feat!: vite 6 support

packages/e2e-tests/kit-node/__tests__/kit.spec.ts

@@ -14,6 +14,7 @@ import {
 	readFileContent
 } from '~utils';
 
+import { version as viteVersion } from 'vite';
 import glob from 'tiny-glob';
 import path from 'node:path';
 import { describe, expect, it } from 'vitest';
@@ -347,11 +348,19 @@ describe('kit-node', () => {
 					['svelte', 'browser', 'module', 'jsnext:main', 'jsnext'],
 					`resolve.mainFields in ${filename}`
 				);
-				expectArrayEqual(
-					config.resolve.conditions,
-					['svelte'],
-					`resolve.conditions in ${filename}`
-				);
+				if (viteVersion.startsWith('6.')) {
+					expectArrayEqual(
+						config.resolve.conditions,
+						['browser', 'development|production', 'module', 'svelte'],
+						`resolve.conditions in ${filename}`
+					);
+				} else {
+					expectArrayEqual(
+						config.resolve.conditions,
+						['svelte'],
+						`resolve.conditions in ${filename}`
+					);
+				}
 			}
 		});
 	});

packages/e2e-tests/vite-ssr-esm/vite.config.js

@@ -14,6 +14,11 @@ export default defineConfig(({ command, mode }) => {
 				}
 			}
 		},
+		// TODO: investigate the condition issue. it's the same thing dominik and ben found.
+		// idk why it's only happening after https://github.com/vitejs/vite/pull/18395
+		ssr: {
+			noExternal: ['esm-env']
+		},
 		server: {
 			watch: {
 				// During tests we edit the files too fast and sometimes chokidar

packages/vite-plugin-svelte/src/index.js

@@ -18,6 +18,10 @@ import { saveSvelteMetadata } from './utils/optimizer.js';
 import { VitePluginSvelteCache } from './utils/vite-plugin-svelte-cache.js';
 import { loadRaw } from './utils/load-raw.js';
 import * as svelteCompiler from 'svelte/compiler';
+import {
+	VITE_CLIENT_RESOLVE_CONDITIONS,
+	VITE_SERVER_RESOLVE_CONDITIONS
+} from './utils/constants.js';
 
 /**
  * @param {Partial<import('./public.d.ts').Options>} [inlineOptions]
@@ -63,6 +67,18 @@ export function svelte(inlineOptions) {
 				log.debug('additional vite config', extraViteConfig, 'config');
 				return extraViteConfig;
 			},
+			// @ts-ignore Allow exist in vite 6
+			configEnvironment(name, config) {
+				config.resolve ??= {};
+				if (config.resolve.conditions == null) {
+					if (name === 'client') {
+						config.resolve.conditions = [...VITE_CLIENT_RESOLVE_CONDITIONS];
+					} else {
+						config.resolve.conditions = [...VITE_SERVER_RESOLVE_CONDITIONS];
+					}
+				}
+				config.resolve.conditions.push('svelte');
+			},
 
 			async configResolved(config) {
 				options = resolveOptions(options, config, cache);

packages/vite-plugin-svelte/src/utils/constants.js

@@ -2,6 +2,11 @@ import { createRequire } from 'node:module';
 
 export const VITE_RESOLVE_MAIN_FIELDS = ['browser', 'module', 'jsnext:main', 'jsnext'];
 
+// These two are required for Vite 6 only, as specifying conditions will remove the default ones,
+// like the `mainFields` option. Vite 6 is working on exposing these which we can use later.
+export const VITE_CLIENT_RESOLVE_CONDITIONS = ['module', 'browser', 'development|production'];
+export const VITE_SERVER_RESOLVE_CONDITIONS = ['module', 'node', 'development|production'];
+
 export const SVELTE_RESOLVE_MAIN_FIELDS = ['svelte'];
 
 export const SVELTE_IMPORTS = Object.entries(

packages/vite-plugin-svelte/src/utils/options.js

@@ -30,6 +30,7 @@ import {
 
 import { isCommonDepWithoutSvelteField } from './dependencies.js';
 import { VitePluginSvelteStats } from './vite-plugin-svelte-stats.js';
+import { isVite6 } from './vite-version.js';
 
 const allowedPluginOptions = new Set([
 	'include',
@@ -347,7 +348,9 @@ export async function buildExtraViteConfig(options, config) {
 	const extraViteConfig = {
 		resolve: {
 			dedupe: [...SVELTE_IMPORTS],
-			conditions: [...SVELTE_EXPORT_CONDITIONS]
+			// In Vite 6, we need to provide the default conditions too as it now replaces the default,
+			// instead of extending it. We set undefined here and extend it in the `configEnvironment` hook instead.
+			conditions: isVite6 ? undefined : [...SVELTE_EXPORT_CONDITIONS]
 		}
 		// this option is still awaiting a PR in vite to be supported
 		// see https://github.com/sveltejs/vite-plugin-svelte/issues/60

packages/vite-plugin-svelte/src/utils/vite-version.js

@@ -0,0 +1,6 @@
+import { version } from 'vite';
+
+/**
+ * @type {boolean}
+ */
+export const isVite6 = version.startsWith('6.');

packages/vite-plugin-svelte/types/index.d.ts.map

@@ -22,5 +22,5 @@
 		null,
 		null
 	],
-	"mappings": ";;;;aAIYA,OAAOA;;;;;;;;;;;;;kBAaFC,aAAaA;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;kBAgGbC,YAAYA;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;kBAkFZC,qBAAqBA;;;;;;;;;;;;;iBC1KtBC,MAAMA;iBCTNC,cAAcA;iBCgBRC,gBAAgBA"
+	"mappings": ";;;;aAIYA,OAAOA;;;;;;;;;;;;;kBAaFC,aAAaA;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;kBAgGbC,YAAYA;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;kBAkFZC,qBAAqBA;;;;;;;;;;;;;iBCtKtBC,MAAMA;iBCbNC,cAAcA;iBCgBRC,gBAAgBA"
 }