fix: add svelte lib without components to noExternal

.changeset/modern-horses-reply.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/vite-plugin-svelte': patch
+---
+
+Svelte libraries without any Svelte components are also added to ssr.noExternal

packages/e2e-tests/_test_dependencies/esm-only/package.json

@@ -6,7 +6,7 @@
   "module": "index.js",
   "files": [
     "package.json",
-    "index.cjs"
+    "index.js"
   ],
   "exports":{
     ".": {

packages/e2e-tests/_test_dependencies/svelte-api-only/index.js

@@ -0,0 +1,5 @@
+import { setContext } from 'svelte';
+
+export function setSomeContext() {
+	setContext('svelte-api-only', true);
+}

packages/e2e-tests/_test_dependencies/svelte-api-only/package.json

@@ -0,0 +1,18 @@
+{
+  "version": "1.0.0",
+  "private": true,
+  "name": "e2e-test-dep-svelte-api-only",
+  "main": "index.js",
+  "module": "index.js",
+  "files": [
+    "package.json",
+    "index.js"
+  ],
+  "exports":{
+    ".": {
+      "import": "./index.js"
+    },
+    "./package.json": "./package.json"
+  },
+  "type": "module"
+}

packages/e2e-tests/kit-node/package.json

@@ -10,6 +10,7 @@
   "devDependencies": {
     "@sveltejs/adapter-node": "^1.0.0-next.46",
     "@sveltejs/kit": "^1.0.0-next.165",
+    "e2e-test-dep-svelte-api-only": "workspace:*",
     "svelte": "^3.42.4"
   },
   "type": "module",

packages/e2e-tests/kit-node/src/routes/index.svelte

@@ -22,13 +22,15 @@
 	import Counter from '$lib/Counter.svelte';
 	// eslint-disable-next-line node/no-missing-import
 	import Child from '$lib/Child.svelte';
+	import { setSomeContext } from 'e2e-test-dep-svelte-api-only';
 	export let load_status = 'NOT_LOADED';
 	let mount_status = 'BEFORE_MOUNT';
 	onMount(async () => {
 		const isSSR = (await import('../client-only-module.js')).default;
 		console.log(`onMount dynamic imported isSSR: ${isSSR}`);
 		mount_status = 'AFTER_MOUNT';
 	});
+	setSomeContext();
 </script>
 
 <main>

packages/vite-plugin-svelte/src/utils/dependencies.ts

@@ -40,11 +40,13 @@ function getSvelteDependencies(
 	const localRequire = createRequire(`${pkgDir}/package.json`);
 	const resolvedDeps = deps
 		.map((dep) => resolveDependencyData(dep, localRequire))
-		.filter((depData) => !!depData && isSvelte(depData.pkg)) as DependencyData[];
-	// @ts-ignore
+		.filter(Boolean) as DependencyData[];
 	for (const { pkg, dir } of resolvedDeps) {
-		result.push({ name: pkg.name, pkg, dir, path });
-		if (pkg.dependencies) {
+		const type = getSvelteDependencyType(pkg);
+		if (!type) continue;
+		result.push({ name: pkg.name, type, pkg, dir, path });
+		// continue crawling for component libraries so we can optimize them, js libraries are fine
+		if (type === 'component-library' && pkg.dependencies) {
 			let dependencyNames = Object.keys(pkg.dependencies);
 			const circular = dependencyNames.filter((name) => path.includes(name));
 			if (circular.length > 0) {
@@ -102,10 +104,24 @@ function parsePkg(dir: string, silent = false): Pkg | void {
 	}
 }
 
-function isSvelte(pkg: Pkg) {
+function getSvelteDependencyType(pkg: Pkg): SvelteDependencyType | undefined {
+	if (isSvelteComponentLib(pkg)) {
+		return 'component-library';
+	} else if (isSvelteLib(pkg)) {
+		return 'js-library';
+	} else {
+		return undefined;
+	}
+}
+
+function isSvelteComponentLib(pkg: Pkg) {
 	return !!pkg.svelte;
 }
 
+function isSvelteLib(pkg: Pkg) {
+	return !!pkg.dependencies?.svelte || !!pkg.peerDependencies?.svelte;
+}
+
 const COMMON_DEPENDENCIES_WITHOUT_SVELTE_FIELD = [
 	'@lukeed/uuid',
 	'@sveltejs/vite-plugin-svelte',
@@ -178,16 +194,22 @@ interface DependencyData {
 
 export interface SvelteDependency {
 	name: string;
+	type: SvelteDependencyType;
 	dir: string;
 	pkg: Pkg;
 	path: string[];
 }
 
+// component-library => exports svelte components
+// js-library        => only uses svelte api, no components
+export type SvelteDependencyType = 'component-library' | 'js-library';
+
 export interface Pkg {
 	name: string;
 	svelte?: string;
 	dependencies?: DependencyList;
 	devDependencies?: DependencyList;
+	peerDependencies?: DependencyList;
 	[key: string]: any;
 }
 

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

@@ -199,7 +199,7 @@ export function buildExtraViteConfig(
 
 	if (configEnv.command === 'serve') {
 		extraViteConfig.optimizeDeps = buildOptimizeDepsForSvelte(
-			svelteDeps,
+			svelteDeps.filter((dep) => dep.type === 'component-library'),
 			options,
 			config.optimizeDeps
 		);