Will a $derived in a context propagate reactive changes? LSP doesn't think so...

[Ruben-Kruepper]

I put a $derived into a context and the LSP warned me that it would only capture the initial value.

Is this intended? I would have expected the changes to propagate...

[brunnerh]

This is just how variables work in JS: You pass in whatever the variable references at that point in time.
If the variable changes later, the function you passed the value to will not know about it.

The solution is usually to pass a stateful object into the context, that way, the reactivity is contained within the object. Any mutation of properties can be reacted to.

If you need to pass a $derived, you can close over it, e.g.

let value = $derived(...);
setContext('key', () => value);
// or
setContext('key', {
  get value() { return value; }
});

Both of these reference the variable rather than taking the current value directly.

[Ruben-Kruepper]

Thanks for the clarification, I thought $derived was "more" than a value.

[brunnerh]

The compiler adds a wrapper around it, but any time you use the $derived, that is unwrapped, so it behaves pretty much like any other variable in plain JS contexts.