[feat] Ignore adapter build files

.changeset/big-countries-pump.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Add public API to let adapters update .gitignore and files alike

documentation/docs/10-adapters.md

@@ -31,6 +31,15 @@ export default {
 };
 ```
 
+Some adapters may modify your project's `.gitignore`, `.prettierignore` and `.eslintignore` to include their build output. In case you don't want those patterns included you can comment them out: 
+
+```diff
+.svelte-kit
+.env
+
+- build
++ # build
+```
 A variety of official adapters exist for serverless platforms...
 
 - [`adapter-cloudflare-workers`](https://github.com/sveltejs/kit/tree/master/packages/adapter-cloudflare-workers) — for [Cloudflare Workers](https://developers.cloudflare.com/workers/)

documentation/docs/80-adapter-api.md

@@ -26,6 +26,7 @@ The types for `Adapter` and its parameters are available in [types/config.d.ts](
 Within the `adapt` method, there are a number of things that an adapter should do:
 
 - Clear out the build directory
+- Call `utils.update_ignores` to ignore build output in existing `.gitignore`, `.eslintignore` and `.prettierignore` files at the location of `svelte.config.js`
 - Output code that:
   - Calls `init`
   - Converts from the patform's request to a [SvelteKit request](#hooks-handle), calls `render`, and converts from a [SvelteKit response](#hooks-handle) to the platform's

packages/adapter-cloudflare-workers/index.js

@@ -16,6 +16,8 @@ export default function () {
 
 			const files = fileURLToPath(new URL('./files', import.meta.url));
 
+			utils.update_ignores({ patterns: [bucket, entrypoint] });
+
 			utils.rimraf(bucket);
 			utils.rimraf(entrypoint);
 

packages/adapter-netlify/index.js

@@ -17,6 +17,8 @@ export default function () {
 
 			const files = fileURLToPath(new URL('./files', import.meta.url));
 
+			utils.update_ignores({ patterns: [publish, functions] });
+
 			utils.log.minor('Generating serverless function...');
 			utils.copy(join(files, 'entry.js'), '.svelte-kit/netlify/entry.js');
 

packages/adapter-node/index.js

@@ -36,6 +36,7 @@ export default function ({
 		name: '@sveltejs/adapter-node',
 
 		async adapt({ utils, config }) {
+			utils.update_ignores({ patterns: [out] });
 			utils.log.minor('Copying assets');
 			const static_directory = join(out, 'assets');
 			utils.copy_client_files(static_directory);

packages/adapter-static/index.js

@@ -11,6 +11,7 @@ export default function ({ pages = 'build', assets = pages, fallback } = {}) {
 		name: '@sveltejs/adapter-static',
 
 		async adapt({ utils }) {
+			utils.update_ignores({ patterns: [pages, assets] });
 			utils.copy_static_files(assets);
 			utils.copy_client_files(assets);
 

packages/adapter-vercel/index.js

@@ -10,6 +10,8 @@ export default function () {
 
 		async adapt({ utils }) {
 			const dir = '.vercel_build_output';
+
+			utils.update_ignores({ patterns: [dir] });
 			utils.rimraf(dir);
 
 			const files = fileURLToPath(new URL('./files', import.meta.url));

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

@@ -1,6 +1,7 @@
 import { SVELTE_KIT } from '../constants.js';
 import { copy, rimraf, mkdirp } from '../filesystem/index.js';
 import { prerender } from './prerender.js';
+import fs from 'fs';
 
 /**
  *
@@ -47,6 +48,25 @@ export function get_utils({ cwd, config, build_data, log }) {
 					log
 				});
 			}
+		},
+
+		/** @param {{patterns: string[], log?: boolean}} options */
+		update_ignores({ patterns, log = true }) {
+			const target = '.gitignore';
+			if (!fs.existsSync(target)) return;
+
+			const file = fs.readFileSync(target, { encoding: 'utf-8' });
+			const eol = file.includes('\r\n') ? '\r\n' : '\n';
+			const lines = file.split(eol);
+			const new_lines = new Set(patterns);
+			// remove repeated lines
+			for (const line of lines) {
+				// this will prevent commented ignores to be reinserted
+				new_lines.delete(line.replace(/#\s*/, ''));
+			}
+			if (new_lines.size === 0) return;
+			fs.writeFileSync(target, [...lines, ...new_lines].join(eol));
+			if (log) this.log.success(`Updated ${target}`);
 		}
 	};
 }

packages/kit/types/config.d.ts

@@ -9,6 +9,7 @@ export type AdapterUtils = {
 	copy_server_files: (dest: string) => void;
 	copy_static_files: (dest: string) => void;
 	copy: (from: string, to: string, filter?: (basename: string) => boolean) => void;
+	update_ignores: ({ patterns, log }: { patterns: string[]; log?: boolean }) => void;
 	prerender: ({
 		all,
 		dest,