chore: read the Svelte config via @sveltejs/load-config

.changeset/package-load-config.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/package': patch
+---
+
+chore: read the Svelte config via `@sveltejs/load-config`

packages/package/package.json

@@ -20,6 +20,7 @@
 	"homepage": "https://svelte.dev",
 	"type": "module",
 	"dependencies": {
+		"@sveltejs/load-config": "^0.2.3",
 		"chokidar": "^5.0.0",
 		"semver": "^7.8.5",
 		"svelte2tsx": "~0.7.60"

packages/package/src/config.js

@@ -1,21 +1,18 @@
 import path from 'node:path';
 import process from 'node:process';
 import fs from 'node:fs';
-import { pathToFileURL } from 'node:url';
+import { loadConfig } from '@sveltejs/load-config';
 
 /**
- * Loads and validates the SvelteKit config
+ * Loads the Svelte config from `vite.config` or `svelte.config` in the current working directory
  * @returns {Promise<import('./types.js').Options['config']>}
  */
 export async function load_config() {
-	const { resolveConfig } = /** @type {typeof import('vite')} */ (
-		await import_peer('vite', process.cwd())
-	);
+	const result = await loadConfig(process.cwd(), { traverse: false });
 
-	const vite_config = await resolveConfig({}, 'build', 'production');
+	if (result && 'error' in result) throw result.error;
 
-	const plugin = vite_config.plugins.find((p) => p.name === 'vite-plugin-sveltekit-setup');
-	return plugin?.api.options ?? {};
+	return /** @type {import('./types.js').Options['config']} */ (result?.config ?? {});
 }
 
 /**
@@ -31,55 +28,3 @@ export function load_pkg_json(cwd = process.cwd()) {
 
 	return JSON.parse(fs.readFileSync(pkg_json_file, 'utf-8'));
 }
-
-/**
- * Resolve a dependency relative to the current working directory,
- * rather than relative to this package (but falls back to trying that, if necessary)
- * @param {string} dependency
- * @param {string} root
- */
-async function import_peer(dependency, root) {
-	try {
-		return await import(/* @vite-ignore */ pathToFileURL(resolve_peer(dependency, root)).href);
-	} catch {
-		// eslint-disable-next-line kit-node-custom/require-path-to-file-url -- bare package specifier, not a path
-		return await import(/* @vite-ignore */ dependency);
-	}
-}
-
-/**
- * Resolves a peer dependency relative to the current working directory. Duplicated with `packages/adapter-auto`
- * @param {string} dependency
- * @param {string} root
- */
-function resolve_peer(dependency, root) {
-	let [name, ...parts] = dependency.split('/');
-	if (name[0] === '@') name += `/${parts.shift()}`;
-
-	let dir = root;
-
-	while (!fs.existsSync(`${dir}/node_modules/${name}/package.json`)) {
-		if (dir === (dir = path.dirname(dir))) {
-			throw new Error(
-				`Could not resolve peer dependency "${name}" relative to your project — please install it and try again.`
-			);
-		}
-	}
-
-	const pkg_dir = `${dir}/node_modules/${name}`;
-	const pkg = JSON.parse(fs.readFileSync(`${pkg_dir}/package.json`, 'utf-8'));
-
-	const subpackage = ['.', ...parts].join('/');
-
-	let exported = pkg.exports[subpackage];
-
-	while (typeof exported !== 'string') {
-		if (!exported) {
-			throw new Error(`Could not find valid "${subpackage}" export in ${name}/package.json`);
-		}
-
-		exported = exported['import'] ?? exported['default'];
-	}
-
-	return path.resolve(pkg_dir, exported);
-}