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 f940776):

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

_{(expires Sun, 12 Apr 2026 23:02:50 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	291.164	292.767	291.474	0.473
Hello World	10	482.353	484.209	483.122	0.662
Function Router	10	31515.489	31816.914	31667.039	98.340
Concurrent Task	10	1006.265	1007.636	1007.159	0.426
Many Providers	10	1086.974	1133.517	1110.302	18.670

Pull Request

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	291.168	291.584	291.383	0.131
Hello World	10	482.457	509.495	487.205	8.271
Function Router	10	31506.714	31975.390	31787.090	169.029
Concurrent Task	10	1006.404	1008.278	1007.183	0.555
Many Providers	10	1086.358	1206.664	1115.604	34.002

[github-actions]

Size Comparison

Details

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	99.932	99.932	0	0.000%
boids	163.820	163.820	0	0.000%
communication_child_to_parent	93.235	93.235	0	0.000%
communication_grandchild_with_grandparent	105.056	105.056	0	0.000%
communication_grandparent_to_grandchild	101.410	101.410	0	0.000%
communication_parent_to_child	90.646	90.646	0	0.000%
contexts	105.108	105.108	0	0.000%
counter	85.940	85.940	0	0.000%
counter_functional	87.975	87.975	0	0.000%
dyn_create_destroy_apps	89.865	89.865	0	0.000%
file_upload	98.949	98.949	0	0.000%
function_delayed_input	93.932	93.932	0	0.000%
function_memory_game	169.044	169.044	0	0.000%
function_router	398.069	398.069	0	0.000%
function_todomvc	164.068	164.068	0	0.000%
futures	234.660	234.660	0	0.000%
game_of_life	100.273	100.273	0	0.000%
immutable	257.886	257.886	0	0.000%
inner_html	80.463	80.463	0	0.000%
js_callback	109.086	109.086	0	0.000%
keyed_list	175.777	175.777	0	0.000%
mount_point	83.833	83.833	0	0.000%
nested_list	112.748	112.748	0	0.000%
node_refs	91.222	91.222	0	0.000%
password_strength	1718.438	1718.438	0	0.000%
portals	92.712	92.712	0	0.000%
router	364.772	364.772	0	0.000%
suspense	113.066	113.066	0	0.000%
timer	88.078	88.078	0	0.000%
timer_functional	98.567	98.567	0	0.000%
todomvc	141.759	141.759	0	0.000%
two_apps	85.804	85.804	0	0.000%
web_worker_fib	135.658	135.658	0	0.000%
web_worker_prime	184.060	184.060	0	0.000%
webgl	82.605	82.605	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  2.748 ns      │ 3.051 ns      │ 2.751 ns      │ 2.757 ns      │ 100     │ 1000000000

Pull Request

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.749 ns      │ 4.064 ns      │ 2.755 ns      │ 2.98 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.