fix: add link rel=preload for exported sites

package.json

@@ -19,6 +19,7 @@
   },
   "dependencies": {
     "html-minifier": "^3.5.21",
+    "http-link-header": "^1.0.2",
     "shimport": "0.0.14",
     "source-map-support": "^0.5.10",
     "sourcemap-codec": "^1.4.4",

src/api/export.ts

@@ -9,6 +9,7 @@ import clean_html from './utils/clean_html';
 import minify_html from './utils/minify_html';
 import Deferred from './utils/Deferred';
 import { noop } from './utils/noop';
+import { parse as parseLinkHeader } from 'http-link-header';
 
 type Opts = {
 	build_dir?: string,
@@ -21,6 +22,12 @@ type Opts = {
 	onfile?: ({ file, size, status }: { file: string, size: number, status: number }) => void;
 };
 
+type Ref = {
+	uri: string,
+	rel: string,
+	as: string
+};
+
 function resolve(from: string, to: string) {
 	return url.parse(url.resolve(from, to));
 }
@@ -139,38 +146,49 @@ async function _export({
 		clearTimeout(the_timeout); // prevent it hanging at the end
 
 		let type = r.headers.get('Content-Type');
+
 		let body = await r.text();
 
 		const range = ~~(r.status / 100);
 
 		if (range === 2) {
-			if (type === 'text/html' && pathname !== '/service-worker-index.html') {
-				const cleaned = clean_html(body);
+			if (type === 'text/html') {
+				// parse link rel=preload headers and embed them in the HTML
+				let link = parseLinkHeader(r.headers.get('Link') || '');
+				link.refs.forEach((ref: Ref) => {
+					if (ref.rel === 'preload') {
+						body = body.replace('</head>',
+							`<link rel="preload" as=${JSON.stringify(ref.as)} href=${JSON.stringify(ref.uri)}></head>`)
+					}
+				});
+				if (pathname !== '/service-worker-index.html') {
+					const cleaned = clean_html(body);
 
-				const q = yootils.queue(8);
-				let promise;
+					const q = yootils.queue(8);
+					let promise;
 
-				const base_match = /<base ([\s\S]+?)>/m.exec(cleaned);
-				const base_href = base_match && get_href(base_match[1]);
-				const base = resolve(url.href, base_href);
+					const base_match = /<base ([\s\S]+?)>/m.exec(cleaned);
+					const base_href = base_match && get_href(base_match[1]);
+					const base = resolve(url.href, base_href);
 
-				let match;
-				let pattern = /<a ([\s\S]+?)>/gm;
+					let match;
+					let pattern = /<a ([\s\S]+?)>/gm;
 
-				while (match = pattern.exec(cleaned)) {
-					const attrs = match[1];
-					const href = get_href(attrs);
+					while (match = pattern.exec(cleaned)) {
+						const attrs = match[1];
+						const href = get_href(attrs);
 
-					if (href) {
-						const url = resolve(base.href, href);
+						if (href) {
+							const url = resolve(base.href, href);
 
-						if (url.protocol === protocol && url.host === host) {
-							promise = q.add(() => handle(url));
+							if (url.protocol === protocol && url.host === host) {
+								promise = q.add(() => handle(url));
+							}
 						}
 					}
-				}
 
-				await promise;
+					await promise;
+				}
 			}
 		}
 

test/apps/export-webpack/src/client.js

@@ -0,0 +1,9 @@
+import * as sapper from '@sapper/app';
+
+window.start = () => sapper.start({
+	target: document.querySelector('#sapper')
+});
+
+window.prefetchRoutes = () => sapper.prefetchRoutes();
+window.prefetch = href => sapper.prefetch(href);
+window.goto = href => sapper.goto(href);

test/apps/export-webpack/src/routes/_error.svelte

@@ -0,0 +1,3 @@
+<h1>{status}</h1>
+
+<p>{error.message}</p>

test/apps/export-webpack/src/routes/blog/[slug].html

@@ -0,0 +1,13 @@
+<script context="module">
+	export function preload({ params }) {
+		return this.fetch(`blog/${params.slug}.json`).then(r => r.json()).then(post => {
+			return { post };
+		});
+	}
+</script>
+
+<script>
+	export let post;
+</script>
+
+<h1>{post.title}</h1>

test/apps/export-webpack/src/routes/blog/[slug].json.js

@@ -0,0 +1,19 @@
+import posts from './_posts.js';
+
+export function get(req, res) {
+	const post = posts.find(post => post.slug === req.params.slug);
+
+	if (post) {
+		res.writeHead(200, {
+			'Content-Type': 'application/json'
+		});
+
+		res.end(JSON.stringify(post));
+	} else {
+		res.writeHead(404, {
+			'Content-Type': 'application/json'
+		});
+
+		res.end(JSON.stringify({ message: 'not found' }));
+	}
+}

test/apps/export-webpack/src/routes/blog/_posts.js

@@ -0,0 +1,5 @@
+export default [
+	{ slug: 'foo', title: 'once upon a foo' },
+	{ slug: 'bar', title: 'a bar is born' },
+	{ slug: 'baz', title: 'bazzily ever after' }
+];

test/apps/export-webpack/src/routes/blog/index.html

@@ -0,0 +1,17 @@
+<script context="module">
+	export function preload() {
+		return this.fetch('blog.json').then(r => r.json()).then(posts => {
+			return { posts };
+		});
+	}
+</script>
+
+<script>
+	export let posts;
+</script>
+
+<h1>blog</h1>
+
+{#each posts as post}
+	<p><a href="blog/{post.slug}">{post.title}</a></p>
+{/each}

test/apps/export-webpack/src/routes/blog/index.json.js

@@ -0,0 +1,9 @@
+import posts from './_posts.js';
+
+export function get(req, res) {
+	res.writeHead(200, {
+		'Content-Type': 'application/json'
+	});
+
+	res.end(JSON.stringify(posts));
+}

test/apps/export-webpack/src/routes/index.svelte

@@ -0,0 +1,4 @@
+<h1>Great success!</h1>
+
+<a href="blog">blog</a>
+<a href="">empty anchor</a>

test/apps/export-webpack/src/server.js

@@ -0,0 +1,15 @@
+import sirv from 'sirv';
+import polka from 'polka';
+import * as sapper from '@sapper/server';
+
+const { PORT, NODE_ENV } = process.env;
+const dev = NODE_ENV === 'development';
+
+polka()
+	.use(
+		sirv('static', { dev }),
+		sapper.middleware()
+	)
+	.listen(PORT, err => {
+		if (err) console.log('error', err);
+	});