Add useful methods to UseStateHandle & UseReducerHandle

[its-the-shrimp]

Description

This PR adds:

• UseStateHandle::get & UseReducerHandle::get that return the contained value of the handle in the form in which it's stored internally: in an Rc; These 2 methods will make it easier to work with non(-trivially)-clonable types in said containers;
• UseStateHandle::into_inner & UseReducerHandle::into_inner that consume the handle and return its 2 main parts: the inner value and the setter/dispatcher associated with the handle. These methods will allow for avoiding cloning in certain contexts where one would have to use get() + setter()/dispatcher() otherwise.

Checklist

• I have reviewed my own code
• I have added tests

[github-actions]

Visit the preview URL for this PR (updated for commit 174d139):

https://yew-rs-api--pr3422-add-handle-methods-dx5xc4eu.web.app

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[github-actions]

Benchmark - SSR

Yew Master

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	360.013	360.211	360.098	0.074
Hello World	10	687.706	696.796	691.000	2.394
Function Router	10	2172.100	2202.425	2185.140	8.032
Concurrent Task	10	1006.855	1008.117	1007.461	0.391
Many Providers	10	1576.487	1608.791	1590.125	11.505

Pull Request

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	359.987	360.105	360.055	0.035
Hello World	10	691.831	697.689	694.551	1.934
Function Router	10	2210.087	2235.343	2227.472	7.332
Concurrent Task	10	1006.772	1007.782	1007.408	0.401
Many Providers	10	1593.305	1638.931	1606.330	13.944

[github-actions]

Size Comparison

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	102.886	102.886	0	0.000%
boids	175.667	175.667	0	0.000%
communication_child_to_parent	95.304	95.304	0	0.000%
communication_grandchild_with_grandparent	109.031	109.031	0	0.000%
communication_grandparent_to_grandchild	105.724	105.724	0	0.000%
communication_parent_to_child	92.786	92.786	0	0.000%
contexts	113.452	113.452	0	0.000%
counter	89.195	89.195	0	0.000%
counter_functional	89.932	89.932	0	0.000%
dyn_create_destroy_apps	92.369	92.369	0	0.000%
file_upload	103.515	103.515	0	0.000%
function_memory_game	174.644	174.642	-0.002	-0.001%
function_router	352.274	352.280	+0.006	+0.002%
function_todomvc	163.509	163.509	0	0.000%
futures	227.443	227.443	0	0.000%
game_of_life	112.218	112.218	0	0.000%
immutable	188.789	188.789	0	0.000%
inner_html	85.979	85.979	0	0.000%
js_callback	113.463	113.467	+0.004	+0.003%
keyed_list	201.207	201.207	0	0.000%
mount_point	89.186	89.186	0	0.000%
nested_list	114.614	114.614	0	0.000%
node_refs	96.289	96.289	0	0.000%
password_strength	1721.318	1721.318	0	0.000%
portals	98.365	98.365	0	0.000%
router	318.267	318.271	+0.004	+0.001%
simple_ssr	144.242	144.240	-0.002	-0.001%
ssr_router	390.032	390.034	+0.002	+0.001%
suspense	119.012	119.012	0	0.000%
timer	91.795	91.795	0	0.000%
timer_functional	100.472	100.476	+0.004	+0.004%
todomvc	143.688	143.688	0	0.000%
two_apps	89.896	89.896	0	0.000%
web_worker_fib	138.877	138.875	-0.002	-0.001%
web_worker_prime	190.394	190.399	+0.006	+0.003%
webgl	88.551	88.551	0	0.000%

✅ None of the examples has changed their size significantly.

[ranile]

Can we avoid the transmute somehow?

[its-the-shrimp]

not really, this transmute converts between Rc<UseStateReducer<T>> and Rc<T>, there's not much you can do with a value inside an Rc

[kirillsemyonkin]

You would need to convert Rc<UseStateReducer<T>> -> Rc<T> (assuming T is not guaranteed to be Clone) some other way then (maybe via Any?). I think using repr(transparent) was a brilliant idea for Rcs and now I hope Rust makes it like a safe trait / Rc function.

[futursolo]

I am not in favour of this pull request.

We have discussed in some previous pull requests. How a state is stored should be an implementation detail. Not exposing this allows us to switch the underlying implementation at a later time.

e.g.:
To implement concurrent mode, we will need to have multiple schedulers and states need to be associated with a scheduler ID .
I am not exactly settled on how this would be associated.
This pull request rules out the following possibility.

struct UseStateReducer<T> {
    inner: T,
    scheduler_id: Id,
}

[its-the-shrimp]

The PR does restrict the flexibility in implementation, but on the other hand, how likely is the implementation to change? The current approach works just fine, obtaining/setting the value doesn't require much indirection, and the new methods will allow for easier usage of non(-trivially)-clonable types in the aforementioned handle types.

[kirillsemyonkin]

@futursolo Provide other solutions of being able to encapsulate/not clone setter/dispatcher in Yew then.

1. This PR is best case, since it being tied to implementation helps users to have an easy optimization path and easy access to the current value in a familiar Clone wrapper (which is being used for Reducible by the way).

2. Medium case is introducing a custom wrapper type UseStateValue<T> instead of giving the Rc<T> to the user. This type may contain your wanted scheduler_id, should be able to be Clone as UseStateHandle is, while not forcing clones of setter/dispatcher upon the users, as well as allowing the developer to not give power of changing parent's state to children.

#[derive(Clone, ...)] // also ImplicitClone
struct UseStateValue<T> {
    inner: Rc<T>, // using same `repr(transparent)`/`transmute` trick
}

impl Deref for UseStateValue<T> {
    type Target = T;
    ...
}

3. Worst case is adding custom wrapper type UseStateValue<T> that simply wraps UseStateHandle<T>. This type will not contain .set, but it will still be including setter/dispatcher via UseStateHandle<T>. It will also not be allowed in functions as an argument where Rc<T> parameter is required (functions trying to support this will need to have a impl Deref<Target = T> parameter instead) (medium case also suffers from this).

4. Even worst-er case is not doing anything and making users implement the worst case themselves.

Also possible that use_state will change so much in future that it might not even allow to get a value out of it as easily as Deref (e.g. callback access only). In such case this PR is quite benevolent, since these changes will vanish at that point as well.

[ranile]

The medium case isn't good because oftentimes the value needs to be cloned after getting it out of the state, forcing T to be Clone when it can be avoided. It's either that or recreating the Rc that we just took the value out of.

Yew playground has a component that suffers from this exact same thing today when attaching the change listener to Monaco editor

---

Concurrent mode, when implemented, will most likely come with breaking changes of its own. I'd rather remove these methods then, providing a suitable alternative, than not add them in the first place