`dynamic()` / `Dynamic` with a string tag: no `runHydrationEvents()`, namespace ignores parent

[ryansolid]

Version: 2.0.0-rc.8 (@solidjs/web)

Two correctness gaps in the string-tag branch of dynamic() (packages/web/src/index.ts ~366–374), which Dynamic uses:

case "string":
  const el = sharedConfig.hydrating
    ? getNextElement()
    : createElement(component as string, untrack(() => (props as any).is));
  spread(el, props);
  return el;

1. Hydration event replay never runs

Compiled JSX emits _$runHydrationEvents() after any element with event handlers (babel-plugin/src/dom/element.ts ~323). dynamic() binds handlers through spread(el, props) and never calls it. Events queued by the hydration header script for a <Dynamic component="button" onClick=…> are replayed only if some other compiled element on the page happens to call runHydrationEvents() after it hydrates; if the interactive elements are all Dynamic, queued clicks are dropped until _$HY.done. @yak/solid had to add the call in its own element renderer.

Fix: call runHydrationEvents() after spread when hydrating (cheap — it's a no-op when nothing is queued).

2. Namespace is chosen from the tag alone

createElement(tag) picks the namespace via SVGElements.has(tag) / MathMLElements.has(tag). Tags that exist in both HTML and SVG — a, script, style, title — are always created as HTML, so <svg><Dynamic component="a"> produces an HTML anchor inside an SVG tree. The compiler resolves this from the parent at build time; the runtime path has no parent context. This is why @yak/solid carries an ambiguousSvgTags set and routes those four tags differently.

Fix options: (a) accept the namespace from the mount context — insert/the parent element is known at spread time (el.parentNode after insertion is too late; a context or an explicit ns option would work); (b) at minimum document the limitation and expose the set so libraries don't hard-code it.

Related

• Perf: with a constant string tag dynamic() still allocates a factory memo and a per-instance memo to track a tag that can't change — tracked in Constant-tag Dynamic / dynamic() should take the compiled-element path #3387 and the perf tracker Perf tracker: Solid primitives vs the hand-rolled @yak/solid runtime #3389.
• Surfaced by the @yak/solid audit (DigitecGalaxus/next-yak#644).

[ryansolid]

Part 1 (runHydrationEvents() after dynamic() spreads a string tag) landed on next in 1af28a1 via #3396. Part 2 — a / script / style / title taking their namespace from the tag alone — remains open here.

— Claude via Cursor

[ryansolid]

Part 2 landed on next in c452850 via #3436, so both halves of this issue are now fixed.

dynamic() / Dynamic with a tag-name source now honors an xmlns prop when creating the element, the same attribute compiled JSX uses for the same purpose: <svg><Link xmlns="http://www.w3.org/2000/svg" href=…/></svg> with Link = dynamic(() => "a") creates an SVG anchor. Like is, it is read once, untracked, at creation and then applied as an ordinary attribute, so client-rendered output matches what the server serializes. Without xmlns the namespace is still inferred from the tag name.

Types: xmlns is accepted on the four HTML/SVG-ambiguous tags (a, script, style, title) in addition to the SVG/MathML attribute sets that already had it; unambiguous HTML tags still reject it.

Covered by test/dynamic-namespace.spec.tsx, test/server/dynamic-xmlns.spec.tsx, and the parity-harness scenario dynamic-xmlns-svg-link (SSR → hydrate → update).

— Claude via Cursor