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 67c54e2):

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

_{(expires Tue, 21 Apr 2026 13:21:49 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	291.322	295.722	292.199	1.610
Hello World	10	490.974	498.228	494.394	2.468
Function Router	10	31582.986	32051.284	31795.879	178.854
Concurrent Task	10	1005.358	1008.298	1007.207	0.762
Many Providers	10	1099.999	1137.107	1113.567	12.600

Pull Request

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	294.474	307.257	298.394	4.076
Hello World	10	494.938	511.830	502.660	6.648
Function Router	10	31846.938	32278.908	32054.113	116.898
Concurrent Task	10	1007.809	1009.084	1008.295	0.367
Many Providers	10	1137.252	1176.647	1157.080	12.911

[github-actions]

Size Comparison

Details

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
actix_ssr_router	N/A	611.166	N/A	N/A
async_clock	100.054	100.054	0	0.000%
axum_ssr_router	N/A	611.165	N/A	N/A
boids	163.882	163.882	0	0.000%
communication_child_to_parent	93.483	93.483	0	0.000%
communication_grandchild_with_grandparent	105.467	105.467	0	0.000%
communication_grandparent_to_grandchild	101.821	101.821	0	0.000%
communication_parent_to_child	90.894	90.894	0	0.000%
contexts	105.709	105.709	0	0.000%
counter	85.742	85.742	0	0.000%
counter_functional	87.755	87.755	0	0.000%
dyn_create_destroy_apps	89.633	89.633	0	0.000%
file_upload	99.250	99.250	0	0.000%
function_delayed_input	94.374	94.374	0	0.000%
function_memory_game	169.549	169.549	0	0.000%
function_router	399.260	399.260	0	0.000%
function_todomvc	164.196	164.196	0	0.000%
futures	234.741	234.741	0	0.000%
game_of_life	100.489	100.489	0	0.000%
immutable	258.379	258.379	0	0.000%
inner_html	80.586	80.586	0	0.000%
js_callback	109.293	109.293	0	0.000%
keyed_list	175.911	175.911	0	0.000%
mount_point	83.953	83.953	0	0.000%
nested_list	112.851	112.851	0	0.000%
node_refs	91.469	91.469	0	0.000%
password_strength	1717.778	1717.778	0	0.000%
portals	93.107	93.107	0	0.000%
router	365.998	365.998	0	0.000%
suspense	113.165	113.165	0	0.000%
timer	88.326	88.326	0	0.000%
timer_functional	98.785	98.785	0	0.000%
todomvc	141.351	141.351	0	0.000%
two_apps	85.927	85.927	0	0.000%
web_worker_fib	136.226	136.226	0	0.000%
web_worker_prime	184.621	184.621	0	0.000%
webgl	82.729	82.729	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  2.459 ns      │ 2.484 ns      │ 2.464 ns      │ 2.465 ns      │ 100     │ 1000000000

Pull Request

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.459 ns      │ 2.654 ns      │ 2.467 ns      │ 2.47 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.

[Madoshakalaka]

I have reviewed this to the best of my effort.