Re: [RFC] Readonly property hooks

Thanks for your detailed thoughts, Claude. I'd like to offer my perspective on some of the points you raised. Le mer. 9 juil. 2025 à 12:53, Claude Pache <claude.pache@gmail.com> a écrit : > > > Le 8 juil. 2025 à 17:32, Nicolas Grekas <nicolas.grekas+php@gmail.com> a > écrit : > > I read Claude's concern, and I agree with Larry's response: the engine > already allows readonly to be bypassed using __get. The added hook doesn't > make anything more lenient. > > > It is true that readonly could be bypassed by __get(); but this is a > legacy behaviour, and you have to take an explicit step to make it > possible. For those unaware of the awful hack, here is a minimal test case: > > https://3v4l.org/N78An > > where the unset(...) is mandatory to make it “work”. > > Are we obligated to sanction shortcomings of legacy concepts in newly > introduced concepts that are supposed to replace them? Or can we do > something better? I’ve outlined in a previous email what I think is a > better design for such situation (namely an init hook). > > Also, the fact that __get() is not yet deprecated means that we can still > use the aforementioned hack until/unless we’ve implemented a proper > solution. In the worst case, you can still use a non-readonly hooked > property and document the intended invariants in phpdoc. > __get is certainly not legacy; removing it would break many use cases without proper alternatives. The behavior after unset() has been promoted to a language feature when readonly properties were introduced *because* it helps solve real world use cases. I've been asked recently by Gina if those use cases were covered by eg native lazy proxies. The answer is *no*, because native lazy proxies cover only part of the lazy-proxying domain: what remains is proxying by interface and proxying internal classes, and those require a way to proxy all property accesses, which is why magic methods are required. With the argument that __get can be used to implement the non-readonly-ness, we could also say that hooks are not needed, because they can be implemented using __get. Yet, language aesthetics are important, and we welcomed hooks for this reason. Being able to easily lazy-init thanks to hooks on readonly would be a welcome improvement to me. That being said, about your init proposal, I think that could work. I'd just do it a bit differently: instead of introducing a new "init" hook, I'd prefer having "set" mean "init" for readonly properties. But I know nothing about the engine on the topic so I can't comment on the feasibility aspect. I'll leave this to others. Just a word about using hooks vs __get for lazy-init: the really hard part when using __get is emulating the public/protected/private visibility rules. Hooks make this a non-issue. Yet hooks - unfortunately - can't be used as a generic lazy-init implementation because of their behavior related to references. That's another topic, but still related, to reinforce that __get is certainly not legacy. > > If a class is final and uses readonly with either hooks or __get, then > that's the original author's choice. There's no need for extra > engine-assisted strictness in this case. You cannot write such code in a > non-readonly way by mistake, so it has to be by intent. > > > Enforcing as strictly as possible its intended invariants is a good design > for a robust language. Yes, it implies that users cannot (or can hardly) > escape annoying constraints. For example, you can’t extend a final class, > even if you think that you have good reason for it, like constructing a > mock object. > That's not strictness when the root concept is already filled with conceptual holes... I'm surprised nobody ever proposed the concept of an *immutable* keyword, that'd be like readonly but that'd accept only also-immutable values. Until this happens, using readonly for that is a fallacy I'm sorry... To me that invalidates all related arguments. Nicolas