feat: add yew-link crate for unified SSR/CSR data fetching

[Madoshakalaka]

Description

Closes #2649, whose lower-level half includinguse_prepared_state and use_transitive_state is already shipped

This PR implements the higher-level half of #2649: a yew-link crate that unifies SSR, hydration, and client-side data fetching behind a single hook.

The mentioned lower-level hooks already carry server-computed state to the client during hydration. But after that initial page load, client-side navigation requires a completely separate fetch path. This means every data-dependent component needs two code paths stitched together manually. yew-link closes this gap.

Implemented new crates proposed in the pr: yew-link and yew-link-macro

Overhauled ssr_router example, rewired to use yew-link instead of generating content inline. Demonstrates #[linked_state], LinkProvider, use_linked_state, Resolver::register_linked, and the axum handler, with full SSR-to-hydration state transfer and client-side nav fetching.

See the new website changes to understand the usage pattern

Comparison with Bounce's Query API

@futursolo's Bounce, whose Query API and use_prepared_query hook do overlapping but not identical work

yew-link has bounded cache: client-side cache uses lru::LruCache (default 64 entries, configurable via LinkProvider's cache_capacity prop). Dependency gated to wasm32 only.

yew-link has more granular code isolation as its #[linked_state] strips resolve() from WASM and Query::query() body is always compiled into WASM.

yew-link also provides better utility by its built-in linked_state_handler for axum.

Checklist

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

I have overhauled the ssr_router to use yew-link.

I have overhauled the ssr_router's E2E test too:

1. Directly visiting a post by its url post/0 receives a server-rendered page with no extra fetch requests.
2. vist the posts page first, click on the anchor of posts with the id 0, in-app navigation happens and fetch happens exactly once
3. the post contents in 1 and 2 match

---

I'm not sure how cargo release in our .github/workflows/publish.yml handles the two added new crates, but that's a matter for the future when when publish yew-link with yew 0.23

[github-actions]

Visit the preview URL for this PR (updated for commit ea2893a):

https://yew-rs--pr4027-yew-link-sylkdib6.web.app

_{(expires Sat, 14 Mar 2026 17:32:40 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

[github-actions]

Benchmark - SSR

Yew Master

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	310.814	312.194	311.215	0.503
Hello World	10	476.208	558.751	486.268	25.703
Function Router	10	33564.790	34401.247	34058.828	251.073
Concurrent Task	10	1005.712	1010.019	1007.411	1.055
Many Providers	10	1090.942	1134.014	1112.022	16.866

Pull Request

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	310.881	326.083	312.580	4.747
Hello World	10	470.182	482.226	472.702	3.610
Function Router	10	33566.539	34482.172	34002.710	320.369
Concurrent Task	10	1006.372	1007.562	1007.111	0.403
Many Providers	10	1055.180	1084.375	1067.169	10.023

[github-actions]

Size Comparison

Details

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	100.272	100.272	0	0.000%
boids	168.092	168.092	0	0.000%
communication_child_to_parent	93.487	93.487	0	0.000%
communication_grandchild_with_grandparent	105.264	105.264	0	0.000%
communication_grandparent_to_grandchild	101.606	101.606	0	0.000%
communication_parent_to_child	90.897	90.897	0	0.000%
contexts	105.172	105.172	0	0.000%
counter	86.282	86.282	0	0.000%
counter_functional	88.275	88.275	0	0.000%
dyn_create_destroy_apps	90.322	90.322	0	0.000%
file_upload	99.377	99.377	0	0.000%
function_delayed_input	94.376	94.376	0	0.000%
function_memory_game	172.944	172.944	0	0.000%
function_router	406.546	406.546	0	0.000%
function_todomvc	164.161	164.161	0	0.000%
futures	235.191	235.191	0	0.000%
game_of_life	104.732	104.732	0	0.000%
immutable	255.899	255.899	0	0.000%
inner_html	80.803	80.803	0	0.000%
js_callback	109.399	109.399	0	0.000%
keyed_list	179.744	179.744	0	0.000%
mount_point	84.175	84.175	0	0.000%
nested_list	113.068	113.068	0	0.000%
node_refs	91.523	91.523	0	0.000%
password_strength	1728.855	1728.855	0	0.000%
portals	93.036	93.036	0	0.000%
router	377.116	377.116	0	0.000%
suspense	113.500	113.500	0	0.000%
timer	88.641	88.641	0	0.000%
timer_functional	98.878	98.878	0	0.000%
todomvc	142.114	142.114	0	0.000%
two_apps	86.176	86.176	0	0.000%
web_worker_fib	136.152	136.152	0	0.000%
web_worker_prime	187.383	187.383	0	0.000%
webgl	83.224	83.224	0	0.000%

✅ None of the examples has changed their size significantly.

[github-actions]

Benchmark - core

Yew Master

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.091 ns      │ 2.123 ns      │ 2.093 ns      │ 2.097 ns      │ 100     │ 1000000000

Pull Request

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.092 ns      │ 3.347 ns      │ 2.11 ns       │ 2.594 ns      │ 100     │ 1000000000

[Madoshakalaka]

these flush turned out to be very neccessary. Without them the ssr tests fails.

When .click() fires on the element, yew's event delegation hasn't processed it yet (scheduler is deferred to the microtask queue). So the browser's default anchor behavior kicks in - it performs a real navigation to /posts, which crashes the test runner.

[Madoshakalaka]

I've done some external testing too

My work has an SSR Axum-Yew app totaling 40k+ lines of rust. I've patched the project's dependency to use yew-link and migrated a handful of bounce's use_prepared_query to yew-link and saw good code simplification and no test failure.