🤔🤔🤔

svelte-2.html

<div on:click="set({ count: count + 1 })">
  {count} {double}
</div>

<script>
  export default {
    data() {
      return { count: 0 };
    },
    
    computed: {
      double: ({ count }) => count * 2
    }
  };
</script>

svelte-3.html

<script>
  let count = 1;
  const double = () => count * 2;
</script>

<div on:click="count += 1">
  {count} {double()}
</div>

Preload! We need to figure out how to support preload — doesn't need to be the exact same mechanism, but something like it. (We could abandon it in favour of doubling down on Suspense, but it wouldn't quite cover the same area.

In fact SSR more generally is a big unknown. In this new world, the initial setup code (which is currently what we'd call oncreate) always runs, on both client and server. onchange and onrender (or whatever) would never run. ondestroy could either be a noop (in which case any mount code would have to be wrapped in if (process.browser) or something), or it could be called immediately following render.

It's possible that we'd lose the API distinction between client and server. We could also consider introducing async SSR rendering. Lot of possibilities, lot of stuff to figure out.

Oh, and all this needs to work with standalone components as well as normal ones