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Date: Thu, 21 Apr 2016 21:05:56 -0400
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To: Dmitry Stogov <dmitry@zend.com>
Cc: Dominic Grostate <codekestrel@googlemail.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] PHP Attributes
From: guilhermeblanco@gmail.com ("guilhermeblanco@gmail.com")

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Hi Dmitry,

As a previous suggester of metadata information built-in into PHP, and also
one of developers of the most used metadata library written in PHP, I
understand this feature implementation requires several design decisions
and also a good understanding of specific situations users may require.

While I am a strong supporter of a more robust solution, this is already a
good start.
A few things I'd like to ask for my own understanding and also suggestions
too:

1- I understand you took a minimalistic approach towards a "dumb"
implementation for attributes (when I mean "dumb", the idea here is towards
a non-OO approach). Can you explain your motivations towards this approach?

I see two distinct approaches of implementation for this feature. Both of
them have some common demands, like lazy initialization of metadata. Here
they are:

- Simplistic approach, which lets consumers of the feature do all the work
related to validation, assertion of valid keys, values, etc
This does not invalidate the ability to leverage of some features that a
more robust implementation demands.

- Robust approach: language takes the burden of instantiating complex
structures, validating, assertion of valid keys, values, if this complex
structure is allowed to be instantiated in that given class, method, etc.

1- Your approach is basically defining an array. Could you explain your
line of thinking on why you didn't consider a syntax like the one below?

<["key" => "value"]>
class Foo {}

2- I see that you added support over functions, classes, constants and
properties. According to the RFC, getAttributes() was added over
ReflectionFunction. Is there a reason why support was not added to methods
(ReflectionMethod extends ReflectionFunctionAbstract, which was not
mentioned on RFC)? Any reason to not support it in function/method
parameters?

3- Did you put any thought on inheritance? What I mentioned in comment #1
is even smaller than what you implemented in RFC.
Assuming you keep the RFC approach, did you consider support overrides,
inherit, etc?

4- I understand that a more robust attribute solution would be required to
achieve this, but one of the biggest advantages of AOP is the ability to
perform custom logic before, after or around... However, I don't know if
any kind of triggers came in your head or are planned as a future RFC.
Let me highlight one example: Every time a class, property or method is
called that is annotated as <<deprecated>>, I would like to issue an
E_USER_DEPRECATED warning. A trigger-like solution would be required. Did
this concept came to your mind?



Regards,

On Thu, Apr 21, 2016 at 7:44 PM, Dmitry Stogov <dmitry@zend.com> wrote:

>
>
> On 04/22/2016 02:16 AM, Dominic Grostate wrote:
>
>>
>> This is amazing.  It would actually allow us to implement our automated
>> assertions ourselves, as opposed to requiring it within the language.
>>
>> this was the idea - to give a good tool instead of implementing every
> possible use-case in the language.
>
> Could it also support references?
>>
>> <<sanitize(&$a)>>
>> function foo($a) {
>>
>> }
>>
>> yes. "&$a" is a valid PHP expression.
>
> If you plan to use this, I would appreciate, if you to build the patched
> PHP and try it.
> The early we find problems the better feature we will get at the end.
>
> Thanks. Dmitry.
>
>
> On 21 Apr 2016 10:13 p.m., "Dmitry Stogov" <dmitry@zend.com <mailto:
>> dmitry@zend.com>> wrote:
>>
>>     Hi,
>>
>>
>>     I would like to present an RFC proposing support for native
>>     annotation.
>>
>>     The naming, syntax and behavior are mostly influenced by HHVM
>>     Hack, but not exactly the same.
>>
>>     The most interesting difference is an ability to use arbitrary PHP
>>     expressions as attribute values.
>>
>>     These expressions are not evaluated, but stored as Abstract Syntax
>>     Trees, and later may be accessed (node by node) in PHP extensions,
>>     preprocessors and PHP scripts their selves. I think this ability
>>     may be useful for "Design By Contract", other formal verification
>>     systems, Aspect Oriented Programming, etc
>>
>>
>>     https://wiki.php.net/rfc/attributes
>>
>>
>>     Note that this approach is going to be native, in contrast to
>>     doc-comment approach that uses not well defined syntax, and even
>>     not parsed by PHP itself.
>>
>>
>>     Additional ideas, endorsement and criticism are welcome.
>>
>>
>>     Thanks. Dmitry.
>>
>>
>


-- 
Guilherme Blanco
Lead Architect at E-Block

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