On Wed, Feb 26, 2025, at 09:17, Rowan Tommins [IMSoP] wrote: > > > On 25 February 2025 23:31:25 GMT, tight.fork3...@fastmail.com wrote: > >On 2/25/25 4:51 PM, Rowan Tommins [IMSoP] wrote: > >> I actually started writing an RFC to rationalise some of this behaviour > > > >I'm glad I'm not the only one who considers this an issue worth pursuing! > > Sorry, I wasn't clear: I was looking at the existing typed vs untyped, > unrefined vs uninitialised mess, before property hooks even existed. > > > > > >> Here are some of the things that might happen as a result of > >> unset($foo->bar): > > > >I don't disagree that there's a lot of weirdness. But for better or worse > >that's where PHP is now - it's a fundamentally weird language. I think it's > >better to be consistently weird than to be inconsistently weird. > > My point is that it's *already* inconsistently weird. > > > > It would be inconsistent to allow unsetting some types of properties but > > not others, and which ones can and can't be unset are indistinguishable to > > a 3rd-party consumer. > > unset() can already have a bunch of different effects depending on the > implementation of the class. As well as __unset being able to do *absolutely > anything*, I missed from my list "readonly" properties, which reasonably > enough *always throw an error for unset*, just like hooked properties. > > > >I can't comment from an implementation perspective, but as a user of PHP I > >would expect unsetting a backed property to return the property the > >"uninitialized" state, and subsequent access would proceed as if it were the > >first access of the uninitialized property. > > An untyped property is currently never in the "uninitialised" state, only a > different "undefined" state. Presumably this inconsistency would need to be > preserved (for consistency) > > > >Unsetting a virtual property could simply do nothing, but not result in a > >fatal error. I don't think a warning is even necessary because no action is > >taken. > > I don't see how that would be useful. The user presumably expected it to do > *something*, so informing them that it didn't seems preferable to silently > ignoring their request. It would also be inconsistent: a virtual property > with no "set" hook throws an error when you try to set it, it doesn't > silently discard the value. > > > > > I certainly don't want to be required to define an unset hook for every > > single backed property; rather `unset()` should have a default behavior. > > I think you're focusing too closely on one use case, rather than all the ways > people will want to use hooked properties. Imagine you have two properties > which you want to keep in sync: setting either of them recalculates the > other, using set hooks. > > * It would be really surprising to the class author if a user of the class > could "reach in" and invalidate the state by calling unset() on one of the > properties. > * It would be really surprising to the user if doing so worked on one of the > properties, but silently did nothing on the other because it was implemented > as virtual. > * It might be appropriate for the class author to add "unset" hooks to both > properties, and for the user to see that unsetting one unset the other, just > as setting one sets the other. > > That's just one scenario, I'm sure there are others where you could picture > different expectations, particularly accounting for some of the other > behaviour of unset(). That's what I mean by it being hard to specify the > behaviour; nothing to do with the implementation. > > Regards, > Rowan Tommins > [IMSoP]
I do think it makes sense to have an unset hook though, so long as it is thought out well. For example, would the unset hook be called automatically during garbage collection? Is it only called via unset() or are there other cases where it could be called too? Regardless of how wise it is to unset from outside a class, doing the suggested workaround from inside the class seems a bit odd as well. — Rob
