fix(solid-router): don't install intent-preload listeners when preloading is off

[russelgal]

Problem

useLinkProps assigns the preload handlers unconditionally (link.tsx):

linkProps.onClick = onClick
linkProps.onBlur = onBlur
linkProps.onFocus = onFocus
linkProps.onMouseEnter = onMouseEnter
linkProps.onMouseOver = onMouseOver
linkProps.onMouseLeave = onMouseLeave
linkProps.onMouseOut = onMouseOut
linkProps.onTouchStart = onTouchStart

The preload check lives inside the handlers (if (preload() !== 'intent') return), so with preloading off they are still attached and still fire — they just return.

That is not free. Solid's DelegatedEvents set does not include mouseenter, mouseleave, focus or blur (they don't bubble), so assignProp installs a real addEventListener per anchor for each of them. click, mouseover, mouseout and touchstart are delegated and cost nothing.

Net effect: four listeners per <Link> that do nothing at all whenever preload is false, 'viewport' or 'render'.

I hit this on a booking board where every row is a link. Measured in Chrome on a real page, counting addEventListener calls for one client-side navigation onto the screen:

	listeners
165 rows rendered with <Link preload={false}>	660 (blur/focus/mouseenter/mouseleave × 165)
same rows, handlers not attached	0

Fix

Resolve those props through getters (the file already relies on this: "values that no longer apply resolve to undefined, which spread()/assign() treats as attribute removal"). With intent preloading off, the property yields whatever the consumer passed — or undefined, and nothing gets attached:

const onIntent =
  (composed: (event: any) => void, user: () => unknown) => () =>
    preload() === 'intent' ? composed : user()

Behaviour is unchanged:

• preload: 'intent' — identical to before.
• 'viewport' — preloading runs through the IntersectionObserver; the events were already no-ops there.
• 'render' — preloading runs in an effect; same.
• A consumer's own onMouseEnter/onFocus/… still fires, because the getter falls back to it.
• Still reactive: flipping preload back to 'intent' re-runs the consuming spread(), which attaches the composed handler then (and assignProp removes a stale non-delegated listener before adding).

Tests

Added to tests/link.test.tsx, alongside the existing preload/IntersectionObserver ones:

• Router.preload="false" | "viewport" | "render" — no mouseenter/mouseleave/focus/blur listeners on the anchor (spying on HTMLAnchorElement.prototype.addEventListener).
• Router.preload="intent" — the listeners are installed, as before.
• Link.preload={false} with the consumer's own onMouseEnter/onFocus — both still fire.

Verified the new tests fail without the fix (3 of them) and pass with it.

Ran locally on solid-router-v2-pre:

• eslint src/link.tsx tests/link.test.tsx — clean
• tsc -p tsconfig.legacy.json — clean
• vitest run — 59 files, 870 passed / 2 skipped
• vitest run --mode server — 3 files, 4 passed

Changeset included (patch).

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[nx-cloud]

View your CI Pipeline Execution ↗ for commit a5eda23

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☁️ Nx Cloud last updated this comment at 2026-08-27 17:10:32 UTC