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References: <a995ac24905030e168e7f6006b996cd5@bastelstu.be>
In-Reply-To: <a995ac24905030e168e7f6006b996cd5@bastelstu.be>
Date: Thu, 13 Feb 2025 11:21:22 +0100
Message-ID: <CANS-=pdhwB0mZmTga2H0fr3RbHr1Qw+Wm6xS1emww0-2aw7BiQ@mail.gmail.com>
Subject: Re: [PHP-DEV] RFC: Marking return values as important (#[\NoDiscard])
To: =?UTF-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>
Cc: Volker Dusch <volker@tideways-gmbh.com>, php internals <internals@lists.php.net>
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From: kjarli@gmail.com (Lynn)

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On Wed, Jan 29, 2025 at 4:14=E2=80=AFPM Tim D=C3=BCsterhus <tim@bastelstu.b=
e> wrote:

> Hi
>
> Volker and I would like to start discussion on our RFC to allow "Marking
> return values as important (#[\NoDiscard])".
>
> Please find the following resources for your reference:
>
> - RFC: https://wiki.php.net/rfc/marking_return_value_as_important
> - Implementation: https://github.com/php/php-src/pull/17599
>
> Best regards
> Tim D=C3=BCsterhus
>

I don't see this as something useful when you want to force interactions
with variables. I do see value in using this for the keeping and closing of
resources, but the only error you should ever get is when you use
`#[NoDiscard]` without a return value.

https://3v4l.org/L4bOc

<?php

#[NoDiscard]
function lockFile(string $path) {
    $handle =3D fopen($path, 'r+');
    if (! $handle || ! flock($handle, LOCK_EX)) {
        throw new RuntimeException('Failed locking ' . $path);
    }
    return $handle;
}

// what we write
function main() {
    lockFile($path);
    doSomething();
    echo 'hi';
}

// gets rewritten internally to something like
function main() {
    $hidden =3D lockFile($path);
    doSomething();
    echo 'hi';
    unset($hidden);
}

// if we do assign it, we omit it all
// what we write here would not get rewritten
function main() {
    $handle =3D lockFile($path);
    doSomething();
    echo 'hi';
}

// if we were to ever get a "using"-like
// what we write
function main() {
    using {
        lockFile($path);
        doSomething();
    }
    echo 'hi';
}

// gets rewritten internally to something like
function main() {
    $hidden =3D lockFile($path);
    doSomething();
    unset($hidden);
    echo 'hi';
}

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote g=
mail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, Jan 29,=
 2025 at 4:14=E2=80=AFPM Tim D=C3=BCsterhus &lt;<a href=3D"mailto:tim@baste=
lstu.be">tim@bastelstu.be</a>&gt; wrote:<br></div><blockquote class=3D"gmai=
l_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,20=
4,204);padding-left:1ex">Hi<br>
<br>
Volker and I would like to start discussion on our RFC to allow &quot;Marki=
ng <br>
return values as important (#[\NoDiscard])&quot;.<br>
<br>
Please find the following resources for your reference:<br>
<br>
- RFC: <a href=3D"https://wiki.php.net/rfc/marking_return_value_as_importan=
t" rel=3D"noreferrer" target=3D"_blank">https://wiki.php.net/rfc/marking_re=
turn_value_as_important</a><br>
- Implementation: <a href=3D"https://github.com/php/php-src/pull/17599" rel=
=3D"noreferrer" target=3D"_blank">https://github.com/php/php-src/pull/17599=
</a><br>
<br>
Best regards<br>
Tim D=C3=BCsterhus<br></blockquote><div><br></div><div>I don&#39;t see this=
 as something useful when you want to force interactions with variables. I =
do see value in using this for the keeping and closing of resources, but th=
e only error you should ever get is when you use `#[NoDiscard]` without a r=
eturn value.</div><div><br></div><div><a href=3D"https://3v4l.org/L4bOc">ht=
tps://3v4l.org/L4bOc</a></div><div><br></div><div>&lt;?php<br><br>#[NoDisca=
rd]<br>function lockFile(string $path) {<br>=C2=A0 =C2=A0 $handle =3D fopen=
($path, &#39;r+&#39;);<br>=C2=A0 =C2=A0 if (! $handle || ! flock($handle, L=
OCK_EX)) {<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 throw new RuntimeException(&#39;F=
ailed locking &#39; . $path);<br>=C2=A0 =C2=A0 }<br>=C2=A0 =C2=A0 return $h=
andle;<br>}<br><br>// what we write<br>function main() {<br>=C2=A0 =C2=A0 l=
ockFile($path);<br>=C2=A0 =C2=A0 doSomething();<br>=C2=A0 =C2=A0 echo &#39;=
hi&#39;;<br>}<br><br>// gets rewritten internally to something like<br>func=
tion main() {<br>=C2=A0 =C2=A0 $hidden =3D lockFile($path);<br>=C2=A0 =C2=
=A0 doSomething();<br>=C2=A0 =C2=A0 echo &#39;hi&#39;;<br>=C2=A0 =C2=A0 uns=
et($hidden);<br>}<br><br>// if we do assign it, we omit it all<br>// what w=
e write here would not get rewritten<br>function main() {<br>=C2=A0 =C2=A0 =
$handle =3D lockFile($path);<br>=C2=A0 =C2=A0 doSomething();<br>=C2=A0 =C2=
=A0 echo &#39;hi&#39;;<br>}<br><br>// if we were to ever get a &quot;using&=
quot;-like<br>// what we write<br>function main() {<br>=C2=A0 =C2=A0 using =
{<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 lockFile($path);<br>=C2=A0 =C2=A0 =C2=A0 =
=C2=A0 doSomething();<br>=C2=A0 =C2=A0 }<br>=C2=A0 =C2=A0 echo &#39;hi&#39;=
;<br>}<br><br>// gets rewritten internally to something like<br>function ma=
in() {<br>=C2=A0 =C2=A0 $hidden =3D lockFile($path);<br>=C2=A0 =C2=A0 doSom=
ething();<br>=C2=A0 =C2=A0 unset($hidden);<br>=C2=A0 =C2=A0 echo &#39;hi=
9;;<br>}</div></div></div>

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