support custom Vite config locations

.changeset/ninety-glasses-exercise.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Support custom Vite config locations

packages/kit/src/vite/build/build_server.js

@@ -112,6 +112,7 @@ export class Server {
  * @param {{
  *   cwd: string;
  *   config: import('types').ValidatedConfig;
+ *   vite_config: import('vite').ResolvedConfig;
  *   vite_config_env: import('vite').ConfigEnv;
  *   manifest_data: import('types').ManifestData;
  *   build_dir: string;
@@ -124,6 +125,7 @@ export async function build_server(options, client) {
 	const {
 		cwd,
 		config,
+		vite_config,
 		vite_config_env,
 		manifest_data,
 		build_dir,
@@ -188,11 +190,9 @@ export async function build_server(options, client) {
 		})
 	);
 
-	const vite_config = await get_vite_config(vite_config_env);
-
 	const merged_config = merge_vite_configs(
 		get_default_config({ config, input, ssr: true, outDir: `${output_dir}/server` }),
-		vite_config
+		await get_vite_config(vite_config, vite_config_env)
 	);
 
 	remove_svelte_kit(merged_config);

packages/kit/src/vite/build/build_service_worker.js

@@ -7,6 +7,7 @@ import { assets_base, remove_svelte_kit } from './utils.js';
 /**
  * @param {{
  *   config: import('types').ValidatedConfig;
+ *   vite_config: import('vite').ResolvedConfig;
  *   vite_config_env: import('vite').ConfigEnv;
  *   manifest_data: import('types').ManifestData;
  *   output_dir: string;
@@ -16,7 +17,7 @@ import { assets_base, remove_svelte_kit } from './utils.js';
  * @param {import('vite').Manifest} client_manifest
  */
 export async function build_service_worker(
-	{ config, vite_config_env, manifest_data, output_dir, service_worker_entry_file },
+	{ config, vite_config, vite_config_env, manifest_data, output_dir, service_worker_entry_file },
 	prerendered,
 	client_manifest
 ) {
@@ -63,8 +64,7 @@ export async function build_service_worker(
 			.trim()
 	);
 
-	const vite_config = await get_vite_config(vite_config_env);
-	const merged_config = merge_vite_configs(vite_config, {
+	const merged_config = merge_vite_configs(await get_vite_config(vite_config, vite_config_env), {
 		base: assets_base(config.kit),
 		build: {
 			lib: {

packages/kit/src/vite/index.js

@@ -288,6 +288,7 @@ function kit() {
 			const options = {
 				cwd,
 				config: svelte_config,
+				vite_config,
 				vite_config_env,
 				build_dir: paths.build_dir, // TODO just pass `paths`
 				manifest_data,

packages/kit/src/vite/utils.js

@@ -4,15 +4,22 @@ import { loadConfigFromFile } from 'vite';
 import { get_runtime_directory } from '../core/utils.js';
 
 /**
+ * @param {import('vite').ResolvedConfig} config
  * @param {import('vite').ConfigEnv} config_env
  * @return {Promise<import('vite').UserConfig>}
  */
-export async function get_vite_config(config_env) {
-	const config = (await loadConfigFromFile(config_env))?.config;
-	if (!config) {
+export async function get_vite_config(config, config_env) {
+	const loaded = await loadConfigFromFile(
+		config_env,
+		config.configFile,
+		undefined,
+		config.logLevel
+	);
+
+	if (!loaded) {
 		throw new Error('Could not load Vite config');
 	}
-	return { ...config, mode: config_env.mode };
+	return { ...loaded.config, mode: config_env.mode };
 }
 
 /**

packages/kit/test/apps/options/package.json

@@ -3,9 +3,9 @@
 	"private": true,
 	"version": "0.0.1",
 	"scripts": {
-		"dev": "vite dev",
-		"build": "vite build --mode custom",
-		"preview": "vite preview",
+		"dev": "vite dev -c vite.custom.config.js",
+		"build": "vite build -c vite.custom.config.js --mode custom",
+		"preview": "vite preview -c vite.custom.config.js",
 		"prepare": "node ../../cli.js sync",
 		"check": "tsc && svelte-check",
 		"test": "npm run test:dev && npm run test:build",