[fix] Silently skip prefetching external URLs instead of warning (#6518)

Fix #6463 by automatically skipping prefetching of external URLs instead of warning app developers.

.changeset/nice-poets-taste.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Silently skip prefetching of external URLs when using `data-sveltekit-prefetch`. Warn like before when calling `prefetch()` for external URLs.

packages/kit/src/runtime/client/client.js

@@ -943,7 +943,7 @@ export function create_client({ target, base, trailing_slash }) {
 
 	/** @param {URL} url */
 	function get_navigation_intent(url) {
-		if (url.origin !== location.origin || !url.pathname.startsWith(base)) return;
+		if (is_external_url(url)) return;
 
 		const path = decodeURI(url.pathname.slice(base.length) || '/');
 
@@ -962,6 +962,11 @@ export function create_client({ target, base, trailing_slash }) {
 		}
 	}
 
+	/** @param {URL} url */
+	function is_external_url(url) {
+		return url.origin !== location.origin || !url.pathname.startsWith(base);
+	}
+
 	/**
 	 * @param {{
 	 *   url: URL;
@@ -1156,6 +1161,7 @@ export function create_client({ target, base, trailing_slash }) {
 			const trigger_prefetch = (event) => {
 				const { url, options } = find_anchor(event);
 				if (url && options.prefetch === '') {
+					if (is_external_url(url)) return;
 					prefetch(url);
 				}
 			};