feat: fetchable dev environments

.changeset/rich-wombats-flash.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': major
+---
+
+breaking: remove `adapter.emulate`

.changeset/short-chefs-stare.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': major
+---
+
+feat: use the Vite Environment API in development, preview, build analysis and prerendering

documentation/docs/25-build-and-deploy/99-writing-adapters.md

@@ -21,14 +21,6 @@ export default function (options) {
 		async adapt(builder) {
 			// adapter implementation
 		},
-		async emulate() {
-			return {
-				async platform({ config, prerender }) {
-					// the returned object becomes `event.platform` during dev, build and
-					// preview. Its shape is that of `App.Platform`
-				}
-			}
-		},
 		supports: {
 			read: ({ config, route }) => {
 				// Return `true` if the route with the given `config` can use `read`
@@ -39,14 +31,19 @@ export default function (options) {
 				// Return `true` if this adapter supports loading `instrumentation.server.js`.
 				// Return `false if it can't, or throw a descriptive error.
 			}
+		},
+		vite: {
+			plugins: [
+				// add plugins here to integrate with Vite
+			]
 		}
 	};
 
 	return adapter;
 }
 ```
 
-Of these, `name` and `adapt` are required. `emulate` and `supports` are optional.
+Of these, `name` and `adapt` are required. `vite.plugins` and `supports` are optional.
 
 Within the `adapt` method, there are a number of things that an adapter should do:
 
@@ -61,3 +58,44 @@ Within the `adapt` method, there are a number of things that an adapter should d
 - Put the user's static files and the generated JS/CSS in the correct location for the target platform
 
 Where possible, we recommend putting the adapter output under the `build/` directory with any intermediate output placed under `.svelte-kit/[adapter-name]`.
+
+## Configuring the development and preview experience
+
+By default, SvelteKit runs your server code through a Node.js runtime when running `vite dev` and `vite preview`. You can change this behaviour by adding a Vite plugin that has a `configureServer` and `configurePreviewServer` hook to route requests to [a different runtime](https://vite.dev/guide/api-environment-runtimes).
+
+The main Vite server environment SvelteKit uses is named `ssr`. You can change its settings by referencing it in the `config` hook of a Vite plugin.
+
+```js
+// @errors: 2304 1005 1109
+config(userConfig) {
+	userConfig.environments.ssr = { ... }
+}
+```
+
+You can also create your own server entry file by importing the `Server` class from `sveltekit:server`, the environment variables loaded by Vite through `env` from `sveltekit:env`, and your app-specific information as `manifest` from `sveltekit:server-manifest`.
+
+```js
+import { env } from 'sveltekit:env';
+import { Server } from 'sveltekit:server';
+import { manifest } from 'sveltekit:server-manifest';
+
+const server = new Server(manifest);
+
+await server.init({ env });
+
+export default {
+	/**
+	 * @param {Request} request
+	 * @returns {Promise<Response>}
+	 */
+	async fetch(request) {
+		return await server.respond(request, {
+			getClientAddress: () => {
+				return request.headers.get('how-your-platform-exposes-the-remote-address')
+			}
+		});
+	}
+}
+
+import.meta.hot?.accept();
+```

packages/adapter-cloudflare/index.js

@@ -2,7 +2,7 @@ import { copyFileSync, existsSync, readFileSync, writeFileSync } from 'node:fs';
 import path from 'node:path';
 import process from 'node:process';
 import { fileURLToPath } from 'node:url';
-import { getPlatformProxy, unstable_readConfig } from 'wrangler';
+import { unstable_readConfig } from 'wrangler';
 import {
 	is_building_for_cloudflare_pages,
 	validate_worker_settings,
@@ -175,41 +175,6 @@ export default function (options = {}) {
 				writeFileSync(`${dest}/.assetsignore`, generate_assetsignore(), { flag: 'a' });
 			}
 		},
-		emulate() {
-			// we want to invoke `getPlatformProxy` only once, but await it only when it is accessed.
-			// If we would await it here, it would hang indefinitely because the platform proxy only resolves once a request happens
-			const get_emulated = async () => {
-				const proxy = await getPlatformProxy(options.platformProxy);
-				const platform = /** @type {App.Platform} */ ({
-					env: proxy.env,
-					ctx: proxy.ctx,
-					context: proxy.ctx, // deprecated in favor of ctx
-					caches: proxy.caches,
-					cf: proxy.cf
-				});
-				/** @type {Record<string, any>} */
-				const env = {};
-				const prerender_platform = /** @type {App.Platform} */ (/** @type {unknown} */ ({ env }));
-				for (const key in proxy.env) {
-					Object.defineProperty(env, key, {
-						get: () => {
-							throw new Error(`Cannot access platform.env.${key} in a prerenderable route`);
