feat(adapter-node): precompress (gzip & brotli) assets

sirv supports using precompressed assets but they are not generated during the build. This PR precompresses html, js, json, css, svg, and xml assets using gzip and brotli during the adapt phase which allows sirv to use these.

.changeset/clever-eagles-live.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-node': patch
+---
+
+precompress assets and prerendered pages (html,js,json,css,svg,xml)

packages/adapter-node/README.md

@@ -15,6 +15,7 @@ export default {
 		adapter: adapter({
 			// default options are shown
 			out: 'build'
+			precompress: false,
 		})
 	}
 };
@@ -26,6 +27,10 @@ export default {
 
 The directory to build the server to. It defaults to `build` — i.e. `node build` would start the server locally after it has been created.
 
+### precompress
+
+Enables precompressing using gzip and brotli for assets and prerendered pages. It defaults to `false`.
+
 ## Environment variables
 
 By default, the server will accept connections on `0.0.0.0` using port 3000. These can be customised with the `PORT` and `HOST` environment variables:

packages/adapter-node/index.d.ts

@@ -1,3 +1,6 @@
-declare function plugin(options?: { out?: string }): import('@sveltejs/kit').Adapter;
+declare function plugin(options?: {
+	out?: string;
+	precompress?: boolean;
+}): import('@sveltejs/kit').Adapter;
 
 export = plugin;

packages/adapter-node/index.js

@@ -1,14 +1,21 @@
-import { readFileSync } from 'fs';
+import { readFileSync, statSync, createReadStream, createWriteStream } from 'fs';
 import { join } from 'path';
 import { fileURLToPath } from 'url';
+import { pipeline } from 'stream';
+import { promisify } from 'util';
+import zlib from 'zlib';
 import esbuild from 'esbuild';
+import glob from 'tiny-glob';
+
+const pipe = promisify(pipeline);
 
 /**
  * @param {{
  *   out?: string;
+ *   precompress?: boolean
  * }} options
  */
-export default function ({ out = 'build' } = {}) {
+export default function ({ out = 'build', precompress } = {}) {
 	/** @type {import('@sveltejs/kit').Adapter} */
 	const adapter = {
 		name: '@sveltejs/adapter-node',
@@ -19,6 +26,11 @@ export default function ({ out = 'build' } = {}) {
 			utils.copy_client_files(static_directory);
 			utils.copy_static_files(static_directory);
 
+			if (precompress) {
+				utils.log.minor('Compressing assets');
+				await compress(static_directory);
+			}
+
 			utils.log.minor('Building server');
 			const files = fileURLToPath(new URL('./files', import.meta.url));
 			utils.copy(files, '.svelte-kit/node');
@@ -36,8 +48,52 @@ export default function ({ out = 'build' } = {}) {
 			await utils.prerender({
 				dest: `${out}/prerendered`
 			});
+			if (precompress) {
+				utils.log.minor('Compressing prerendered pages');
+				await compress(`${out}/prerendered`);
+			}
 		}
 	};
 
 	return adapter;
 }
+
+/**
+ * @param {string} directory
+ */
+async function compress(directory) {
+	const files = await glob('**/*.{html,js,json,css,svg,xml}', {
+		cwd: directory,
+		dot: true,
+		absolute: true,
+		filesOnly: true
+	});
+
+	await Promise.all(
+		files.map((file) => Promise.all([compress_file(file, 'gz'), compress_file(file, 'br')]))
+	);
+}
+
+/**
+ * @param {string} file
+ * @param {'gz' | 'br'} format
+ */
+async function compress_file(file, format = 'gz') {
+	const compress =
+		format == 'br'
+			? zlib.createBrotliCompress({
+					params: {
+						[zlib.constants.BROTLI_PARAM_MODE]: zlib.constants.BROTLI_MODE_TEXT,
+						[zlib.constants.BROTLI_PARAM_QUALITY]: zlib.constants.BROTLI_MAX_QUALITY,
+						[zlib.constants.BROTLI_PARAM_SIZE_HINT]: statSync(file).size
+					}
+			  })
+			: zlib.createGzip({
+					level: zlib.constants.Z_BEST_COMPRESSION
+			  });
+
+	const source = createReadStream(file);
+	const destination = createWriteStream(`${file}.${format}`);
+
+	await pipe(source, compress, destination);
+}

packages/adapter-node/package.json

@@ -21,7 +21,8 @@
 		"prepublishOnly": "npm run build"
 	},
 	"dependencies": {
-		"esbuild": "^0.12.5"
+		"esbuild": "^0.12.5",
+		"tiny-glob": "^0.2.9"
 	},
 	"devDependencies": {
 		"@rollup/plugin-json": "^4.1.0",

packages/adapter-node/src/server.js

@@ -17,14 +17,13 @@ const paths = {
 };
 
 export function createServer({ render }) {
-	const mutable = (dir) =>
-		sirv(dir, {
-			etag: true,
-			maxAge: 0
-		});
-
 	const prerendered_handler = fs.existsSync(paths.prerendered)
-		? mutable(paths.prerendered)
+		? sirv(paths.assets, {
+				etag: true,
+				maxAge: 0,
+				gzip: true,
+				brotli: true
+		  })
 		: noop_handler;
 
 	const assets_handler = fs.existsSync(paths.assets)