allow prerendered pages to link to non-prerenderable endpoints

.changeset/flat-dancers-sell.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Allow prerendered pages to link to non-prerenderable endpoints

packages/kit/src/runtime/server/endpoint.js

@@ -32,7 +32,14 @@ export async function render_endpoint(event, mod, state) {
 	}
 
 	if (state.prerendering && !prerender) {
-		throw new Error(`${event.routeId} is not prerenderable`);
+		if (state.initiator) {
+			// if request came from a prerendered page, bail
+			throw new Error(`${event.routeId} is not prerenderable`);
+		} else {
+			// if request came direct from the crawler, signal that
+			// this route cannot be prerendered, but don't bail
+			return new Response(undefined, { status: 204 });
+		}
 	}
 
 	try {

packages/kit/test/prerendering/options/src/routes/+layout.svelte

@@ -1 +1,5 @@
+<svelte:head>
+	<link rel="alternate" href="/path-base/rss.xml" />
+</svelte:head>
+
 <slot />

packages/kit/test/prerendering/options/src/routes/rss.xml/+server.js

@@ -0,0 +1,3 @@
+export function GET() {
+	return new Response('dynamic');
+}

packages/kit/test/prerendering/options/test/test.js

@@ -37,4 +37,8 @@ test('populates fallback 200.html file', () => {
 	assert.ok(content !== '');
 });
 
+test('does not prerender linked +server.js route', () => {
+	assert.ok(!fs.existsSync(`${build}/rss.xml`));
+});
+
 test.run();