From 3bef32f81c56bc600ca307f1bd40787e23e625a5 Mon Sep 17 00:00:00 2001
From: Martin Trapp <94928215+martrapp@users.noreply.github.com>
Date: Thu, 12 Oct 2023 00:08:44 +0200
Subject: [PATCH] Fix: Retain focus for persisted input elements during view
 transitions (#8813)

* add new e2e test: persist focus on transition

* save and restore focus during swap

---------

Co-authored-by: Nate Moore <natemoo-re@users.noreply.github.com>
---
 .changeset/three-toes-talk.md                 |  5 +++
 .../view-transitions/astro.config.mjs         |  2 +-
 .../src/components/Layout.astro               |  2 +-
 .../src/pages/page-with-persistent-form.astro | 20 +++++++++
 .../view-transitions/src/pages/query.astro    |  3 +-
 packages/astro/e2e/view-transitions.test.js   | 22 +++++++++-
 packages/astro/src/transitions/router.ts      | 43 +++++++++++++++++++
 7 files changed, 93 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/three-toes-talk.md
 create mode 100644 packages/astro/e2e/fixtures/view-transitions/src/pages/page-with-persistent-form.astro

diff --git a/.changeset/three-toes-talk.md b/.changeset/three-toes-talk.md
new file mode 100644
index 000000000000..a6a879ad6554
--- /dev/null
+++ b/.changeset/three-toes-talk.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Save and restore focus for persisted input elements during view transitions
diff --git a/packages/astro/e2e/fixtures/view-transitions/astro.config.mjs b/packages/astro/e2e/fixtures/view-transitions/astro.config.mjs
index 68fdc8e2e1eb..2b22ff9cf3f3 100644
--- a/packages/astro/e2e/fixtures/view-transitions/astro.config.mjs
+++ b/packages/astro/e2e/fixtures/view-transitions/astro.config.mjs
@@ -4,7 +4,7 @@ import nodejs from '@astrojs/node';
 
 // https://astro.build/config
 export default defineConfig({
-	output: 'server',
+	output: 'hybrid',
 	adapter: nodejs({ mode: 'standalone' }),
 	integrations: [react()],
 	redirects: {
diff --git a/packages/astro/e2e/fixtures/view-transitions/src/components/Layout.astro b/packages/astro/e2e/fixtures/view-transitions/src/components/Layout.astro
index ddafb98a993f..7ef7b93f8897 100644
--- a/packages/astro/e2e/fixtures/view-transitions/src/components/Layout.astro
+++ b/packages/astro/e2e/fixtures/view-transitions/src/components/Layout.astro
@@ -18,7 +18,7 @@ const { link } = Astro.props as Props;
 				margin: auto;
 			}	
 		</style>
-		<link rel="stylesheet" href="/style.css">
+		<link rel="stylesheet" href="/styles.css">
 		<ViewTransitions />
 		<DarkMode />
 		<meta name="script-executions" content="0">
diff --git a/packages/astro/e2e/fixtures/view-transitions/src/pages/page-with-persistent-form.astro b/packages/astro/e2e/fixtures/view-transitions/src/pages/page-with-persistent-form.astro
new file mode 100644
index 000000000000..c150726ed191
--- /dev/null
+++ b/packages/astro/e2e/fixtures/view-transitions/src/pages/page-with-persistent-form.astro
@@ -0,0 +1,20 @@
+---
+import Layout from '../components/Layout.astro';
+---
+<Layout>
+	<h2>Form 1</h2>
+	<form transition:persist>
+		<input id="input" type="text" name="name" autocomplete="false"/>
+	</form>
+
+	<script>
+		import {navigate} from "astro:transitions/client"
+		const form = document.querySelector("form");
+		form.addEventListener("submit", (e) => {
+			console.log("submit");
+			e.preventDefault();
+			navigate(`${location.pathname}?name=${input.value}`,{history: "replace"});
+			return false;
+		});
+	</script>
+</Layout>
diff --git a/packages/astro/e2e/fixtures/view-transitions/src/pages/query.astro b/packages/astro/e2e/fixtures/view-transitions/src/pages/query.astro
index 44dd03ce0f22..e9bee1f4407c 100644
--- a/packages/astro/e2e/fixtures/view-transitions/src/pages/query.astro
+++ b/packages/astro/e2e/fixtures/view-transitions/src/pages/query.astro
@@ -1,6 +1,7 @@
 ---
 import Layout from '../components/Layout.astro';
-
+export const prerender = false;
+// this works only with SSR, not with SSG. E2e tests run with output=hybrid or server
 const page = Astro.url.searchParams.get('page') || 1;
 ---
 <Layout>
diff --git a/packages/astro/e2e/view-transitions.test.js b/packages/astro/e2e/view-transitions.test.js
index 559592fbade0..d2c14aabdabc 100644
--- a/packages/astro/e2e/view-transitions.test.js
+++ b/packages/astro/e2e/view-transitions.test.js
@@ -788,7 +788,7 @@ test.describe('View Transitions', () => {
 
