Tricky component binding blowback case

[Rich-Harris]

Via #721 — REPL. (An aside — there's a weird 'Cannot set read-only property' error happening in the REPL... currently only reproducible if you download it. Weird.)

The observer created in the Top.html component's oncreate hook causes everything to be updated while an update is already in progress, which is a problem. Not sure quite why it's resulting in that behaviour (list items being dropped) though.

I daresay this is one of the cases where two-way binding is dangerous. Svelte should still be able to handle it though.

@TehShrike one workaround is to change this...

this.observe('position', () => this.updateTop())

...to this:

this.observe('position', () => {
  Promise.resolve().then(() => this.updateTop());
});

[TehShrike]

Ah, trippy - that might actually cause some flickering in my use case, but I'll roll with that workaround once #728 goes out and see how it goes.

[Rich-Harris]

I think we're probably safe to close this given how differently v3 handles this stuff