feat: omit trailing $.sibling calls where possible

[Rich-Harris]

Given this input...

<div>
  <p>{dynamic}</p>
  <p>static</p>
</div>

...we generate this output:

export default function App($$anchor) {
  var div = root();
  var p = $.child(div);

  p.textContent = dynamic;
  $.sibling(p, 2);
  $.reset(div);
  $.append($$anchor, div);
}

The $.sibling(p, 2) call exists to preserve hydration state — if the container was an {#if true} block rather than a <div>, we would need to advance hydrate_node by 2 otherwise the next thing would try and hydrate the wrong nodes.

When there is a container element, we typically call $.reset(div) instead, meaning we don't actually need the $.sibling(...) call.

This does cause an issue with the hydration mismatch detection added in #12755, however (hence the test failures). Not sure what the most elegant solution would be.

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Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

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Latest commit: 2b30aff

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[trueadm]

Can't we wrap the $.sibling(p, 2); in a hydrating flag if we know it's identifier is never referenced so at least in the cases where we aren't hydrating we don't traverse all those nodes? We could probably group multiple traversal nodes together in a side if statement too.

[Rich-Harris]

We used to have a $.next() call that served a very similar purpose (it advanced hydrate_node and did nothing during mount). Can modify that for this case.

We could probably group multiple traversal nodes together in a side if statement

Not sure what this means?

[Rich-Harris]

closing for now, can revisit later if nec