Add `RouterLink` prop to provide `useLink` implementation

[8ctavio]

What problem is this solving

I am writing a component that wraps RouterLink, but I would like to use the useLink composable to easily access refs like isActive in the setup function.

In order to use both useLink and RouterLink in a single component, a new RouterLink prop could be introduced so that useLink's returned value may be provided instead of the to prop. The implementation can be easily achieved; the main concern would be updating RouterLinkProps type. An union could be used to define RouterLinkProps so that either to or the new prop are provided.

Apart from simplified link's consumption/access, I think another secondary benefit would be that if RouterLink gets unmounted (e.g., with v-if), useLink does not have to be called on every mount.

Proposed solution

<script setup>
const link = useLink()
// ... use link during setup
</script>

<template>
  <!-- Provide link implementation -->
  <RouterLink :link>

  </RouterLink>
</template>

Describe alternatives you've considered

1. Use useLink only: Requires rewriting part of RouterLink.
2. Use RouterLink only: Requires extracting its slot props from the template for use in the setup function, which is somewhat cumbersome, and they become available until the mounting phase.
3. Use both independently: Would create two different sets of computed values and functions that do the same, one for the setup function, and one for the RouterLink component.

[posva]

This sounds like a very specific case. I think an RFC process would highlight the required needs and alternative solutions. Right now, it sounds specific enough to be in a custom component rather than in Vue router. Try following the vuejs/rfcs repository process and open a discussion here instead please