Marco Pivetta wrote on 05/11/2014 14:02:
For example, this alternative approach perfectly fits the current
doctrine/annotations use-case:
use Doctrine\ORM\Mapping\Entity;
use Doctrine\ORM\Mapping\Table;
use Doctrine\ORM\Mapping\Id;
use Doctrine\ORM\Mapping\GeneratedValue;
use Doctrine\ORM\Mapping\Column;
[Entity::class => []]
[Table::class => ['name' => 'foo_table']]
class Foo
{
[Id::class => []]
[GeneratedValue::class => [GeneratedValue::UUID]]
[Column::class => ['name' => 'bar_column', 'type' => 'string']]
private $bar;
}
I did nothing special here, just using plain old associative arrays and
built-in `::class` pseudo-constants: this leaves space for libraries that
do want to use annotations, but not the way doctrine/annotations does it
(calling the constructor of an annotation), and the annotations themselves
can still decide what to do with nested values.
No autoloading is going on, no code execution, nothing: plain and simple
arrays which may as well be used for phpdocumentor as well, if needed.
One problem with using *just* array syntax, without any new keyword or
symbols, is that it is extremely close to being existing valid syntax.
This may well cause problems in the parser, and would certainly be
confusing to users.
Specifically, a class annotation might look like this:
['Blah\\Annotation\\Table' => ['name' => 'foo_table']]
class Foo {
}
But add a single semi-colon, and you have valid PHP code
[http://3v4l.org/inkul]:
['Blah\\Annotation\\Table' => ['name' => 'foo_table']];
class Foo {
}
This works because an expression, by itself, is a valid statement, as
long as it's terminated with a semi-colon, and before the "class"
keyword, you are just in global execution scope (a problem many other
languages don't have to worry about, because statements can't exist
outside blocks).
The same reasoning rules out simple uses of @ as the prefix, because
this is also valid code [http://3v4l.org/TCBbC]:
@Blah\Annotation\Table( ['name' => 'foo_table'] );
class Foo {
}
Amusingly, the @ suppresses the non-existent function error, making this
look almost like it "worked".
Having a single semi-colon change an annotation into a silent statement
seems like an extremely bad idea. The "inside" of an annotation can look
like an array or constructor call, but we need something distinct to
introduce (or wrap) it, assuming we want it positioned before the
"class" keyword, as in other languages.
Regards,
--
Rowan Collins
[IMSoP]
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