maciejpedzi.ch/src/pages/rss.xml.js

import rss from '@astrojs/rss';
import { getCollection } from 'astro:content';
import { SITE_TITLE, SITE_DESCRIPTION } from '../consts';

export async function GET(context) {
  const posts = (await getCollection('blog')).sort(
    (a, b) => b.data.pubDate.valueOf() - a.data.pubDate.valueOf()
  );

  const { body } = await rss({
    title: SITE_TITLE,
    description: SITE_DESCRIPTION,
    site: context.site,
    items: posts.map((post) => ({
      ...post.data,
      link: `/blog/${post.slug}/`
    }))
  });

  return new Response(body, {
    status: 200,
    headers: {
      'Content-Type': 'application/rss+xml'
    }
  });
}