bug(svelte): useAskable.svelte.ts registers listeners without $effect — no automatic cleanup on unmount #267

Summary

In packages/svelte/src/useAskable.svelte.ts, focus and clear event listeners are registered synchronously at the top level of the function body, outside any $effect. A destroy() function exists to remove them, but callers must invoke it manually — typically in onDestroy. If they forget, listeners accumulate.

Current code

ctx.on('focus', handleFocus);   // registered at call time, not in $effect
ctx.on('clear', handleClear);

Cleanup only happens if the caller explicitly calls destroy():

function destroy() {
  ctx.off('focus', handleFocus);
  ctx.off('clear', handleClear);
  if (!usesProvidedCtx) ctx.destroy();
}

Expected behaviour

Svelte 5 runes expect side effects in $effect blocks so the runtime manages cleanup:

$effect(() => {
  const handleFocus = (f: AskableFocus) => { focus = f; };
  const handleClear = () => { focus = null; };
  ctx.on('focus', handleFocus);
  ctx.on('clear', handleClear);
  return () => {
    ctx.off('focus', handleFocus);
    ctx.off('clear', handleClear);
  };
});

destroy() can then be retained for explicit ctx teardown (unobserve, etc.) without needing to also handle listener cleanup.

Impact

Memory leak in any Svelte 5 app that unmounts components using useAskable without calling .destroy() explicitly.