 	test('replace history', async ({ page, astro }) => {
 		await page.goto(astro.resolveUrl('/one'));
-		// page six loads the router and automatically uses the router to navigate to page 1
+
 		let p = page.locator('#one');
 		await expect(p, 'should have content').toHaveText('Page 1');
 
@@ -833,4 +833,24 @@ test.describe('View Transitions', () => {
 		p = page.locator('#one');
 		await expect(p, 'should have content').toHaveText('Page 1');
 	});
+
+	test('Keep focus on transition', async ({ page, astro }) => {
+		await page.goto(astro.resolveUrl('/page-with-persistent-form'));
+		let locator = page.locator('h2');
+		await expect(locator, 'should have content').toHaveText('Form 1');
+
+		locator = page.locator('#input');
+		await locator.type('Hello');
+		await expect(locator).toBeFocused();
+		await locator.press('Enter');
+
+		await page.waitForURL(/.*name=Hello/);
+		locator = page.locator('h2');
+		await expect(locator, 'should have content').toHaveText('Form 1');
+		locator = page.locator('#input');
+		await expect(locator).toBeFocused();
+
+		await locator.type(' World');
+		await expect(locator).toHaveValue('Hello World');
+	});
 });
diff --git a/packages/astro/src/transitions/router.ts b/packages/astro/src/transitions/router.ts
index c21392e3aa6f..869ed87af5fa 100644
--- a/packages/astro/src/transitions/router.ts
+++ b/packages/astro/src/transitions/router.ts
@@ -215,6 +215,45 @@ async function updateDOM(
 		return null;
 	};
 
+	type SavedFocus = {
+		activeElement: HTMLElement | null;
+		start?: number | null;
+		end?: number | null;
+	};
+
+	const saveFocus = (): SavedFocus => {
+		const activeElement = document.activeElement as HTMLElement;
+		// The element that currently has the focus is part of a DOM tree
+		// that will survive the transition to the new document.
+		// Save the element and the cursor position
+		if (activeElement?.closest('[data-astro-transition-persist]')) {
+			if (
+				activeElement instanceof HTMLInputElement ||
+				activeElement instanceof HTMLTextAreaElement
+			) {
+				const start = activeElement.selectionStart;
+				const end = activeElement.selectionEnd;
+				return { activeElement, start, end };
+			}
+			return { activeElement };
+		} else {
+			return { activeElement: null };
+		}
+	};
+
+	const restoreFocus = ({ activeElement, start, end }: SavedFocus) => {
+		if (activeElement) {
+			activeElement.focus();
+			if (
+				activeElement instanceof HTMLInputElement ||
+				activeElement instanceof HTMLTextAreaElement
+			) {
+				activeElement.selectionStart = start!;
+				activeElement.selectionEnd = end!;
+			}
+		}
+	};
+
 	const swap = () => {
 		// swap attributes of the html element
 		// - delete all attributes from the current document
@@ -263,6 +302,8 @@ async function updateDOM(
 		// Persist elements in the existing body
 		const oldBody = document.body;
 
+		const savedFocus = saveFocus();
+
 		// this will reset scroll Position
 		document.body.replaceWith(newDocument.body);
 		for (const el of oldBody.querySelectorAll(`[${PERSIST_ATTR}]`)) {
@@ -275,6 +316,8 @@ async function updateDOM(
 			}
 		}
 
+		restoreFocus(savedFocus);
+
 		if (popState) {
 			scrollTo(popState.scrollX, popState.scrollY); // usings 'auto' scrollBehavior
 		} else {