$state array does not update on page back when reassigned

[0XPW87]

Describe the bug

When using the page back browser button, an array declared with $state is not reactive when using reassignment to change its value in firefox

Reproduction

let favourites = $state([])

onMount(() => {
     //this is a network promise in the actual code
     Promise.resolve({"favourites": [1, 2, 3]}).then(res => {


           //-----this causes the state to not update
           favourites = res["favourites"];
           //----


           //===but when using this, it works
           favourites.length = 0;
           for(let a of res["favourites"]){
                 favourites.push(a);
           }
           //====


     })
})

System Info

Observed only in firefox (my version - Mozilla Firefox 128.5.0esr)- not in chromium, AND only when "Disable cache" in network dev tools is turned off

Severity

annoyance

[paoloricciuti]

It seems to work fine

Please provide an actual reproduction, possibly in the REPL with a non working code. 😄

[0XPW87]

Hey,

thanks for the reply- as mentioned, this was only observed in firefox 128.5, when navigating back a page, AND having disabled network cache, so I presume you won’t see it in the playground with a non network request.

I don’t have my code with me (I can upload it later), but replacing the promise with a call to an endpoint returning that json is basically the entire code.

[paoloricciuti]

Closing to clean the issue queue a bit but feel free to reopen if you still experience this