Allow hooks for backed readonly properties

[NickSdot]

wip
https://news-web.php.net/php.internals/127529
https://wiki.php.net/rfc/readonly_hooks

[Crell]

"nice"? 😄 Hooks are nice, but the term isn't descriptive in context.

[Crell]

This is close to what we want to confirm, but not quite. To match the RFC, we'd want a readonly Product class that contains public Category $category (possibly in the constructor?), then LazyProduct that extends it and adds a hook to do the lazy updating.

The intent here is that one can define a data model as just a boring readonly class, but then an ORM can code-generate a subclass that it will always use that handles the lazy initialization. That way it's all hidden from the author and user of the main class.

[NickSdot]

@Crell I pushed an update.

To be honest, I don't fully get this one. If something is generated, why the inheritance? Not trying to argue against though--I just don't get it, and hence have difficulties to be sure about what the test actually should look like. Any chance the update did land were you wanted it?

[Crell]

Yeah, that's a lot more what I was talking about.

The inheritance is for type compatibility. Consider you're writing a data-mapper ORM, like Doctrine. You want the developer to be able to define an object easily, without thinking about lazy loading or persistence. So they make a Product object. Because it's a read-model only (which is good; I've found separating the read model and write model is almost always a good decision), they make it readonly.

Then elsewhere in the system they have a function that takes a Product object as a parameter. They type it as Product and move on with life.

The ORM, though, wants to load things lazily. Say, references to other objects (like Category), or a list of other objects, or whatever. It can generate code that will do the lazy work in hooks (yay!), but then that function that expects Product won't accept it, because it's a LazyProduct rather than Product. The only way to resolve that is either to force interfaces on everything (which in this case is a needless burden) or to make the generated LazyProduct a child class of Product, so that it will pass type checks for Product. But then you're extending a readonly property and putting a hook on it, which you can't do.

... Until this PR. 😄