Is there a mechanism to construct a URL pathname from a routeId and params?

[georgecrawford]

Given that we have event.routeId and page.routeId now (PR), I'm wondering what the most friendly and idiomatic way is to construct a URL path to point to a route with the correct params?

Is there an easy way to take const routeId = "blog/archive/[page=integer]" and const params = {page: 199} to form the pathname /blog/archive/199, for example?

If not, this would be a lovely addition to SvelteKit for developer ergonomics. It'd also be nice to determine whether the current value of $page.routeId matches a link's href.

What I guess I'm working towards is something like this:

<Link routeId='blog/archive/[page=integer]' params={{page: 199}}>go to page 199</Link>

... which internally would do:

<script>
    export let routeId;
    export let params;
    const path = getPathForRouteWithParams({routeId, params});

    const current = path === $page.url.pathname; 
    // OR: 
    const current = (routeId === $page.routeId) && (isEqual(params, $page.params));
</script>

<a href={path} class:current={current}><slot /></a>

interested in thoughts from @Rich-Harris and @Conduitry as contributors to the routeId PR. Thanks!