maciejpedzi.ch/src/components/NavLink.astro

---
import type { HTMLAttributes } from 'astro/types';

type Props = HTMLAttributes<'a'>;

const { href, class: className, ...props } = Astro.props;

const { pathname } = Astro.url;
const isActive = href === pathname || href === pathname.replace(/\/$/, '');
---

<a href={href} class:list={[className, { active: isActive }]} {...props}>
  <slot />
</a>

<style>
  a.active {
    color: #fff;
  }
  a.active,
  a.active + a,
  a:hover + a,
  a + a:hover {
    border-left-color: #fff;
  }
</style>