Deduplicate if (detaching) checks for components with multiple root elements

[K4rakara]

Describe the bug

When creating a component with multiple root elements, Svelte currently checks detaching for every single root element. IE:

// Truncated for brevity, see REPL

// ...

function create_fragment(ctx) {
  // ...
  return {
    // ...
    d(detaching) {
      if (detaching) detach(h1);
      if (detaching) detach(t1);
      if (detaching) detach(h2);
      if (detaching) detach(t3);
      if (detaching) detach(h3);
    }
  };
}

// ...

When ran through Terser, that roughly becomes:

detaching && detach(h1),
detaching && detach(t1),
detaching && detach(h2),
detaching && detach(t2),
detaching && detach(h3);

This should be fairly simple to cut down to this:

if (detaching) {
  detach(h1);
  detach(t1);
  detach(h2);
  detach(t3);
  detach(h3);
}

... which roughly becomes this:

detaching && (
  detach(h1),
  detach(t1),
  detach(h2),
  detach(t3),
  detach(h3)
);

This is a really minor thing, but it should lead to slightly better bundle sizes for some users.

I'd be happy to fix this as a first pull request 😄

Reproduction

REPL

Logs

No response

System Info

I encountered this on the playground, so I suppose 3.42.3?

Severity

annoyance

[dummdidumm]

Since this is a synchronous code path I'd say there's no reason to not tweak this, so you can go ahead and create a PR if you want to 👍

[gtm-nayan]

#8763