Vt follow redirects (#8522)

* View Transitions redirects WIP

* transition across redirects

* added changeset

---------

Co-authored-by: Matthew Phillips <matthew@skypack.dev>

5 files changed, 78 insertions, 6 deletions

diff --git a/.changeset/warm-windows-occur.md b/.changeset/warm-windows-occur.md
new file mode 100644
index 000000000..47c797f2f
--- /dev/null
+++ b/.changeset/warm-windows-occur.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+let view transitions handle same origin redirects
diff --git a/packages/astro/components/ViewTransitions.astro b/packages/astro/components/ViewTransitions.astro
index 6ae8f3592..77d56e652 100644
--- a/packages/astro/components/ViewTransitions.astro
+++ b/packages/astro/components/ViewTransitions.astro
@@ -65,9 +65,19 @@ const { fallback = 'animate' } = Astro.props as Props;
 	};
 
 	async function getHTML(href: string) {
-		const res = await fetch(href);
+		let res;
+		try {
+			res = await fetch(href);
+		} catch (err) {
+			return { ok: false };
+		}
 		const html = await res.text();
-		return { ok: res.ok, html };
+		return {
+			ok: res.ok,
+			html,
+			redirected: res.redirected ? res.url : undefined,
+			contentType: res.headers.get('content-type'),
+		};
 	}
 
 	function getFallback(): Fallback {
@@ -280,13 +290,16 @@ const { fallback = 'animate' } = Astro.props as Props;
 	async function navigate(dir: Direction, loc: URL, state?: State) {
 		let finished: Promise<void>;
 		const href = loc.href;
-		const { html, ok } = await getHTML(href);
+		const { html, ok, contentType, redirected } = await getHTML(href);
+		// if there was a redirection, show the final URL in the browser's address bar
+		redirected && (loc = new URL(redirected));
 		// If there is a problem fetching the new page, just do an MPA navigation to it.
-		if (!ok) {
+		if (!ok || contentType !== 'text/html') {
 			location.href = href;
 			return;
 		}
-		const doc = parser.parseFromString(html, 'text/html');
+
+		const doc = parser.parseFromString(html, contentType);
 		if (!doc.querySelector('[name="astro-view-transitions-enabled"]')) {
 			location.href = href;
 			return;
diff --git a/packages/astro/e2e/fixtures/view-transitions/astro.config.mjs b/packages/astro/e2e/fixtures/view-transitions/astro.config.mjs
index 02dc2043d..68fdc8e2e 100644
--- a/packages/astro/e2e/fixtures/view-transitions/astro.config.mjs
+++ b/packages/astro/e2e/fixtures/view-transitions/astro.config.mjs
@@ -7,6 +7,10 @@ export default defineConfig({
 	output: 'server',
 	adapter: nodejs({ mode: 'standalone' }),
 	integrations: [react()],
+	redirects: {
+		'/redirect-two': '/two',
+		'/redirect-external': 'http://example.com/',
+	},
 	vite: {
 		build: {
 			assetsInlineLimit: 0,
diff --git a/packages/astro/e2e/fixtures/view-transitions/src/pages/one.astro b/packages/astro/e2e/fixtures/view-transitions/src/pages/one.astro
index 3f9666c1d..cc57e76d8 100644
--- a/packages/astro/e2e/fixtures/view-transitions/src/pages/one.astro
+++ b/packages/astro/e2e/fixtures/view-transitions/src/pages/one.astro
@@ -8,6 +8,8 @@ import Layout from '../components/Layout.astro';
 	<a id="click-three" href="/three">go to 3</a>
 	<a id="click-longpage" href="/long-page">go to long page</a>
 	<a id="click-self" href="">go to top</a>
+	<a id="click-redirect-two" href="/redirect-two">go to redirect 2</a>
+	<a id="click-redirect-external" href="/redirect-external">go to a redirect external</a>
 
 	<div id="test">test content</div>
 </Layout>
diff --git a/packages/astro/e2e/view-transitions.test.js b/packages/astro/e2e/view-transitions.test.js
index 6421b5fc3..f1c1c4ef8 100644
--- a/packages/astro/e2e/view-transitions.test.js
+++ b/packages/astro/e2e/view-transitions.test.js
@@ -566,7 +566,55 @@ test.describe('View Transitions', () => {
 		await expect(p, 'should have content').toHaveText('Page 1');
 	});
 
-	test('client:only styles are retained on transition', async ({ page, astro }) => {
+	test('Moving to a page which redirects to another', async ({ page, astro }) => {
+		const loads = [];
+		page.addListener('load', (p) => {
+			loads.push(p.title());
+		});
+
+		// Go to page 1
+		await page.goto(astro.resolveUrl('/one'));
+		let p = page.locator('#one');
+		await expect(p, 'should have content').toHaveText('Page 1');
+
+		// go to page 2
+		await page.click('#click-redirect-two');
+		p = page.locator('#two');
+		await expect(p, 'should have content').toHaveText('Page 2');
+
+		// go back
+		await page.goBack();
+		p = page.locator('#one');
+		await expect(p, 'should have content').toHaveText('Page 1');
+
+		expect(
+			loads.length,
+			'There should only be the initial page load and two normal transitions'
+		).toEqual(1);
+	});
+
+	test('Redirect to external site causes page load', async ({ page, astro }) => {
+		const loads = [];
+		page.addListener('load', (p) => {
+			loads.push(p.title());
+		});
+
+		// Go to page 1
+		await page.goto(astro.resolveUrl('/one'));
+		let p = page.locator('#one');
+		await expect(p, 'should have content').toHaveText('Page 1');
+
+		// go to external page
+		await page.click('#click-redirect-external');
+		// doesn't work for playwright when we are too fast
+		await page.waitForTimeout(1000);
+		p = page.locator('h1');
+		await expect(p, 'should have content').toBeVisible();
+
+		expect(loads.length, 'There should be 2 page loads').toEqual(2);
+	});
+
+  test('client:only styles are retained on transition', async ({ page, astro }) => {
 		const totalExpectedStyles = 8;
 
 		// Go to page 1