fix(yew-link): surface initial internal fetch errors instead of retrying indefinitely

[cuishuang]

Description

Fix the client-side use_linked_state retry loop caused by initial LinkError::Internal results not being cached.

Initial fetches now cache all completed results, including infrastructure errors. This allows the suspension to resolve and exposes the error through LinkedStateHandle::as_result() instead of creating another identical request.

Refresh behavior remains unchanged: LinkError::Internal results from background refreshes are not cached, so an existing stale value is preserved.

Fixes #4218

Checklist

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

[github-actions]

Visit the preview URL for this PR (updated for commit 80cd486):

https://yew-rs-api--pr4219-master-68tx4rnl.web.app

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[github-actions]

Size Comparison

Details

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	100.206	100.206	0	0.000%
boids	164.938	164.938	0	0.000%
communication_child_to_parent	93.710	93.710	0	0.000%
communication_grandchild_with_grandparent	105.993	105.993	0	0.000%
communication_grandparent_to_grandchild	102.314	102.314	0	0.000%
communication_parent_to_child	91.101	91.101	0	0.000%
contexts	106.300	106.300	0	0.000%
counter	86.271	86.271	0	0.000%
counter_functional	88.302	88.302	0	0.000%
dyn_create_destroy_apps	90.170	90.170	0	0.000%
file_upload	98.577	98.577	0	0.000%
function_delayed_input	94.617	94.617	0	0.000%
function_memory_game	168.581	168.581	0	0.000%
function_router	400.298	400.298	0	0.000%
function_todomvc	164.981	164.981	0	0.000%
futures	235.946	235.946	0	0.000%
game_of_life	100.623	100.623	0	0.000%
immutable	258.612	258.612	0	0.000%
inner_html	80.781	80.781	0	0.000%
js_callback	109.758	109.758	0	0.000%
keyed_list	176.339	176.339	0	0.000%
mount_point	84.192	84.192	0	0.000%
nested_list	112.731	112.731	0	0.000%
node_refs	91.776	91.776	0	0.000%
password_strength	1765.649	1765.649	0	0.000%
portals	93.599	93.599	0	0.000%
router	366.529	366.529	0	0.000%
suspense	113.938	113.938	0	0.000%
timer	88.518	88.518	0	0.000%
timer_functional	99.423	99.423	0	0.000%
todomvc	141.977	141.977	0	0.000%
two_apps	86.176	86.176	0	0.000%
web_worker_fib	136.490	136.490	0	0.000%
web_worker_prime	186.573	186.573	0	0.000%
webgl	82.927	82.927	0	0.000%

✅ None of the examples has changed their size significantly.

[cuishuang]

@WorldSEnder Modified. Please review it again.

[WorldSEnder]

Took a bit, since I am myself not familiar with this part of the library and was hoping Mado would chime in. So bear with and feel free to correct me too.

completed being an (unbounded) hashmap is I believe a memory leak (of all failed requests that never succeed). Keeping the old property of the LRU cache seems worthwhile.

I would phrase the property we want as follows: Every use of the use_linked_state hook has associated with it an input, call this the query. So when the input changes, the query does but it's the same hook. Every query should lead to at most one request to the backend (this is what I understand the bug is about). Multiple simultaneous queries from different uses of the hook for the same input should share the request (only one at best) - implemented by in_flight and refreshing. A query we already answered in SSR should lead to no request (subtly a different hook might have the same query without SSR, this can lead to a query request since cache is unreliable). And finally, memory should be proportional to the hooks used. After unmounting all, only a constant should be left, that's why LRU cache is used but HashMap is used only for things in flight.

The last property I think implies that two different hooks querying for the same input might not always share the result (which could have dropped out of the LRU already) and the hook needs to have a local cache, too.

EDIT: To come back to my earlier comment: each component should remember if a request failed and not retry again. The shared cache should be used only for successful requests.

Sorry this took so long, caching is hard.

[WorldSEnder]

Note: prior art for request coalescing in rs-singleflight could be helpful.