs and static analysis tool=
s
> could also have easier time with `?OptionalInterface` instead of class
> definitions inside an `if (interface_exists(=E2=80=A6)) { =E2=80=A6 } els=
e {=E2=80=A6}`.
>
>
>
> I=E2=80=99ve not entirely sure about the naming as an =E2=80=9Coptional i=
nterface=E2=80=9D feels
> like an oxymoron. I=E2=80=99ve also considered names like non-required in=
terfaces,
> conditional interfaces, optional/conditional implementation or even soft
> interfaces/soft implementation. Please let me know if the naming itself
> bothers you.
>
>
>
> Previous discussion: https://externals.io/message/125967
>
> WIP implementation: https://github.com/php/php-src/pull/17288
>
>
>
> Looking forward to your feedback and suggestions!
>
> Juris
>

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<div dir=3D"ltr"><div><div><div><div><div>Hello Juris,<br></div>There is so=
me uncertainty for me on how this approach would work with namespaces.<br><=
br></div>Let&#39;s get this example:<br><a href=3D"https://3v4l.org/bI1Rj">=
https://3v4l.org/bI1Rj</a><br><br></div>I would expect to get the error mes=
sage that I forgot to insert `use Stringable;`. <br>But with your idea ever=
ything is fine. I don&#39;t like such ambiguity and I worry it may bring so=
me confusion to developers.<br><br></div>Kind regards,<br></div>Jorg</div><=
br><div class=3D"gmail_quote gmail_quote_container"><div dir=3D"ltr" class=
=3D"gmail_attr">On Sat, Dec 28, 2024 at 9:57=E2=80=AFPM Juris Evertovskis &=
lt;<a href=3D"mailto:juris@glaive.pro">juris@glaive.pro</a>&gt; wrote:<br><=
/div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;bo=
rder-left:1px solid rgb(204,204,204);padding-left:1ex"><div class=3D"msg-17=
46763104004614392"><div lang=3D"LV" style=3D"overflow-wrap: break-word;"><d=
iv class=3D"m_-1746763104004614392WordSection1"><p class=3D"MsoNormal">Hi,<=
u></u><u></u></p><p class=3D"MsoNormal"><u></u>=C2=A0<u></u></p><p class=3D=
"MsoNormal">I would like to propose a new syntax that let=E2=80=99s you imp=
lement an interface only if it exists.<u></u><u></u></p><p class=3D"MsoNorm=
al"><u></u>=C2=A0<u></u></p><p class=3D"MsoNormal">`class MyClass extends ?=
OptionalInterface {}`<u></u><u></u></p><p class=3D"MsoNormal"><u></u>=C2=A0=
<u></u></p><p class=3D"MsoNormal">If the `OptionalInterface` exists, the cl=
ass implements it. If no such interface can be found, it is ignored.<u></u>=
<u></u></p><p class=3D"MsoNormal"><u></u>=C2=A0<u></u></p><p class=3D"MsoNo=
rmal"><a href=3D"https://wiki.php.net/rfc/optional-interfaces" target=3D"_b=
lank">https://wiki.php.net/rfc/optional-interfaces</a> <u></u><u></u></p><p=
 class=3D"MsoNormal"><u></u>=C2=A0<u></u></p><p class=3D"MsoNormal">The nee=
d to declare compatibility with a certain interface without requiring the i=
nterface itself comes up when you=E2=80=99re writing code that should work =
with various versions of other libraries or PHP itself and when a library p=
rovides interoperability with some other library or a PHP extension, but do=
es not require it.<u></u><u></u></p><p class=3D"MsoNormal"><u></u>=C2=A0<u>=
</u></p><p class=3D"MsoNormal">Although this would mainly be used by librar=
y developers, the consumers of those libraries would also benefit as this s=
yntax would clearly communicate the intention of optional interoperability.=
 IDEs and static analysis tools could also have easier time with `?Optional=
Interface` instead of class definitions inside an `if (interface_exists(=E2=
=80=A6)) { =E2=80=A6 } else {=E2=80=A6}`.<u></u><u></u></p><p class=3D"MsoN=
ormal"><u></u>=C2=A0<u></u></p><p class=3D"MsoNormal">I=E2=80=99ve not enti=
rely sure about the naming as an =E2=80=9Coptional interface=E2=80=9D feels=
 like an oxymoron. I=E2=80=99ve also considered names like non-required int=
erfaces, conditional interfaces, optional/conditional implementation or eve=
n soft interfaces/soft implementation. Please let me know if the naming its=
elf bothers you.<u></u><u></u></p><p class=3D"MsoNormal"><u></u>=C2=A0<u></=
u></p><p class=3D"MsoNormal">Previous discussion: <a href=3D"https://extern=
als.io/message/125967" target=3D"_blank">https://externals.io/message/12596=
7</a><u></u><u></u></p><p class=3D"MsoNormal">WIP implementation: <a href=
=3D"https://github.com/php/php-src/pull/17288" target=3D"_blank">https://gi=
thub.com/php/php-src/pull/17288</a><u></u><u></u></p><p class=3D"MsoNormal"=
><u></u>=C2=A0<u></u></p><p class=3D"MsoNormal">Looking forward to your fee=
dback and suggestions!<u></u><u></u></p><p class=3D"MsoNormal">Juris<u></u>=
<u></u></p></div></div></div></blockquote></div>

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