Fix pre-generated RSS URLs (#2443)

* Allow pre-generated urls to be passed in rss feeds

* Fix variable name

* Add isValidURL helper function

* Remove scary RegEx and tidy up code

* add test for using pregenerated urls

* fix: allow rss to be called multiple times

* test: normalize rss feed in test

* chore: add changeset

Co-authored-by: Zade Viggers <74938858+zadeviggers@users.noreply.github.com>
Co-authored-by: zadeviggers <zade.viggers@gmail.com>

6 files changed, 75 insertions, 25 deletions

diff --git a/.changeset/flat-mayflies-ring.md b/.changeset/flat-mayflies-ring.md
new file mode 100644
index 000000000..8cba31592
--- /dev/null
+++ b/.changeset/flat-mayflies-ring.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix bug with RSS feed generation. `rss()` can now be called multiple times and URLs can now be fully qualified.
diff --git a/packages/astro/src/core/build/page-data.ts b/packages/astro/src/core/build/page-data.ts
index 5b3605c24..8a40277f8 100644
--- a/packages/astro/src/core/build/page-data.ts
+++ b/packages/astro/src/core/build/page-data.ts
@@ -78,26 +78,31 @@ export async function collectPagesData(opts: CollectPagesDataOptions): Promise<C
 					debug(logging, 'build', `├── ${colors.bold(colors.red('✗'))} ${route.component}`);
 					throw err;
 				});
-			if (result.rss?.xml) {
-				const { url, content } = result.rss.xml;
-				if (content) {
-					const rssFile = new URL(url.replace(/^\/?/, './'), astroConfig.dist);
-					if (assets[fileURLToPath(rssFile)]) {
-						throw new Error(`[getStaticPaths] RSS feed ${url} already exists.\nUse \`rss(data, {url: '...'})\` to choose a unique, custom URL. (${route.component})`);
+			if (result.rss?.length) {
+				for (let i = 0; i < result.rss.length; i++) {
+					const rss = result.rss[i];
+					if (rss.xml) {
+						const { url, content } = rss.xml;
+						if (content) {
+							const rssFile = new URL(url.replace(/^\/?/, './'), astroConfig.dist);
+							if (assets[fileURLToPath(rssFile)]) {
+								throw new Error(`[getStaticPaths] RSS feed ${url} already exists.\nUse \`rss(data, {url: '...'})\` to choose a unique, custom URL. (${route.component})`);
+							}
+							assets[fileURLToPath(rssFile)] = content;
+						}
 					}
-					assets[fileURLToPath(rssFile)] = content;
+					if (rss.xsl?.content) {
+						const { url, content } = rss.xsl;
+						const stylesheetFile = new URL(url.replace(/^\/?/, './'), astroConfig.dist);
+						if (assets[fileURLToPath(stylesheetFile)]) {
+							throw new Error(
+								`[getStaticPaths] RSS feed stylesheet ${url} already exists.\nUse \`rss(data, {stylesheet: '...'})\` to choose a unique, custom URL. (${route.component})`
+							);
+						}
+						assets[fileURLToPath(stylesheetFile)] = content;
+					}	
 				}
 			}
-			if (result.rss?.xsl?.content) {
-				const { url, content } = result.rss.xsl;
-				const stylesheetFile = new URL(url.replace(/^\/?/, './'), astroConfig.dist);
-				if (assets[fileURLToPath(stylesheetFile)]) {
-					throw new Error(
-						`[getStaticPaths] RSS feed stylesheet ${url} already exists.\nUse \`rss(data, {stylesheet: '...'})\` to choose a unique, custom URL. (${route.component})`
-					);
-				}
-				assets[fileURLToPath(stylesheetFile)] = content;
-			}
 			allPages[route.component] = {
 				route,
 				paths: result.paths,
@@ -119,7 +124,7 @@ export async function collectPagesData(opts: CollectPagesDataOptions): Promise<C
 	return { assets, allPages };
 }
 
