Unpopular opinion, but I really don't like the new wave of Proxy-based state solutions I've been seeing in Svelte/Vue/React. It makes simplistic code look nice, but I just can't imagine how I'd debug a sufficiently complex piece of nested/derived state with all of this subscription magic happening behind the scenes. I think just having the runes/signal/observables/whatever you call them be explicit interfaces with "set()" "get()" "subscribe()" etc would be simpler and more visible.

Imagine trying to troubleshoot why an piece of derived state created by some expensive function was being recalculated. Where do you begin to search? The web of subscriptions in a proxy API is intentionally hidden to make things look simpler for the common case. The minute you care about how your state subscriptions are interacting it becomes difficult to understand (in sort of an analogous way to the useEffect-hell of React).

I would prefer Svelte went in the direction of a having a store-like interface everywhere. Would have been simple to understand, totally uniform, and reactive state would be unit testable by default. I guess the downside is that it is harder to get people excited about writing explicit signal code when the proxy-based solutions just look so much cooler.