Svelte 5: Allow classes to opt-in to deep reactivity about svelte HOT 4 OPEN

The reason not to go that route is that Grid (and Coord and many others) is a utility class that is used in many places, only some of which are reactive state.

One might say this is a userland problem and could be solved pretty robustly with a simple helper. Something like:

let reactiveObj = $state(deeplyMakeStateful(plainObj))

where deeplyMakeStateful walks the object tree and wraps appropriate fields in $state (using some mechanism like the proposal above).

And that does work, but now we're walking the object tree twice (worse performance) and adding boilerplate (unintuitive) wherever $state is involved. It seems like a win if we can provide a simple and lightweight built-in way to do this.

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Is Grid under your control? Or is this for classes not under your control?

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It is under my control. Is there a better alternative I'm missing?

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I guess the question then is, whether there is a reason not to make the fields of the class stateful?

Given the example thing:

class Thing {
-  foo: number;
+  foo = $state<number>();
-  bar: string;
+  bar = $state<string>();
}

(Would need assertions if you want to prevent undefined in the type.)

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