Reactive `selected` prop

[cbenz]

I'm surprised to read in the docs that the selected prop is static ("[...] or passed as prop to set pre-selected options that will already be populated when the component mounts before any user interaction").

In my case, the selected options depend on the external context, the URL params, and when I go back/forward the MultiSelect has to update in consequence.

This worked as I expect with version 6.1.0 but since version 7.1.0, the selected prop has become static (it does not take new values into account).

Is this intended behavior?

As a workaround, I did use:

{#key selected}
  <MultiSelect {options} {selected} />
{/key}

Here is a quick-made REPL to demonstrate this: https://svelte.dev/repl/153f9049a9b849aa9fcc95117061a867?version=3.52.0

[janosh]

Thanks for bringing this up and for the nice REPL repro. This is not intended behavior. I'm pretty sure this is a consequence of #123 which added an extra layer in between the selected and what the component actually renders in order to have selected be a single option (instead of a length-1 array) if maxSelect={1}. Can't please everyone, I guess, eh @davipon? 😄

Seriously though, it's too bad I haven't found a good way of testing 2-way binding yet which would have prevented this regression.

[wd-David]

Thanks for bringing this up and for the nice REPL repro. This is not intended behavior. I'm pretty sure this is a consequence of #123 which added an extra layer in between the selected and what the component actually renders in order to have selected be a single option (instead of a length-1 array) if maxSelect={1}. Can't please everyone, I guess, eh @davipon? 😄

Yes, this is the consequence of #123. I was also preparing a repro of this 😊.

Seriously though, it's too bad I haven't found a good way of testing 2-way binding yet which would have prevented this regression.

Not sure if my svelte-component-test-recipes could help.
Even though I don't like the svelte-htm locked-in approach, it works anyway.

[janosh]

Yeah, I was just rereading your two-way binding recipe. Very cool that it works but it would require two new dependencies. I might just go with a wrapper component that dispatches events for testing whenever the two-way bound variable changes.

[janosh]

Maybe the best solution for regaining 2-way binding for selected is to create a new prop value which should only be used if maxSelect == 1 in which case it is selected[0]. If maxSelect != 1 it would be null to signal that this shouldn't generally be used. We could also set value = selected if `maxSelect != 1, not sure which is better.

The only problem with this is that you can't control value with 2-way binding (same as selected now), you'd have to use selected for that, even if maxSelect == 1. I don't currently see a way around that.

[janosh]

Released in v8.0.0. I confirmed that installing

import MultiSelect from "svelte-multiselect@8.0.0"

in your REPL fixes the issue.