-async function getStaticPathsForRoute(opts: CollectPagesDataOptions, route: RouteData): Promise<{ paths: string[]; rss?: RSSResult }> {
+async function getStaticPathsForRoute(opts: CollectPagesDataOptions, route: RouteData): Promise<{ paths: string[]; rss?: RSSResult[] }> {
 	const { astroConfig, logging, routeCache, viteServer } = opts;
 	if (!viteServer) throw new Error(`vite.createServer() not called!`);
 	const filePath = new URL(`./${route.component}`, astroConfig.projectRoot);
diff --git a/packages/astro/src/core/ssr/rss.ts b/packages/astro/src/core/ssr/rss.ts
index a61df7841..269ffbdf4 100644
--- a/packages/astro/src/core/ssr/rss.ts
+++ b/packages/astro/src/core/ssr/rss.ts
@@ -1,7 +1,7 @@
 import type { RSSFunction, RSS, RSSResult, FeedResult, RouteData } from '../../@types/astro';
 
 import { XMLValidator } from 'fast-xml-parser';
-import { canonicalURL, PRETTY_FEED_V3 } from '../util.js';
+import { canonicalURL, isValidURL, PRETTY_FEED_V3 } from '../util.js';
 
 /** Validates getStaticPaths.rss */
 export function validateRSS(args: GenerateRSSArgs): void {
@@ -48,8 +48,10 @@ export function generateRSS(args: GenerateRSSArgs): string {
 		if (!result.title) throw new Error(`[${srcFile}] rss.items required "title" property is missing. got: "${JSON.stringify(result)}"`);
 		if (!result.link) throw new Error(`[${srcFile}] rss.items required "link" property is missing. got: "${JSON.stringify(result)}"`);
 		xml += `<title><![CDATA[${result.title}]]></title>`;
-		xml += `<link>${canonicalURL(result.link, site).href}</link>`;
-		xml += `<guid>${canonicalURL(result.link, site).href}</guid>`;
+		// If the item's link is already a valid URL, don't mess with it.
+		const itemLink = isValidURL(result.link) ? result.link : canonicalURL(result.link, site).href;
+		xml += `<link>${itemLink}</link>`;
+		xml += `<guid>${itemLink}</guid>`;
 		if (result.description) xml += `<description><![CDATA[${result.description}]]></description>`;
 		if (result.pubDate) {
 			// note: this should be a Date, but if user provided a string or number, we can work with that, too.
@@ -81,13 +83,14 @@ export function generateRSSStylesheet() {
 }
 
 /** Generated function to be run  */
-export function generateRssFunction(site: string | undefined, route: RouteData): { generator: RSSFunction; rss?: RSSResult } {
-	let result: RSSResult = {} as any;
+export function generateRssFunction(site: string | undefined, route: RouteData): { generator: RSSFunction; rss?: RSSResult[] } {
+	let results: RSSResult[] = [];
 	return {
 		generator: function rssUtility(args: RSS) {
 			if (!site) {
 				throw new Error(`[${route.component}] rss() tried to generate RSS but "buildOptions.site" missing in astro.config.mjs`);
 			}
+			let result: RSSResult = {} as any;
 			const { dest, ...rssData } = args;
 			const feedURL = dest || '/rss.xml';
 			if (rssData.stylesheet === true) {
@@ -105,7 +108,8 @@ export function generateRssFunction(site: string | undefined, route: RouteData):
 				url: feedURL,
 				content: generateRSS({ rssData, site, srcFile: route.component, feedURL }),
 			};
+			results.push(result);
 		},
-		rss: result,
+		rss: results,
 	};
 }
diff --git a/packages/astro/src/core/util.ts b/packages/astro/src/core/util.ts
index 10ee44c00..9deb72f5e 100644
--- a/packages/astro/src/core/util.ts
+++ b/packages/astro/src/core/util.ts
@@ -15,6 +15,15 @@ export function canonicalURL(url: string, base?: string): URL {
 	return new URL(pathname, base);
 }
 
