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Subject: [PHP-DEV] [RFC] [Discussion] Optional interfaces
Date: Sat, 28 Dec 2024 22:56:01 +0200
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From: juris@glaive.pro ("Juris Evertovskis")

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Hi,

 

I would like to propose a new syntax that let's 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're writing code that should work with
various versions of other libraries or PHP itself and when 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 of
those libraries would also benefit as this syntax would clearly communicate
the intention of optional interoperability. IDEs and static analysis tools
could also have easier time with `?OptionalInterface` instead of class
definitions inside an `if (interface_exists(.)) { . } else {.}`.

 

I've not entirely sure about the naming as an "optional interface" feels
like an oxymoron. I've also considered names like non-required interfaces,
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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link=3D"#467886" vlink=3D"#96607D" style=3D'word-wrap:break-word'><div =
class=3DWordSection1><p class=3DMsoNormal>Hi,<o:p></o:p></p><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p><p class=3DMsoNormal>I would like =
to propose a new syntax that let&#8217;s you implement an interface only =
if it exists.<o:p></o:p></p><p class=3DMsoNormal><o:p>&nbsp;</o:p></p><p =
class=3DMsoNormal>`class MyClass extends ?OptionalInterface =
{}`<o:p></o:p></p><p class=3DMsoNormal><o:p>&nbsp;</o:p></p><p =
class=3DMsoNormal>If the `OptionalInterface` exists, the class =
implements it. If no such interface can be found, it is =
ignored.<o:p></o:p></p><p class=3DMsoNormal><o:p>&nbsp;</o:p></p><p =
class=3DMsoNormal><a =
href=3D"https://wiki.php.net/rfc/optional-interfaces">https://wiki.php.ne=
t/rfc/optional-interfaces</a> <o:p></o:p></p><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p><p class=3DMsoNormal>The need to =
declare compatibility with a certain interface without requiring the =
interface itself comes up when you&#8217;re writing code that should =
work with various versions of other libraries or PHP itself and when a =
library provides interoperability with some other library or a PHP =
extension, but does not require it.<o:p></o:p></p><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p><p class=3DMsoNormal>Although =
this would mainly be used by library developers, the consumers of those =
libraries would also benefit as this syntax would clearly communicate =
the intention of optional interoperability. IDEs and static analysis =
tools could also have easier time with `?OptionalInterface` instead of =
class definitions inside an `if (interface_exists(&#8230;)) { &#8230; } =
else {&#8230;}`.<o:p></o:p></p><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p><p class=3DMsoNormal>I&#8217;ve =
not entirely sure about the naming as an &#8220;optional =
interface&#8221; feels like an oxymoron. I&#8217;ve also considered =
names like non-required interfaces, conditional interfaces, =
optional/conditional implementation or even soft interfaces/soft =
implementation. Please let me know if the naming itself bothers =
you.<o:p></o:p></p><p class=3DMsoNormal><o:p>&nbsp;</o:p></p><p =
class=3DMsoNormal>Previous discussion: <a =
href=3D"https://externals.io/message/125967">https://externals.io/message=
/125967</a><o:p></o:p></p><p class=3DMsoNormal>WIP implementation: <a =
href=3D"https://github.com/php/php-src/pull/17288">https://github.com/php=
/php-src/pull/17288</a><o:p></o:p></p><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p><p class=3DMsoNormal>Looking =
forward to your feedback and suggestions!<o:p></o:p></p><p =
class=3DMsoNormal>Juris<o:p></o:p></p></div></body></html>
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