fix ssr omitting bound attribute value 0

[jonniek]

#4551

Number 0 when used in the value of a binding was ignored by the server side rendering

This issue is most obvious on a non balanced range input with a default value of 0

<script>
    export let inputValue = 0
</script>

<input type="range" bind:value={inputValue} min="0" max="10" />

Before the fix this resulted in a ssr output with no input value which default to look like value 5. With the fix the ssr value is included which fixes the jump from 5 to 0 when client side code would render the input.

[Conduitry]

I haven't looked into what exactly is going on here, but at first glance it seems to me that the proper solution would be not to have a special rule about 0 but rather to not have add_attribute called with true for boolean at all.

[jonniek]

Ah that would make sense, I didn't think of trying that since I thought there might have been some important reason to use that flag.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.