eagerPreload: anchorUrl throws 'Invalid URL' on anchors not yet adopted into the page #704

Versions: @solidjs/router 2.0.0-next.42, @solidjs/web 2.0.0-rc.18, Chromium.

What happens

With preloadLinks: eagerPreload({ all: true }), the idle flush can throw:

TypeError: Failed to construct 'URL': Invalid URL
    at anchorUrl (dist/data/events.js:55)
    at ambientPreload (dist/preload.js:49)

eagerPreload claims anchors when they are created (claimAnchors, dist/preload.js:11) and preloads them at idle (:165). anchorUrl does new URL(href) with no base (dist/data/events.js:55).

Solid clones compiled nodes from a <template> (@solidjs/web dist/web.js:430-437). A clone belongs to the template's inert document, whose base is about:blank, so a.href is the raw attribute (e.g. /about) until the node is adopted into the page. If the idle flush runs before that, for example while a transition holds the new tree off the page, new URL("/about") throws, uncaught.

Browser check:

const t = document.createElement("template")
t.innerHTML = '<a href="/about">about</a>'
const a = t.content.firstChild.cloneNode(true)
a.href          // "/about": not resolved
new URL(a.href) // TypeError: Failed to construct 'URL': Invalid URL

Repro

1. createRouter({ preloadLinks: eagerPreload({ all: true }), ... }).
2. A route whose component renders <a href="/about"> next to an async memo that resolves after 1.5 s.
3. Load another page, wait for load, then navigate to that route client-side.
4. The idle flush runs while the new tree is still off the page, and the TypeError above is thrown.

Expected

An anchor that isn't connected is skipped (or stays queued) and is preloaded once it is in the page.

Suggested fix

In the flush, skip anchors with !a.isConnected (or keep them queued). In anchorUrl, resolve HTML anchors against document.baseURI, as is already done for SVG anchors.