Ensure cloning of incomming data

[petterek]

Please verify syntax

[Conduitry]

Relevant comments in Gitter

[petterek]

Yes they are :) hopefully..
I think cloning of incomming data makes sense, to be able to detect chagnes, in case of date changing within the data itself, and then telling the component to update itself

[Conduitry]

Oof, making updates to branches on forks is not the most ergonomic experience, but at least I know how to do it now :)

Fixed the syntax, and updated the tests. Thanks for the suggestion @petterek

[Rich-Harris]

Thanks for the PR @petterek. I read the Gitter convo but I'm not entirely clear on what bug this is fixing? I ask because it would probably be preferable not to call assign for every component (since that includes nested components, which could number in the thousands) unless there's no other solution.

[petterek]

It might be i'm missusing svelte.. :) but..
If you change on of the fields of your data directly, without using component.set() and then try to use the set method to "rerender" the view. Svelte will not "detect" the change the first time, but.. the next time it wil.
The issue is only "visible" if you have no data() on the component.. So the cloning is already there but not if the data() is null.

I can fix my issue by letting the data() of the component return an empty object.

[Rich-Harris]

That's odd... can you create a repro?

[Conduitry]

@Rich-Harris I am actually able to reproduce what I think @petterek is referring to - https://gist.github.com/Conduitry/22dc70fcca81f5836989bd750c35baa0 - The app continues to render '0' and not '42'. If I include a <script> export default { data() { return {} } } </script> in the component, then this works correctly.

[Rich-Harris]

Ah, got it, thanks. Understand the problem now. Definitely a bug that needed to be fixed — I think at some point we might want to have a slightly different initialisation process for nested versus root-level components, so that we can assign where we need to and skip it where we don't, plus any other differences that exist between them (e.g. the order of operations is slightly different viz rendering). Will park that for now though.

Thanks for the fix @petterek 👍

[Rich-Harris]

PS I added a test based on @Conduitry's gist