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Reply-To: erictnorris@gmail.com
Date: Sun, 13 Jul 2025 14:15:21 -0400
Message-ID: <CA+NMNO07Kxj5+Ta05Aq4GQJzYK6eyb3C_gYpreEbwNGRZNyGTA@mail.gmail.com>
Subject: Re: [PHP-DEV] [RFC] Readonly property hooks
To: Marc Bennewitz <marc@mabe.berlin>
Cc: internals@lists.php.net, Nick <php@nicksdot.dev>
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From: eric.t.norris@gmail.com (Eric Norris)

On Sun, Jul 13, 2025 at 2:00=E2=80=AFPM Marc Bennewitz <marc@mabe.berlin> w=
rote:
>
>
> On 13.07.25 18:17, Nick wrote:
>
>
> On 13. Jul 2025, at 20:38, Marc Bennewitz <marc@mabe.berlin> wrote:
>
> Hi Nick, Claude,
>
> Hey Marc,
>
> I think it's important to explicitly mark it as "this value will be store=
d in memory", I mean just silently caching the get hook could quickly lead =
to unexpected behavior. Like one would expect the value to be changed
>
> The most here made the argument that "a changing value from a readonly ge=
t hook" would be the unexpected behaviour.
> That=E2=80=99s why we ended up with the current =E2=80=9Calternative impl=
ementation 2=E2=80=9D. Please see my last answer to Rob for a fair example =
[1] .
>
> The current preferred alternative implementation covers both situations..=
.
>
> If a property is `readonly`:
> - you can set once
> - on read you always get the same (once computed) value back
>
> This is exactly the behavior I mean which is somehow unexpected if not ma=
rked explicitly as the result could be cached and the property value will n=
ever change.
>
> Not being able to write to something doesn't generally mean reading the v=
alue will never change. `get =3D> random_int(0, 100);`
>
> I don't want to say that the path we want to go with readonly being able =
to assume the value will never change is wrong but I think it's not clear f=
or the user and can be missed quickly - even with a test as you have to rea=
d the property multiple time to notice the difference.
>
>
> If a property is NOT `readonly`:
> - you can set often
> - on read you always get the fresh (often computed) value back
>
> I argue that this is a very easy mental model.
> I hope that voters agree on =E2=80=9Ccached may be implied by readonly=E2=
=80=9D, as Claude called it.
>
> All what I'm saying is that this behavior should be explicit and not appl=
ied implicitly on a readonly get hook.

I agree with Marc here, not surprisingly.

> To have an `init` hook doesn=E2=80=99t solve the get hook issue.
>
> As far as I understood the init hook it would still disallow readonly+get=
 but allow readonly+init and init would be called once the first time the p=
roperty gets read and the result would end up in the backing store.
>
> As a result you get the same behavior as `cached get` with the only diffe=
rence that you write `init =3D> random_int();` instead of `cached get =3D> =
random_int();`

Agreed. Nick, I am not sure how the init hook doesn't "solve the get
hook issue". As I understand it, the get hook issue is that get hooks
are not allowed on readonly properties. The init hook would be
identical to a "cached get" hook on a readonly property, so why
doesn't it solve the issue?

> Or did I misunderstand it?

I share the same understanding as you, Marc.

> The cached modifier I would expect to be an attribute applicable to any f=
unction which uses another cache store similar to how it's possible in pyth=
on to memorize function calls which would be a very different feature.
>
> As earlier answered to Claude [2], I seek to write less code. To introduc=
e a `cached` modifier voids this for no strong reason (please see =E2=80=9C=
mental model=E2=80=9D above).
>
> See above - and `init` is just once more character.

I was going to respond to this point earlier, but Marc beat me to it.
An "init" hook is one more character than a get hook, is explicit over
a get hook that works differently only for readonly properties, *and*
is far fewer characters than the explicit "cached" modifier get hook
option.

On top of that, as Claude mentioned an init hook provides the ability
to differentiate between a null property and an uninitialized property
- an init hook would only be called for uninitialized properties, so
no need for $this->foo ??=3D "bar".