feat: use config.kit.paths.base for static assets

fixes #4442, fixes #2843

- add manifest.prefix and builder.getAppPrefixDirectory()
- adapter-cloudflare*: use manifest.prefix instead of manifest.appDir
- adapter-netlify: use prefixed appDir for cache headers
- adapter-vercel: use prefixed appDir for routes.json
- adapter-cloudflare, adapter-cloudflare-workers, adapter-netlify: write static assets to "$dest/$base"

Author: hmnd

.changeset/smooth-waves-accept.md

@@ -0,0 +1,9 @@
+---
+'@sveltejs/adapter-cloudflare': patch
+'@sveltejs/adapter-cloudflare-workers': patch
+'@sveltejs/adapter-netlify': patch
+'@sveltejs/adapter-vercel': patch
+'@sveltejs/kit': patch
+---
+
+Use config.kit.paths.base prefix for static assets

packages/adapter-cloudflare-workers/files/entry.js

@@ -6,7 +6,7 @@ const static_asset_manifest = JSON.parse(static_asset_manifest_json);
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/`;
+const { prefix } = manifest;
 
 export default {
 	/**

packages/adapter-cloudflare-workers/index.js

@@ -73,8 +73,9 @@ export default function () {
 			});
 
 			builder.log.minor('Copying assets...');
-			builder.writeClient(site.bucket);
-			builder.writePrerendered(site.bucket);
+			const prefixedBucket = `${site.bucket}${builder.config.kit.paths.base}`;
+			builder.writeClient(prefixedBucket);
+			builder.writePrerendered(prefixedBucket);
 		}
 	};
 }

packages/adapter-cloudflare/index.js

@@ -23,8 +23,9 @@ export default function () {
 			builder.rimraf(tmp);
 			builder.mkdirp(tmp);
 
-			builder.writeClient(dest);
-			builder.writePrerendered(dest);
+			const prefixedDest = `${dest}${builder.config.kit.paths.base}`;
+			builder.writeClient(prefixedDest);
+			builder.writePrerendered(prefixedDest);
 
 			const relativePath = posix.relative(tmp, builder.getServerDirectory());
 

packages/adapter-cloudflare/src/worker.js

@@ -4,7 +4,7 @@ import * as Cache from 'worktop/cfw.cache';
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/`;
+const { prefix } = manifest;
 
 /** @type {import('worktop/cfw').Module.Worker<{ ASSETS: import('worktop/cfw.durable').Durable.Object }>} */
 const worker = {

packages/adapter-netlify/index.js

@@ -55,15 +55,17 @@ export default function ({ split = false, edge = edge_set_in_env_var } = {}) {
 			builder.log.minor(`Publishing to "${publish}"`);
 
 			builder.log.minor('Copying assets...');
-			builder.writeClient(publish);
-			builder.writePrerendered(publish);
+
+			const prefixedPublish = `${publish}${builder.config.kit.paths.base}`;
+			builder.writeClient(prefixedPublish);
+			builder.writePrerendered(prefixedPublish);
 
 			builder.log.minor('Writing custom headers...');
 			const headers_file = join(publish, '_headers');
 			builder.copy('_headers', headers_file);
 			appendFileSync(
 				headers_file,
-				`\n\n/${builder.config.kit.appDir}/immutable/*\n  cache-control: public\n  cache-control: immutable\n  cache-control: max-age=31536000\n`
+				`\n\n/${builder.getPrefixedAppDirectory()}/immutable/*\n  cache-control: public\n  cache-control: immutable\n  cache-control: max-age=31536000\n`
 			);
 
 			// for esbuild, use ESM

packages/adapter-vercel/index.js

@@ -118,7 +118,7 @@ export default function ({ external = [], edge, split } = {}) {
 				...redirects[builder.config.kit.trailingSlash],
 				...prerendered_redirects,
 				{
-					src: `/${builder.config.kit.appDir}/.+`,
+					src: `/${builder.getPrefixedAppDirectory()}/.+`,
 					headers: {
 						'cache-control': 'public, immutable, max-age=31536000'
 					}

packages/kit/src/core/adapt/builder.js

@@ -121,6 +121,10 @@ export function create_builder({ config, build_data, prerendered, log }) {
 			return config.kit.files.assets;
 		},
 
+		getPrefixedAppDirectory() {
+			return build_data.prefix;
+		},
+
 		writeClient(dest) {
 			return [...copy(`${config.kit.outDir}/output/client`, dest)];
 		},

packages/kit/src/core/build/index.js

@@ -65,6 +65,7 @@ export function generate_manifest({ build_data, relative_path, routes, format =
 	// prettier-ignore
 	return `{
 		appDir: ${s(build_data.app_dir)},
+		prefix: ${s(build_data.prefix)},
 		assets: new Set(${s(assets)}),
 		mimeTypes: ${s(get_mime_lookup(build_data.manifest_data))},
 		_: {

packages/kit/src/core/dev/plugin.js

@@ -44,6 +44,7 @@ export async function dev(vite, vite_config, svelte_config) {
 
 		manifest = {
 			appDir: svelte_config.kit.appDir,
+			prefix: svelte_config.kit.appDir,
 			assets: new Set(manifest_data.assets.map((asset) => asset.file)),
 			mimeTypes: get_mime_lookup(manifest_data),
 			_: {

packages/kit/src/core/generate_manifest/index.js

@@ -286,6 +286,7 @@ function kit() {
 			log.info(`Client build completed. Wrote ${chunks.length} chunks and ${assets.length} assets`);
 
 			log.info('Building server');
+			const assets_prefix = `${svelte_config.kit.paths.assets || svelte_config.kit.paths.base}/${svelte_config.kit.appDir}/`;
 			const options = {
 				cwd,
 				config: svelte_config,
@@ -301,6 +302,7 @@ function kit() {
 			/** @type {import('types').BuildData} */
 			build_data = {
 				app_dir: svelte_config.kit.appDir,
+				prefix: assets_prefix,
 				manifest_data,
 				service_worker: options.service_worker_entry_file ? 'service-worker.js' : null, // TODO make file configurable?
 				client,

packages/kit/src/vite/dev/index.js

@@ -45,6 +45,7 @@ export interface Builder {
 	getClientDirectory(): string;
 	getServerDirectory(): string;
 	getStaticDirectory(): string;
+	getPrefixedAppDirectory(): string;
 
 	/**
 	 * @param dest the destination folder to which files should be copied
@@ -273,6 +274,7 @@ export class Server {
 
 export interface SSRManifest {
 	appDir: string;
+	prefix: string;
 	assets: Set<string>;
 	mimeTypes: Record<string, string>;
 

packages/kit/src/vite/index.js

@@ -44,6 +44,7 @@ export interface Asset {
 
 export interface BuildData {
 	app_dir: string;
+	prefix: string;
 	manifest_data: ManifestData;
 	service_worker: string | null;
 	client: {