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Date: Mon, 28 Sep 2020 19:06:24 +0200
Message-ID: <CAEPJdu=dZPQbeCktySON=yVCpMgURqu7xkEM_PEZVDt=oqVVZQ@mail.gmail.com>
To: Benjamin Morel <benjamin.morel@gmail.com>
Cc: Nicolas Grekas <nicolas.grekas+php@gmail.com>, Nikita Popov <nikita.ppv@gmail.com>, 
	PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Re: Attributes and constructor property promotion
From: kontakt@beberlei.de (Benjamin Eberlei)

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On Mon, Sep 28, 2020 at 4:35 PM Benjamin Morel <benjamin.morel@gmail.com>
wrote:

> On Mon, 28 Sep 2020 at 15:17, Nicolas Grekas <nicolas.grekas+php@gmail.co=
m>
> wrote:
>
>> I assume the 80% case is properties, because attributes did not have
>>> docblock annotations yet, that means this use-case isn't even possible =
at
>>> the moment. Yet annotations on properties are widespread (Doctrine ORM,
>>> symfony validator, ...).
>>>
>>
>> I'm 100% with Benjamin here, this is what will be the most useful to me
>> also.
>>
>
> To be clear, I don't have a strong opinion against yours, I'm just
> pointing out the fact that even though it might be useful, it might also =
be
> confusing and create yet another WTF moment in PHP for developers. Sure, =
it
> might make more sense to apply to the property. Sure, so far annotations
> weren't possible on parameters. But is that obvious to the average
> developer writing the attribute? A few years down the road, DI containers
> may have broad support for annotating parameters for injection. Will it
> still be obvious then that an attribute on a promoted property applies to
> the property only?
>
> I do agree that applying the attribute to both the property and the
> parameter will probably never be useful, though. So, throwing an exceptio=
n
> and forcing the de-sugaring feels like the most sensible thing to do for =
me
> in this case!
>

I haven't checked if this is possible in the code doing the "desugering",
but what if we had an attribute on the constructor that could specify where
the attributes should apply to?

#[AttributePromotion(Attribute::TARGET_PROPERTY)]
public function __construct(#[Foo] public string $bar) {}

Then we could apply it to both by default, which is what is probably the
expected approach, and users could change it to apply only to properties,
which is what is the use-case that makes most sense.

>
> =E2=80=94 Benjamin
>

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