Experiment with a structless variant of Yew

[futursolo]

Description

#2282 discusses the possibility of removing struct components. There are opinions that are both in favour of removing struct components and keeping them. However, there was no proof of concept that demonstrates what would be possible if function component becomes the only supported component type.

This pull request provides a prototype for #2282.
I do not expect this pull request to be merged, this is purely for demonstration purpose.

Currently I have only verified the function_router example and benchmark_ssr works.

A short summary:

1. Lifecycles are no longer boxed

This removes many allocations.
Lifecycle events are now pure function calls and commits immediately regardless of whether being an element or component. Previously, components commit at a later lifecycle events because we need to make sure parent state is not borrowed, function components do not have this requirement.
Hence, many workarounds currently used by hydration (priority rendering, etc.) can be removed.

This is possible because the lifecycle events are much simpler for function components and they do not need to mutably borrow any parent state.

2. Many boxed types and generics are removed

Mounting a component now involves 1 allocation (Rc<ScopeInner>).
Re-render does not involve any allocations (after Html is created.).

The function_router example is now ~40KB smaller.

3. SSR no longer needs to run any lifecycle events.

The hello world SSR benchmark is 100% faster than master branch.

4. Component states are no longer maintained via reference cycles.

Checklist

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

[github-actions]

Visit the preview URL for this PR (updated for commit c31c47b):

https://yew-rs-api--pr2957-structless-o27nw8px.web.app

_{(expires Fri, 18 Nov 2022 04:52:04 GMT)}

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[github-actions]

Size Comparison

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	108.628	N/A	N/A	N/A
boids	172.869	N/A	N/A	N/A
communication_child_to_parent	92.510	N/A	N/A	N/A
communication_grandchild_with_grandparent	107.214	N/A	N/A	N/A
communication_grandparent_to_grandchild	103.091	N/A	N/A	N/A
communication_parent_to_child	89.613	N/A	N/A	N/A
contexts	109.892	N/A	N/A	N/A
counter	87.522	N/A	N/A	N/A
counter_functional	88.000	81.056	-6.944	-7.891%
dyn_create_destroy_apps	90.384	N/A	N/A	N/A
file_upload	102.066	N/A	N/A	N/A
function_memory_game	165.372	145.061	-20.312	-12.282%
function_router	349.626	306.534	-43.092	-12.325%
function_todomvc	160.147	143.255	-16.893	-10.548%
futures	224.212	N/A	N/A	N/A
game_of_life	107.047	N/A	N/A	N/A
immutable	184.616	N/A	N/A	N/A
inner_html	84.129	N/A	N/A	N/A
js_callback	113.431	103.745	-9.686	-8.539%
keyed_list	198.051	N/A	N/A	N/A
mount_point	87.132	N/A	N/A	N/A
nested_list	114.165	N/A	N/A	N/A
node_refs	95.006	N/A	N/A	N/A
password_strength	1549.240	N/A	N/A	N/A
portals	98.516	N/A	N/A	N/A
router	319.420	N/A	N/A	N/A
simple_ssr	154.111	142.482	-11.629	-7.546%
ssr_router	394.614	342.947	-51.667	-13.093%
suspense	111.245	101.676	-9.569	-8.602%
timer	90.408	N/A	N/A	N/A
todomvc	141.444	N/A	N/A	N/A
two_apps	88.192	N/A	N/A	N/A
web_worker_fib	154.501	N/A	N/A	N/A
webgl	86.819	N/A	N/A	N/A

⚠️ The following examples have changed their size significantly:

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
counter_functional	88.000	81.056	-6.944	-7.891%
function_memory_game	165.372	145.061	-20.312	-12.282%
function_router	349.626	306.534	-43.092	-12.325%
function_todomvc	160.147	143.255	-16.893	-10.548%
js_callback	113.431	103.745	-9.686	-8.539%
simple_ssr	154.111	142.482	-11.629	-7.546%
ssr_router	394.614	342.947	-51.667	-13.093%
suspense	111.245	101.676	-9.569	-8.602%

[github-actions]

Benchmark - SSR

Yew Master

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	338.514	366.697	345.306	10.115
Hello World	10	637.161	643.690	639.028	2.126
Function Router	10	2240.224	2258.750	2245.693	5.697
Concurrent Task	10	1007.731	1009.692	1009.036	0.571

Pull Request

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	336.656	342.566	338.212	1.822
Hello World	10	293.208	297.767	294.923	1.527
Function Router	10	1766.444	1824.582	1782.136	18.528
Concurrent Task	10	1007.561	1008.882	1008.248	0.418