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Date: Thu, 16 Apr 2020 08:46:33 +0200
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To: Larry Garfield <larry@garfieldtech.com>
Cc: php internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="000000000000c7716705a362cbd5"
Subject: Re: [PHP-DEV] Re: [RFC] Attributes v2
From: kontakt@beberlei.de (Benjamin Eberlei)

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On Tue, Apr 14, 2020 at 6:14 PM Larry Garfield <larry@garfieldtech.com>
wrote:

> On Tue, Apr 14, 2020, at 10:42 AM, Benjamin Eberlei wrote:
> > On Tue, Apr 14, 2020 at 5:24 PM Larry Garfield <larry@garfieldtech.com>
> > wrote:
>
> > > 2. Regarding sub-annotations, can you still do classes as parameters
> even
> > > if not as an annotation marker?  Eg:
> > >
> > > <<Foo(1, "B", Bar('blah'))>>
> > > function foo()
> > >
> > > Or is that also a no-go?
> > >
> >
> > This is a no go because it would require reimplementing constant ASTs,
> > which is as of now 300 lines of tricky code evaluating ASTs and allowing
> > this would also clash with Bar("Blah") reading like a function call,
> which
> > is confusing and would prevent reconciliation with constant ASTs in the
> > future.
>
> Sad panda.
>
> > > 3. I see the most common case for attributes being getting the object
> > > version.  With the reflection API as currently described, I see two
> > > shortcomings.
> > >
> > > A) I can't tell if an attribute has a valid object or not before
> trying to
> > > access it, which would presumably fail spectacularly.  I believe we
> need a
> > > way to know if getObject() is going to return a valid value before
> trying
> > > to call it.  I think this is a hard-requirement.
> > >
> > > B) Related, as is getting all attributes as objects looks to be rather
> > > clunky.
> > >
> > > $attribute_objectgs =
> array_filter(array_map(function(ReflectionAttribute
> > > $r) {
> > >   if ($r->getObject()) { // Needs something better here.
> > >     return $r->getObject();
> > >   }
> > > }, $obj->getAttributes()));
> > >
> > > That's gross. :-)  Can "get all the attributes that can be formed into
> > > objects" be its own operation?  $obj->getAttributeObjects() or some
> such,
> > > that skips over non-instantiable attributes and instantiates the rest?
> > >
> >
> > I don't see A.) what would you do when the object instantiation fails?
> You
> > would throw an exception I presume, let the engine throw the regular
> > TypeError, ArgumentError, Error if class not exists that everyone is
> > already familiar with.
> >
> > For B.) I believe you are extrapolating based on your own use case.
> Working
> > with Reflection is usually a lot of boilerplate, I don't believe we need
> to
> > have a one liner here.
>
> It depends on the annotation, I suppose.  If I'm requesting a specific
> annotation by name, presumably I know if it is supposed to have an
> associated class.  If it's supposed to but it's missing, that's a legit
> class-not-found exception/error.
>
> However, I'm thinking of cases where code is integrating with a 3rd party
> optionally, through an annotation.  In that case it's a fair question of
> whether the class will be defined or not based on whether some other
> library is present.
>
> Similarly, if a bit of code is requesting all attributes (as above) rather
> than just specific ones by name, it wouldn't know if a given attribute is
> supposed to be defined or not; as written, class-less attributes are
> supported.
>
> I suppose the workaround would be class_exists($r->getName()).  Weird but
> I guess works?  It would have to be documented as a thing you should do,
> though, which implies to me that it could be made cleaner.
>
> That reflection is usually clunky today (true) is to me not a compelling
> argument that it shouldn't be made less clunky. :-)
>

You are not safe from these problems when using Doctrine Annotations either
(missing library or class does not exist) and it fails exactly the same way
as trying to instantiate something that doesn't exist.

I also realized why IS_INSTANCEOF is not the default, because it needs to
resolve all attributes to classes to perform the check. This triggers
autoloading *all* attributes of the reflected declaration (even the ones
not requested), so we felt it should not be the default.


> --Larry Garfield
>
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