-						}
-					});
-				}
-				return { platform, prerender_platform };
-			};
-
-			/** @type {{ platform: App.Platform, prerender_platform: App.Platform }} */
-			let emulated;
-
-			return {
-				platform: async ({ prerender }) => {
-					emulated ??= await get_emulated();
-					return prerender ? emulated.prerender_platform : emulated.platform;
-				}
-			};
-		},
 		supports: {
 			read: () => true,
 			instrumentation: () => true

packages/adapter-cloudflare/test/apps/workers/test/test.js

@@ -7,7 +7,8 @@ test('worker', async ({ page }) => {
 	await expect(page.locator('h1')).toContainText('Sum: 3');
 });
 
-test('ctx', async ({ request }) => {
+// TODO: re-enable once we add the vite cloudflare plugin
+test.skip('ctx', async ({ request }) => {
 	const res = await request.get('/ctx');
 	expect(await res.text()).toBe('ctx works');
 });

packages/adapter-static/test/apps/prerendered/package.json

@@ -1,5 +1,5 @@
 {
-	"name": "~TODO~",
+	"name": "test-static-prerendered",
 	"version": "0.0.1",
 	"private": true,
 	"scripts": {

packages/adapter-static/test/apps/spa/package.json

@@ -1,5 +1,5 @@
 {
-	"name": "~TODO~",
+	"name": "test-static-spa",
 	"version": "0.0.1",
 	"private": true,
 	"scripts": {

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

@@ -7,7 +7,7 @@ import { extname, resolve, join, dirname, relative } from 'node:path';
 import { pipeline } from 'node:stream';
 import { promisify, styleText } from 'node:util';
 import zlib from 'node:zlib';
-import { copy, rimraf, mkdirp, posixify } from '../../utils/filesystem.js';
+import { copy, rimraf, mkdirp } from '../../utils/filesystem.js';
 import { generate_manifest } from '../generate_manifest/index.js';
 import { get_route_segments } from '../../utils/routing.js';
 import { get_env } from '../../exports/vite/utils.js';
@@ -16,6 +16,7 @@ import { write } from '../sync/utils.js';
 import { list_files } from '../utils.js';
 import { find_server_assets } from '../generate_manifest/find_server_assets.js';
 import { reserved } from '../env.js';
+import { posixify } from '../../utils/os.js';
 
 const pipe = promisify(pipeline);
 const extensions = ['.html', '.js', '.mjs', '.json', '.css', '.svg', '.xml', '.wasm', '.txt'];
@@ -31,7 +32,8 @@ const extensions = ['.html', '.js', '.mjs', '.json', '.css', '.svg', '.xml', '.w
  *   prerender_map: PrerenderMap;
  *   log: Logger;
  *   vite_config: ResolvedConfig;
- *   remotes: RemoteChunk[]
+ *   remotes: RemoteChunk[];
+ *   out: string;
  * }} opts
  * @returns {Builder}
  */
@@ -44,7 +46,8 @@ export function create_builder({
 	prerender_map,
 	log,
 	vite_config,
-	remotes
+	remotes,
+	out
 }) {
 	/** @type {Map<RouteDefinition, RouteData>} */
 	const lookup = new Map();
@@ -113,11 +116,10 @@ export function create_builder({
 
 		async generateFallback(dest) {
 			const manifest_path = `${config.kit.outDir}/output/server/manifest-full.js`;
-			const env = get_env(config.kit.env, vite_config.mode);
 
 			const fallback = await generate_fallback({
 				manifest_path,
-				env: { ...env.private, ...env.public },
+				out,
 				root: vite_config.root
 			});
 

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

@@ -3,7 +3,7 @@ import { join, dirname } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { assert, expect, test } from 'vitest';
 import { create_builder } from './builder.js';
-import { posixify } from '../../utils/filesystem.js';
+import { posixify } from '../../utils/os.js';
 import { list_files } from '../utils.js';
 
 test('copy files', () => {

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

@@ -10,6 +10,7 @@ import { create_builder } from './builder.js';
  * @param {import('types').Logger} log
  * @param {import('types').RemoteChunk[]} remotes
  * @param {import('vite').ResolvedConfig} vite_config
+ * @param {string} out
  */
 export async function adapt(
 	config,
@@ -19,7 +20,8 @@ export async function adapt(
 	prerender_map,
 	log,
 	remotes,
-	vite_config
+	vite_config,
+	out
 ) {
 	// This is only called when adapter is truthy, so the cast is safe
 	const { name, adapt } = /** @type {import('@sveltejs/kit').Adapter} */ (config.kit.adapter);
@@ -35,7 +37,8 @@ export async function adapt(
 		prerender_map,
 		log,
 		remotes,
-		vite_config
+		vite_config,
+		out
 	});
 
 	await adapt(builder);

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

@@ -104,6 +104,7 @@ export function generate_manifest({
 			appDir: ${s(build_data.app_dir)},
 			appPath: ${s(build_data.app_path)},
 			assets: new Set(${s(assets)}),
+			base: ${s(build_data.base)},
 			mimeTypes: ${s(mime_types)},
 			_: {
 				client: ${uneval(build_data.client)},

packages/kit/src/core/postbuild/ambient.d.ts

@@ -0,0 +1,3 @@
+declare module '__SERVER__/index.js' {
+	export { Server } from '@sveltejs/kit';
+}