prerender external links

.changeset/tall-berries-guess.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+[breaking] Crawl rel="external" links when prerendering

documentation/docs/07-a-options.md

@@ -43,3 +43,5 @@ Adding a `rel=external` attribute to a link...
 ```
 
 ...will trigger a browser navigation when the link is clicked.
+
+> SvelteKit does not exclude root-relative external links from prerendering, which will cause 404s if these URLs are intended to be served by a separate app. Use a custom [`prerender.onError`](/docs/configuration#prerender) handler if you need to ignore them.

packages/kit/src/core/adapt/prerender/crawl.js

@@ -8,8 +8,6 @@ const TAG_OPEN = /[a-zA-Z]/;
 const TAG_CHAR = /[a-zA-Z0-9]/;
 const ATTRIBUTE_NAME = /[^\t\n\f />"'=]/;
 
-const EXTERNAL = /\bexternal\b/;
-
 const WHITESPACE = /[\s\n\r]/;
 
 /** @param {string} html */
@@ -88,7 +86,6 @@ export function crawl(html) {
 					}
 				}
 
-				let rel = '';
 				let href = '';
 
 				while (i < html.length) {
@@ -149,9 +146,7 @@ export function crawl(html) {
 								i -= 1;
 							}
 
-							if (name === 'rel') {
-								rel = value;
-							} else if (name === 'href') {
+							if (name === 'href') {
 								href = value;
 							} else if (name === 'src') {
 								hrefs.push(value);
@@ -183,7 +178,7 @@ export function crawl(html) {
 					i += 1;
 				}
 
-				if (href && !EXTERNAL.test(rel)) {
+				if (href) {
 					hrefs.push(href);
 				}
 			}

packages/kit/src/core/adapt/prerender/fixtures/include-rel-external/output.json

@@ -0,0 +1 @@
+["/styles.css", "/favicon.png", "https://external.com", "/wheee"]