fix(router): skip link data prefetch for loaders with unexpired in-memory data

[wmertens]

What

Link data prefetch (intent/visible/commit) fetched q-loader-*.json for every loader on the target route. The only dedupe was the 5-second URL-keyed fetch cache, so hovering or scrolling past links re-ran route loaders on the server even when the loader's signal already holds fresh data client-side (within its expires window, default 2 min).

How

• New internal core helper _hasValidSignalValue(signal) reads a computed signal's validity (has a value, not invalidated by dependency changes or expires) without triggering a computation.
• The in-memory loader state (RouteStateContext) is threaded into the Link prefetch paths (Link handlers, the visible-link observer, and the post-nav observer refresh). prefetchRoute skips fetching any loader whose signal is still valid.
• The nav-time prefetchRoute call intentionally does not skip: navigation invalidates those signals and refetches them, so the warm-up is still used.
• The loader-data loop is extracted into prefetchLoaderData for direct unit testing (the isBrowser guard is compile-time in vitest).

Verification

• prefetch-route.unit.ts (new): fresh signals are skipped, invalidated/missing loaders are fetched; all fetched when no state is given.
• link-prefetch.unit.ts / link-component.unit.tsx: updated to assert the loader state is forwarded.
• pnpm tsc.check, pnpm api.update, pnpm build.core, pnpm test.unit (206 files / 3200 tests) all pass.
• Local browser e2e could not run due to a pre-existing Nix/npm Playwright version mismatch (nix browsers 1.57/rev 1200 vs npm 1.61/rev 1228); relying on CI for the e2e suite.

Security note: no new trust boundary — the change only skips client-initiated fetches based on client-local signal state; request construction is unchanged.

🤖 Generated with Claude Code

https://claude.ai/code/session_019cqZnyUrRaqBjTKaLQtUK3

[changeset-bot]

🦋 Changeset detected

Latest commit: 87e4382

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@qwik.dev/router	Patch
@qwik.dev/core	Patch
eslint-plugin-qwik	Patch
@qwik.dev/react	Patch
create-qwik	Patch

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commit: 87e4382

[Copilot]

⚠️ Not ready to approve

The new _hasValidSignalValue() helper can misclassify pending/error async computed signals as “valid,” which can incorrectly skip needed prefetch fetches.

Pull request overview

This PR optimizes @qwik.dev/router link-triggered loader-data prefetching by avoiding q-loader-*.json fetches when loader data is already available client-side (within the loader signal’s validity window), reducing unnecessary server work during hover/visible/commit prefetch strategies.

Changes:

• Added a core internal helper (_hasValidSignalValue) to detect whether a computed signal already holds a usable value without triggering computation.
• Threaded router in-memory loader state through link prefetch entry points and updated prefetchRoute to skip fetching loader data when signals are still valid.
• Added/updated unit tests and included a changeset for @qwik.dev/router and @qwik.dev/core.

File summaries

File	Description
packages/qwik/src/core/reactive-primitives/utils.ts	Adds _hasValidSignalValue() for checking computed signal cached-value validity without computing.
packages/qwik/src/core/qwik.core.api.md	Updates extracted API docs to include the new internal helper.
packages/qwik/src/core/internal.ts	Re-exports _hasValidSignalValue via core internal entrypoint.
packages/qwik-router/src/runtime/src/router-outlet-component.tsx	Passes RouteStateContext into link prefetch initialization.
packages/qwik-router/src/runtime/src/qwik-router-component.tsx	Threads loader state into link prefetch observer refresh calls.
packages/qwik-router/src/runtime/src/prefetch-route.unit.ts	Adds unit coverage for loader-data prefetch skipping behavior.
packages/qwik-router/src/runtime/src/prefetch-route.ts	Adds loader-state-aware skipping and extracts prefetchLoaderData helper.
packages/qwik-router/src/runtime/src/link-prefetch.unit.ts	Updates observer tests to assert loader state forwarding.
packages/qwik-router/src/runtime/src/link-prefetch.ts	Threads optional loader state through observer and prefetch calls.
packages/qwik-router/src/runtime/src/link-component.unit.tsx	Updates Link tests to assert loader state forwarding to prefetchRoute.
packages/qwik-router/src/runtime/src/link-component.tsx	Reads RouteStateContext and forwards loader state into prefetchRoute calls.
.changeset/olive-pandas-repeat.md	Adds patch changeset for router + core behavior change.

Review details

• Files reviewed: 12/12 changed files
• Comments generated: 1
• Review effort level: Low

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