+/** Check if a URL is already valid */
+export function isValidURL(url: string):boolean {
+	try {
+		new URL(url)
+		return true;
+	} catch (e) {}
+	return false;
+}
+
 /** is a specifier an npm package? */
 export function parseNpmName(spec: string): { scope?: string; name: string; subpath?: string } | undefined {
 	// not an npm package
diff --git a/packages/astro/test/astro-sitemap-rss.test.js b/packages/astro/test/astro-sitemap-rss.test.js
index f3ef8d220..492c144a2 100644
--- a/packages/astro/test/astro-sitemap-rss.test.js
+++ b/packages/astro/test/astro-sitemap-rss.test.js
@@ -25,8 +25,15 @@ describe('Sitemaps', () => {
 ]]></description><pubDate>Tue, 19 Oct 1999 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>259</itunes:duration><itunes:explicit>true</itunes:explicit></item></channel></rss>`
 			);
 		});
+		it('generates RSS with pregenerated URLs correctly', async () => {
+			const rss = await fixture.readFile('/custom/feed-pregenerated-urls.xml');
+			expect(rss).to.equal(
+				`<?xml version="1.0" encoding="UTF-8"?><rss version="2.0" xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" xmlns:content="http://purl.org/rss/1.0/modules/content/"><channel><title><![CDATA[MF Doomcast]]></title><description><![CDATA[The podcast about the things you find on a picnic, or at a picnic table]]></description><link>https://astro.build/custom/feed-pregenerated-urls.xml</link><language>en-us</language><itunes:author>MF Doom</itunes:author><item><title><![CDATA[Rap Snitch Knishes (feat. Mr. Fantastik)]]></title><link>https://example.com/episode/rap-snitch-knishes/</link><guid>https://example.com/episode/rap-snitch-knishes/</guid><description><![CDATA[Complex named this song the “22nd funniest rap song of all time.”]]></description><pubDate>Tue, 16 Nov 2004 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>172</itunes:duration><itunes:explicit>true</itunes:explicit></item><item><title><![CDATA[Fazers]]></title><link>https://example.com/episode/fazers/</link><guid>https://example.com/episode/fazers/</guid><description><![CDATA[Rhapsody ranked Take Me to Your Leader 17th on its list “Hip-Hop’s Best Albums of the Decade”]]></description><pubDate>Thu, 03 Jul 2003 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>197</itunes:duration><itunes:explicit>true</itunes:explicit></item><item><title><![CDATA[Rhymes Like Dimes (feat. Cucumber Slice)]]></title><link>https://example.com/episode/rhymes-like-dimes/</link><guid>https://example.com/episode/rhymes-like-dimes/</guid><description><![CDATA[Operation: Doomsday has been heralded as an underground classic that established MF Doom's rank within the underground hip-hop scene during the early to mid-2000s.
+]]></description><pubDate>Tue, 19 Oct 1999 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>259</itunes:duration><itunes:explicit>true</itunes:explicit></item></channel></rss>`
+			);
+		});
 	});
-
+	
 	describe('Sitemap Generation', () => {
 		it('Generates Sitemap correctly', async () => {
 			let sitemap = await fixture.readFile('/sitemap.xml');
diff --git a/packages/astro/test/fixtures/astro-sitemap-rss/src/pages/episodes/[...page].astro b/packages/astro/test/fixtures/astro-sitemap-rss/src/pages/episodes/[...page].astro
index 5cb25e3de..0c0c676ee 100644
--- a/packages/astro/test/fixtures/astro-sitemap-rss/src/pages/episodes/[...page].astro
+++ b/packages/astro/test/fixtures/astro-sitemap-rss/src/pages/episodes/[...page].astro
@@ -21,6 +21,26 @@ export function getStaticPaths({paginate, rss}) {
     })),
     dest: '/custom/feed.xml',
   });
+  rss({
+    title: 'MF Doomcast',
+    description: 'The podcast about the things you find on a picnic, or at a picnic table',
+    xmlns: {
+      itunes: 'http://www.itunes.com/dtds/podcast-1.0.dtd',
+      content: 'http://purl.org/rss/1.0/modules/content/',
+    },
+    customData: `<language>en-us</language>` +
+      `<itunes:author>MF Doom</itunes:author>`,
+    items: episodes.map((episode) => ({
+      title: episode.title,
+      link: `https://example.com${episode.url}/`,
+      description: episode.description,
+      pubDate: episode.pubDate + 'Z',
+      customData: `<itunes:episodeType>${episode.type}</itunes:episodeType>` +
+        `<itunes:duration>${episode.duration}</itunes:duration>` +
+        `<itunes:explicit>${episode.explicit || false}</itunes:explicit>`,
+    })),
+    dest: '/custom/feed-pregenerated-urls.xml',
+  });
   return paginate(episodes);
 }