fix: construct correct pathname for isr from route with nested params

.changeset/heavy-news-argue.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+fix: construct correct pathname for isr from route with nested params

packages/adapter-vercel/files/serverless.js

@@ -22,10 +22,12 @@ export default async (req, res) => {
 		const [path, search] = req.url.split('?');
 
 		const params = new URLSearchParams(search);
-		const pathname = params.get('__pathname');
+		let pathname = params.get('__pathname');
 
 		if (pathname) {
 			params.delete('__pathname');
+			// Optional routes' pathname replacements look like `/foo/$1/bar` which means we could end up with an url like /foo//bar
+			pathname = pathname.replace(/\/+/g, '/');
 			req.url = `${pathname}${path.endsWith(DATA_SUFFIX) ? DATA_SUFFIX : ''}?${params}`;
 		}
 	}

packages/adapter-vercel/index.js

@@ -3,6 +3,7 @@ import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { nodeFileTrace } from '@vercel/nft';
 import esbuild from 'esbuild';
+import { get_pathname } from './utils.js';
 
 const VALID_RUNTIMES = ['edge', 'nodejs16.x', 'nodejs18.x'];
 
@@ -292,13 +293,7 @@ const plugin = function (defaults = {}) {
 					fs.symlinkSync(relative, `${base}.func`);
 					fs.symlinkSync(`../${relative}`, `${base}/__data.json.func`);
 
-					let i = 1;
-					const pathname = route.segments
-						.map((segment) => {
-							return segment.dynamic ? `$${i++}` : segment.content;
-						})
-						.join('/');
-
+					const pathname = get_pathname(route);
 					const json = JSON.stringify(isr, null, '\t');
 
 					write(`${base}.prerender-config.json`, json);

packages/adapter-vercel/package.json

@@ -21,12 +21,14 @@
 	"files": [
 		"files",
 		"index.js",
+		"utils.js",
 		"index.d.ts"
 	],
 	"scripts": {
 		"lint": "prettier --check . --config ../../.prettierrc --ignore-path .gitignore",
 		"format": "pnpm lint --write",
-		"check": "tsc"
+		"check": "tsc",
+		"test": "uvu test .spec.js"
 	},
 	"dependencies": {
 		"@vercel/nft": "^0.22.1",
@@ -35,7 +37,8 @@
 	"devDependencies": {
 		"@sveltejs/kit": "workspace:^",
 		"@types/node": "^16.18.6",
-		"typescript": "^4.9.4"
+		"typescript": "^4.9.4",
+		"uvu": "^0.5.6"
 	},
 	"peerDependencies": {
 		"@sveltejs/kit": "^1.5.0"

packages/adapter-vercel/test/utils.spec.js

@@ -0,0 +1,38 @@
+import { test } from 'uvu';
+import * as assert from 'uvu/assert';
+import { get_pathname } from '../utils.js';
+
+/**
+ * @param {import('@sveltejs/kit').RouteDefinition<any>['segments']} segments
+ * @param {string} expected
+ */
+function run_get_pathname_test(segments, expected) {
+	const route = /** @type {import('@sveltejs/kit').RouteDefinition<any>} */ ({ segments });
+	assert.equal(get_pathname(route), expected);
+}
+
+test('get_pathname for simple route', () => {
+	run_get_pathname_test([{ content: 'foo', dynamic: false, rest: false }], 'foo');
+});
+
+test('get_pathname for route with parameters', () => {
+	run_get_pathname_test(
+		[
+			{ content: 'foo', dynamic: false, rest: false },
+			{ content: '[bar]', dynamic: true, rest: false }
+		],
+		'foo/$1'
+	);
+});
+
+test('get_pathname for route with parameters within segment', () => {
+	run_get_pathname_test(
+		[
+			{ content: 'foo-[bar]', dynamic: true, rest: false },
+			{ content: '[baz]-buz', dynamic: true, rest: false }
+		],
+		'foo-$1/$2-buz'
+	);
+});
+
+test.run();

packages/adapter-vercel/utils.js

@@ -0,0 +1,23 @@
+/** @param {import("@sveltejs/kit").RouteDefinition<any>} route */
+export function get_pathname(route) {
+	let i = 1;
+
+	return route.segments
+		.map((segment) => {
+			if (!segment.dynamic) {
+				return segment.content;
+			}
+
+			const parts = segment.content.split(/\[(.+?)\](?!\])/);
+			return parts
+				.map((content, j) => {
+					if (j % 2) {
+						return `$${i++}`;
+					} else {
+						return content;
+					}
+				})
+				.join('');
+		})
+		.join('/');
+}