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 and actix-web (gated by respective features)

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 0.24

[github-actions]

Visit the preview URL for this PR (updated for commit d4f595e):

https://yew-rs--pr4027-yew-link-ts30s1c0.web.app

_{(expires Tue, 14 Apr 2026 15:52:15 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	291.282	293.893	291.962	0.885
Hello World	10	505.239	512.654	507.483	2.427
Function Router	10	31637.535	31960.582	31830.565	93.154
Concurrent Task	10	1006.150	1007.736	1007.118	0.623
Many Providers	10	1303.776	1432.563	1336.258	38.909

Pull Request

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	291.266	295.971	291.864	1.448
Hello World	10	485.925	501.467	491.952	5.573
Function Router	10	31153.259	31970.499	31710.755	241.250
Concurrent Task	10	1006.156	1007.831	1007.104	0.603
Many Providers	10	1088.739	1194.718	1115.010	32.826

[github-actions]

Size Comparison

Details

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
actix_ssr_router	N/A	611.871	N/A	N/A
async_clock	99.933	99.933	0	0.000%
axum_ssr_router	N/A	611.872	N/A	N/A
boids	164.027	164.027	0	0.000%
communication_child_to_parent	93.359	93.359	0	0.000%
communication_grandchild_with_grandparent	105.338	105.338	0	0.000%
communication_grandparent_to_grandchild	101.696	101.696	0	0.000%
communication_parent_to_child	90.771	90.771	0	0.000%
contexts	105.584	105.584	0	0.000%
counter	85.941	85.941	0	0.000%
counter_functional	87.976	87.976	0	0.000%
dyn_create_destroy_apps	89.864	89.864	0	0.000%
file_upload	98.950	98.950	0	0.000%
function_delayed_input	93.931	93.931	0	0.000%
function_memory_game	169.575	169.575	0	0.000%
function_router	398.704	398.704	0	0.000%
function_todomvc	164.481	164.481	0	0.000%
futures	234.661	234.661	0	0.000%
game_of_life	100.274	100.274	0	0.000%
immutable	258.191	258.191	0	0.000%
inner_html	80.464	80.464	0	0.000%
js_callback	109.425	109.425	0	0.000%
keyed_list	175.892	175.892	0	0.000%
mount_point	83.833	83.833	0	0.000%
nested_list	113.023	113.023	0	0.000%
node_refs	91.347	91.347	0	0.000%
password_strength	1718.561	1718.561	0	0.000%
portals	92.836	92.836	0	0.000%
router	365.078	365.078	0	0.000%
suspense	113.531	113.531	0	0.000%
timer	88.079	88.079	0	0.000%
timer_functional	98.696	98.696	0	0.000%
todomvc	141.760	141.760	0	0.000%
two_apps	85.805	85.805	0	0.000%
web_worker_fib	135.942	135.942	0	0.000%
web_worker_prime	184.321	184.321	0	0.000%
webgl	82.606	82.606	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  2.625 ns      │ 3.879 ns      │ 2.642 ns      │ 2.686 ns      │ 100     │ 1000000000

Pull Request

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.466 ns      │ 3.301 ns      │ 2.482 ns      │ 2.496 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.