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Date: Sat, 28 Aug 2021 23:12:24 -0400
In-Reply-To: <CAJpLVh0Mi+cnA1UX+mFfSdDLAfDySLH-H9LkwomHCfa6CEnOrQ@mail.gmail.com>
Cc: Rowan Tommins <rowan.collins@gmail.com>,
 internals@lists.php.net
To: =?utf-8?Q?Olle_H=C3=A4rstedt?= <olleharstedt@gmail.com>
References: <CAJpLVh0i0mv=v7uGOAry4S3DAbYzJBhVyo-ziuki_Tdi-r+g9g@mail.gmail.com>
 <6074db02-5540-1831-e77d-0ed8f882a63e@gmail.com>
 <CAJpLVh0Mi+cnA1UX+mFfSdDLAfDySLH-H9LkwomHCfa6CEnOrQ@mail.gmail.com>
Subject: Re: [PHP-DEV] Make namespace part of runtime
From: mike@newclarity.net (Mike Schinkel)

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> On Aug 28, 2021, at 5:12 PM, Olle H=C3=A4rstedt =
<olleharstedt@gmail.com> wrote:
>=20
> 2021-08-27 23:07 GMT+02:00, Rowan Tommins <rowan.collins@gmail.com =
<mailto:rowan.collins@gmail.com>>:
>> On 27/08/2021 20:47, Olle H=C3=A4rstedt wrote:
>>> As a followup for my previous post, I think this could be a good =
place
>>> to start to enable attribute writers to create encapsulation =
mechanics
>>> for composition, like namespace visibility, "internal" access or
>>> friend classes.
>>=20
>>=20
>> In my experience PHP projects tend to use namespace hierarchies which
>> are deep rather than broad, and I'm not sure how easily those
>> hierarchies could be re-purposed as scopes.
>>=20
>> Clicking through the Symfony source at random for an example, I found
>> "namespace
>> Symfony\Component\Messenger\Transport\Serialization\Normalizer", =
which
>> contains only one class.
>>=20
>> A trivial implementation of namespace visibility which just matched =
the
>> exact namespace string would be completely useless for that class (it
>> would be the same as "private"). A slightly less trivial
>> implementationmight allow access from "child namespaces", but that
>> wouldn't help in this case.
>>=20
>> However, it might be really useful to restrict usage of that class, =
or
>> some of its members, to classes in the "Symfony\Component\Messenger"
>> namespace; or maybe to those in the
>> "Symfony\Component\Messenger\Transport\Serialization" namespace.
>>=20
>> I can see two ways of enabling that:
>>=20
>> - Allowing visibility modifiers to specify exactly what level of =
prefix
>> they refer to. This is apparently how Scala approaches things, =
allowing
>> you to write the equivalent of "private[Symfony\Component\Messenger]
>> $foo; protected[Symfony\Component\Messenger\Transport\Serialization] =
$bar;"
>=20
> Yes, I assume this is why Psalm introduced a new annotation
> @psalm-internal <namespace>, which does take such a parameter. A PHP
> attribute can do this, _if_ it has access to runtime namespace.
>=20
>> - Introducing a separate concept of "package", either orthogonal to
>> namespaces or overlapping with them, e.g. "package
>> Symfony\Component\Messenger; namespace
>> Transport\Serialization\Normalizer;" would still give a class name
>> beginning
>> "Symfony\Component\Messenger\Transport\Serialization\Normalizer", but
>> would define "internal" to mean accessible within the
>> "Symfony\Component\Messenger" package.
>=20
> What's the estimated effort for adding package support to PHP? Did
> anyone outline a possible implementation?

In case you have not seen these, which discuss possibilities but at a =
higher level than actually how to implement:

=
https://github.com/nikic/php-rfcs/blob/language-evolution/rfcs/0000-langua=
ge-evolution.md =
<https://github.com/nikic/php-rfcs/blob/language-evolution/rfcs/0000-langu=
age-evolution.md>
https://phpinternals.news/45 <https://phpinternals.news/45>=20

-Mike=

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