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 f92053d):

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

_{(expires Wed, 25 Mar 2026 11:27:10 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	291.214	291.988	291.512	0.281
Hello World	10	508.930	517.649	511.485	2.782
Function Router	10	31822.253	32811.588	32212.470	349.328
Concurrent Task	10	1006.547	1007.780	1007.249	0.426
Many Providers	10	1049.824	1071.616	1059.972	7.000

Pull Request

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	310.697	312.336	311.192	0.681
Hello World	10	485.232	499.397	489.343	4.074
Function Router	10	31532.614	32384.471	31949.893	232.827
Concurrent Task	10	1005.327	1007.812	1007.096	0.744
Many Providers	10	1072.584	1101.322	1086.480	9.448

[github-actions]

Size Comparison

Details

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	101.095	101.096	+0.001	+0.001%
boids	168.882	168.902	+0.021	+0.012%
communication_child_to_parent	94.509	94.513	+0.004	+0.004%
communication_grandchild_with_grandparent	106.351	106.350	-0.001	-0.001%
communication_grandparent_to_grandchild	102.692	102.689	-0.003	-0.003%
communication_parent_to_child	91.921	91.921	0	0.000%
contexts	106.411	106.414	+0.003	+0.003%
counter	87.231	87.232	+0.001	+0.001%
counter_functional	89.269	89.270	+0.001	+0.001%
dyn_create_destroy_apps	91.146	91.147	+0.001	+0.001%
file_upload	100.326	100.324	-0.002	-0.002%
function_delayed_input	95.241	95.240	-0.001	-0.001%
function_memory_game	174.099	174.112	+0.014	+0.008%
function_router	395.915	395.744	-0.171	-0.043%
function_todomvc	165.385	165.395	+0.010	+0.006%
futures	235.984	235.982	-0.002	-0.001%
game_of_life	105.532	105.533	+0.001	+0.001%
immutable	260.494	260.505	+0.011	+0.004%
inner_html	81.774	81.775	+0.001	+0.001%
js_callback	110.397	110.400	+0.003	+0.003%
keyed_list	180.710	180.707	-0.003	-0.002%
mount_point	85.147	85.147	0	0.000%
nested_list	114.091	114.095	+0.004	+0.003%
node_refs	92.521	92.521	+0.001	+0.001%
password_strength	1719.354	1719.396	+0.042	+0.002%
portals	93.992	93.994	+0.002	+0.002%
router	366.558	366.400	-0.157	-0.043%
suspense	114.395	114.402	+0.008	+0.007%
timer	89.369	89.370	+0.001	+0.001%
timer_functional	99.803	99.807	+0.004	+0.004%
todomvc	143.096	143.097	+0.001	+0.001%
two_apps	87.145	87.146	+0.001	+0.001%
web_worker_fib	137.045	137.046	+0.001	+0.001%
web_worker_prime	188.227	188.235	+0.009	+0.005%
webgl	83.920	83.921	+0.001	+0.001%

✅ None of the examples has changed their size significantly.

[github-actions]

Benchmark - core

Yew Master

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.175 ns      │ 2.296 ns      │ 2.179 ns      │ 2.181 ns      │ 100     │ 1000000000

Pull Request

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.125 ns      │ 2.198 ns      │ 2.128 ns      │ 2.131 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.