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Date: Thu, 1 Jul 2021 18:05:17 +0200
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To: Larry Garfield <larry@garfieldtech.com>
Cc: php internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [VOTE] Readonly properties
From: deleugyn@gmail.com (Deleu)

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On Thu, Jul 1, 2021 at 5:25 PM Larry Garfield <larry@garfieldtech.com>
wrote:

> On Thu, Jul 1, 2021, at 9:49 AM, Pierre wrote:
> > Le 01/07/2021 =C3=A0 16:38, Nicolas Grekas a =C3=A9crit :
> > > Hi NIkita,
> > >
> > > I voted against the proposal because it doesn't work with cloning at
> all.
> > >
> > > Cloning is a critical feature of stateful objects, and we should solv=
e
> it
> > > the same version that introduces readonly IMHO.
> > >
> > > If we figure out that we can't agree on a sensible improved behavior
> for
> > > cloning, we're going to be in a dead-end with readonly.
> > >
> > I respectfully disagree.
> >
> > Having readonly properties and immutable objects is a must have, but
> > changing property of an object while cloning, not so much. There's many
> > case where readonly properties will be valuable where you never need to
> > clone your objects. Actually, cloning objects is not something you do
> > every day.
> >
> > Please note that I agree with you that advanced / flexible clone
> > semantics would be a nice to have, but I don't see the lack of it
> > blocking for readonly properties.
> >
> > I personally don't have any real use case where I couldn't implement
> > withers on my objects doing the same than dedicated advanced clone
> > semantics. Could you please provide some real world examples ? People
> > could change their minds if they could see why it's so blocking for you=
.
> >
> > Regards,
>
> The most famous use case right now for with-er objects is PSR-7, which is
> where the naming convention comes from.  I cannot say how widely used it =
is
> outside of FIG-inspired value objects, but I am pretty sure it is used.
>
> The key point is that you rarely need to clone service objects; value
> objects, however, you have to clone if you want to mutate.  Look at any
> PSR-7 pipleline.  By design, it calls $request->withBlah($newBlah) a lot,
> and returns a new object.  That's the model that we want to support, and
> make *easier* to do, but the readonly flag makes *harder* to do than the
> status quo today.  (See my previous post on the subject in the last threa=
d.)
>
> There are use cases for readonly that don't require cloning.  For those,
> it's useful.  I personally think asymmetric visibility would render
> readonly unnecessary and redundant, but Nikita disagrees, and he's the on=
e
> writing the code so... :-)
>
> The best case scenario is by 8.2 we end up with asymmetric visibility and
> clone-with, and combined with readonly we get a huge array of options for
> how to lock down value objects and still make them evolvable.  The worst
> case scenario is we find that readonly cannot be extended to support
> clone-with for some hand-wavy engine reasons, at which point it becomes
> largely vestigial in favor of asymmetric visibility and clone-with.
>
> --Larry Garfield
>
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>
>
I'd say don't use readonly on PSR-7. I have so many use cases for readonly
property and no use case for cloning. readonly syntax is far superior than
asymmetric visibility and will be almost as good as Constructor Promotion
Property. I would even go as far to say that I don't need anything more
than just readonly as-is. I think the bigger picture here is how many use
cases are there that would vastly benefit from this Vs how many use cases
could potentially benefit from it but won't because of lack of cloning
support. Of course everyone's opinion will be shaped by the universe they
live in and in mine this RFC covers everything I need with no drawbacks and
I honestly don't understand not wanting this just because of lack of
cloning.


--=20
Marco Aur=C3=A9lio Deleu

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