From e3544597bee62a43a0254490532f1f3663703d2d Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Mon, 21 Nov 2022 14:52:18 -0500
Subject: [PATCH] [fix] write redirects for prerendered pages with trailing
 slashes (#7747)

fixes #7725
---
 .changeset/quick-weeks-explode.md |  5 ++++
 packages/adapter-vercel/index.js  | 50 ++++++++++++++++++++-----------
 2 files changed, 38 insertions(+), 17 deletions(-)
 create mode 100644 .changeset/quick-weeks-explode.md

diff --git a/.changeset/quick-weeks-explode.md b/.changeset/quick-weeks-explode.md
new file mode 100644
index 000000000000..c78f3af7df0d
--- /dev/null
+++ b/.changeset/quick-weeks-explode.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+[fix] Write redirects for prerendered pages with trailing slashes
diff --git a/packages/adapter-vercel/index.js b/packages/adapter-vercel/index.js
index fbeaef48f731..2cbd295c784c 100644
--- a/packages/adapter-vercel/index.js
+++ b/packages/adapter-vercel/index.js
@@ -13,9 +13,9 @@ export default function ({ external = [], edge, split } = {}) {
 			const node_version = get_node_version();
 
 			const dir = '.vercel/output';
-
 			const tmp = builder.getBuildDirectory('vercel-tmp');
 
+			builder.rimraf(dir);
 			builder.rimraf(tmp);
 
 			const files = fileURLToPath(new URL('./files', import.meta.url).href);
@@ -25,16 +25,34 @@ export default function ({ external = [], edge, split } = {}) {
 				functions: `${dir}/functions`
 			};
 
-			const prerendered_redirects = Array.from(
-				builder.prerendered.redirects,
-				([src, redirect]) => ({
+			/** @type {any[]} */
+			const prerendered_redirects = [];
+
+			/** @type {Record<string, { path: string }>} */
+			const overrides = {};
+
+			for (const [src, redirect] of builder.prerendered.redirects) {
+				prerendered_redirects.push({
 					src,
 					headers: {
 						Location: redirect.location
 					},
 					status: redirect.status
-				})
-			);
+				});
+			}
+
+			for (const [path, page] of builder.prerendered.pages) {
+				if (path.endsWith('/') && path !== '/') {
+					prerendered_redirects.push(
+						{ src: path, dest: path.slice(0, -1) },
+						{ src: path.slice(0, -1), status: 308, headers: { Location: path } }
+					);
+
+					overrides[page.file] = { path: path.slice(1, -1) };
+				} else {
+					overrides[page.file] = { path: path.slice(1) };
+				}
+			}
 
 			/** @type {any[]} */
 			const routes = [
@@ -164,19 +182,17 @@ export default function ({ external = [], edge, split } = {}) {
 
 			builder.log.minor('Writing routes...');
 
-			/** @type {Record<string, { path: string }>} */
-			const overrides = {};
-			builder.prerendered.pages.forEach((page, src) => {
-				overrides[page.file] = { path: src.slice(1) };
-			});
-
 			write(
 				`${dir}/config.json`,
-				JSON.stringify({
-					version: 3,
-					routes,
-					overrides
-				})
+				JSON.stringify(
+					{
+						version: 3,
+						routes,
+						overrides
+					},
+					null,
+					'  '
+				)
 			);
 		}
 	};