Is there a way to get the underlying object from a state proxy?

[peterreeves]

Is there some way to get a reference to the underlying object from a state proxy? I was under the impression that $state.snapshot would just return the underlying object, but it looks like it clones or something instead? I also remember there being a $state.is rune at some point, though I can no longer find it in the documentation. Did it get removed?

const myObj = {
    val: 3
};

const stateObj = $state(myObj);

console.log(myObj === $state.snapshot(stateObj)); // Prints `false`

[brunnerh]

$state.is was removed and there is no way to get the object from the proxy as far as I know.
Why do you need it?

(This comment has more info on the removal.)

[peterreeves]

I trying to build my own deeply reactive version of Set (I'm rewriting an app from v3 to v5 and there's a few global Set stores that I'd like to switch to runes). But then I hit issues when trying to work out the logic for has.

import { SvelteSet } from "svelte/reactivity";

class DeepSet<T extends object> {
    s = new SvelteSet<T>();
    
    // Constructor and other details omitted
    
    add = (t: T): void => {
        // This works fine
        const wrapped = $state(t);
        this.s.add(wrapped);
    };

    has = (t: T): boolean => {
        // But what to do here?
        
        return this.s.has(t); // Won't work, stored values are wrapped in proxy
        
        const wrapped = $state(t);
        return this.s.has(wrapped); // Won't work, `$state` will create a new different proxy
    };

}

I then had the idea that if I switched out the internal SvelteSet for SvelteMap, I could use the base object as the key.

import { SvelteMap } from "svelte/reactivity";

class DeepSet<T extends object> {
    m = new SvelteMap <T, T>();
    
    // Constructor and other details omitted
    
    add = (t: T): void => {
        const raw = $state.snapshot(t); // Unwrap in case were given a proxy
        const wrapped = $state(t);
        this.m.set(raw, wrapped);
    };

    has = (t: T): boolean => {
        const raw = $state.snapshot(t); // Unwrap in case were given a proxy
        return this.m.has(raw);
    };

}

But that doesn't work either, since (to my surprise) $state.snapshot returns something different from what I thought it did.

[brunnerh]

Wrapping elements in a proxy internally does not seem very useful.
Wrapping does not affect the original object (and changes to the proxy also do not affect the original object).

[peterreeves]

Wrapping elements in a proxy internally does not seem very useful.

I realize the original object I pass in to add may or may not be reactive, but once I access it through the Set (Either from get or looping over all entries) I'd like it to be reactive.

Wrapping does not affect the original object (and changes to the proxy also do not affect the original object).

Ok, that's new to me. I swear I read somewhere in the documentation for v5 that updating a piece of state also updated the underlying object. But I guess that's not the case: https://svelte-5-preview.vercel.app/#H4sIAAAAAAAACkWPTQrCMBCFrzJEF4picVvTgAfwBOqixhGiaRKaSaGE3N2pRbp8P98bJouXsRhFfc3CtR2KWpxDEHtBY5hEHNASso4-9XpyZNS9CaRu7kYWCfzjDQ1kGFpbwxHK6R9onxxxtI7UEm64t-VMVgvv5CMReQfeaWv0p8mbLTRqJg88CLsGjkVd0rQgq7n9I_Pqg-NSLNNRGVTmKz8tq6D-3tKa3VwxywR_1fmneRl8ipr6hOVevrjSaNcQAQAA

Hrmm.... ok. Perhaps I need to rethink my approach here.
Thanks for your help.

[brunnerh]

This used to be the case, the behavior was changed in the same PR that removed $state.is.

[peterreeves]

Ahh, so I'm not going crazy after all 😅