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Date: Tue, 28 Jun 2016 18:03:05 +0100
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Subject: Re: [PHP-DEV] [RFC] Simple Annotations
From: rowan.collins@gmail.com (Rowan Collins)

Hi Rasmus,

I think you may be onto something here... :)


On 28/06/2016 17:31, Rasmus Schultz wrote:
> The UnknownAnnotation object has three properties: class-name,
> method-name ("__construct" if constructor was used) and the list of
> arguments.

I'm not sure we need an extra UnknownAnnotation class. It seems like all 
of that information could be available on the ReflectionAnnotation 
object, so you can get it without the class being available if you want to.

If the idea is to lazily-evaluate the arguments to the annotation, that 
could be handled by storing the AST and only evaluating them when you 
call either $annotation->getInstance() or $annotation->getArguments():

use MyAnnotations\FooAnnotation as Foo;
// Class alias resolved at compile time as normal
<< Foo(time()) >>
class A {}

$class_reflection = new ReflectionClass('A');
$annotations = $class_reflection->getAnnotations();
foreach ($annotations as $annotation) {
    if ( $annotation->getClassName() == 'MyAnnotations\\FooAnnotation' ) {
        var_dump( $annotation->getArguments() ); // `time()` evaluated here
        var_dump( $annotation->getInstance() ); // `new 
MyAnnotations\FooAnnotation(time())` evaluated here
    }
}

It's not the responsibility of the ReflectionAnnotation class to worry 
about calling the autoloader, issuing errors, etc, it should just 
delegate that to the engine like any other constructor call. There's no 
need for an extra $annotation->classExists() method, either, because you 
can just say "class_exists($annotation->getClassName())".


Interestingly, this same delayed evaluation of arguments opens us up to 
include direct access to the AST as some (Nikita?) have asked for:

// Constructor argument can be any valid expression,
// however nonsensical it would be to evaluate it directly
<< Pre($a >= 42) >>
function foo($a) {}

$r = new ReflectionFunction('foo');
$annotations = $r->getAnnotations();
foreach ( $annotations as $annotation ) {
    if ( $annotation->getClassName() == 'Pre' ) {
        $ast = $annotation->getArgumentAST();
        // Now we can do funky things with the AST, like evaluating it 
in a custom context :)
    }
}


Regards,
-- 
Rowan Collins
[IMSoP]