[fix] copy essentials files from root on packaging

.changeset/lazy-mice-smile.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+copy essential root files on `svelte-kit package`

documentation/docs/12-packaging.md

@@ -12,7 +12,7 @@ Running `svelte-kit package` will take the contents of `src/lib` and generate a
 
 - All the files in `src/lib`, unless you [configure](#configuration-package) custom `include`/`exclude` options. Svelte components will be preprocessed, TypeScript files will be transpiled to JavaScript.
 - Type definitions (`d.ts` files) which are generated for Svelte, JavaScript and TypeScript files. You need to install `typescript >= 4.0.0` and `svelte2tsx >= 0.4.1` for this. Type definitions are placed next to their implementation, hand-written `d.ts` files are copied over as is.
-- A `package.json` that copies the `name`, `version`, `description`, `keywords`, `homepage`, `bugs`, `license`, `author`, `contributors`, `funding`, `repository`, `dependencies`, `private` and `publishConfig` fields from the root of the project, and adds a `"type": "module"` and an `"exports"` field
+- A `package.json` that copies the `name`, `version`, `description`, `keywords`, `homepage`, `bugs`, `license`, `author`, `contributors`, `funding`, `repository`, `dependencies`, `private`, `files` and `publishConfig` fields from the root of the project, and adds a `"type": "module"` and an `"exports"` field
 
 The `"exports"` field contains the package's entry points. By default, all files in `src/lib` will be treated as an entry point unless they start with (or live in a directory that starts with) an underscore, but you can [configure](#configuration-package) this behaviour. If you have a `src/lib/index.js` or `src/lib/index.svelte` file, it will be treated as the package root.
 

packages/kit/src/core/make_package/essential_files.js

@@ -0,0 +1 @@
+export default ['README', 'LICENSE', 'CHANGELOG', '.gitignore', '.npmignore'];

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

@@ -4,6 +4,7 @@ import { createRequire } from 'module';
 import * as path from 'path';
 import { preprocess } from 'svelte/compiler';
 import { mkdirp, rimraf } from '../filesystem/index.js';
+import essential_files from './essential_files.js';
 
 /**
  * @param {import('types/config').ValidatedConfig} config
@@ -39,6 +40,7 @@ export async function make_package(config, cwd = process.cwd()) {
 		repository: pkg.repository,
 		dependencies: pkg.dependencies,
 		private: pkg.private,
+		files: pkg.files,
 		publishConfig: pkg.publishConfig,
 		type: 'module',
 		/** @type {Record<string, string>} */
@@ -106,11 +108,17 @@ export async function make_package(config, cwd = process.cwd()) {
 		JSON.stringify(package_pkg, null, '  ')
 	);
 
-	const project_readme = path.join(cwd, 'README.md');
-	const package_readme = path.join(cwd, config.kit.package.dir, 'README.md');
+	const whitelist = fs.readdirSync(cwd).filter((file) => {
+		const lowercased = file.toLowerCase();
+		return essential_files.some((name) => lowercased.startsWith(name.toLowerCase()));
+	});
+	for (const pathname of whitelist) {
+		const full_path = path.join(cwd, pathname);
+		if (fs.lstatSync(full_path).isDirectory()) continue; // just to be sure
 
-	if (fs.existsSync(project_readme) && !fs.existsSync(package_readme)) {
-		fs.copyFileSync(project_readme, package_readme);
+		const package_path = path.join(cwd, config.kit.package.dir, pathname);
+		if (fs.existsSync(package_path)) continue;
+		fs.copyFileSync(full_path, package_path);
 	}
 }