fix: overwrite nodenext option when transpiling

.changeset/wild-rats-sell.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/package': patch
+---
+
+fix: overwrite nodenext option when transpiling

packages/kit/package.json

@@ -34,7 +34,7 @@
 		"dts-buddy": "^0.2.4",
 		"rollup": "^3.29.4",
 		"svelte": "^4.2.2",
-		"svelte-preprocess": "^5.0.4",
+		"svelte-preprocess": "^5.1.1",
 		"typescript": "^4.9.4",
 		"vite": "^4.4.9",
 		"vitest": "^0.34.5"

packages/package/package.json

@@ -21,7 +21,7 @@
 		"@types/node": "^16.18.6",
 		"@types/semver": "^7.5.0",
 		"svelte": "^4.2.2",
-		"svelte-preprocess": "^5.0.4",
+		"svelte-preprocess": "^5.1.1",
 		"typescript": "^4.9.4",
 		"uvu": "^0.5.6"
 	},

packages/package/src/typescript.js

@@ -67,8 +67,15 @@ export async function emit_dts(input, output, cwd, alias, files) {
  */
 export async function transpile_ts(filename, source) {
 	const ts = await try_load_ts();
+	const options = load_tsconfig(filename, ts);
+	// transpileModule treats NodeNext as CommonJS because it doesn't read the package.json. Therefore we need to override it.
+	// Also see https://github.com/microsoft/TypeScript/issues/53022 (the filename workaround doesn't work).
 	return ts.transpileModule(source, {
-		compilerOptions: load_tsconfig(filename, ts),
+		compilerOptions: {
+			...options,
+			module: ts.ModuleKind.ESNext,
+			moduleResolution: ts.ModuleResolutionKind.NodeJs // switch this to bundler in the next major, although it probably doesn't make a difference
+		},
 		fileName: filename
 	}).outputText;
 }

packages/package/test/fixtures/typescript-nodenext/expected/Test.svelte

@@ -0,0 +1,8 @@
+<script>
+import { createEventDispatcher } from 'svelte';
+export const astring = 'potato';
+const dispatch = createEventDispatcher();
+dispatch('event', true);
+</script>
+
+<slot {astring} />

packages/package/test/fixtures/typescript-nodenext/expected/Test.svelte.d.ts

@@ -0,0 +1,23 @@
+import { SvelteComponent } from 'svelte';
+declare const __propDef: {
+	props: {
+		astring?: string;
+	};
+	events: {
+		event: CustomEvent<boolean>;
+	} & {
+		[evt: string]: CustomEvent<any>;
+	};
+	slots: {
+		default: {
+			astring: string;
+		};
+	};
+};
+export type TestProps = typeof __propDef.props;
+export type TestEvents = typeof __propDef.events;
+export type TestSlots = typeof __propDef.slots;
+export default class Test extends SvelteComponent<TestProps, TestEvents, TestSlots> {
+	get astring(): string;
+}
+export {};

packages/package/test/fixtures/typescript-nodenext/expected/index.d.ts

@@ -0,0 +1 @@
+export { default as Test } from './Test.svelte';

packages/package/test/fixtures/typescript-nodenext/expected/index.js

@@ -0,0 +1 @@
+export { default as Test } from './Test.svelte';

packages/package/test/fixtures/typescript-nodenext/package.json

@@ -0,0 +1,16 @@
+{
+	"name": "typescript-nodenext",
+	"private": true,
+	"version": "1.0.0",
+	"description": "typescript package using nodenext",
+	"type": "module",
+	"peerDependencies": {
+		"svelte": "^4.0.0"
+	},
+	"exports": {
+		".": {
+			"types": "./dist/index.d.ts",
+			"svelte": "./dist/index.js"
+		}
+	}
+}

packages/package/test/fixtures/typescript-nodenext/src/lib/Test.svelte

@@ -0,0 +1,9 @@
+<script lang="ts">
+	import { createEventDispatcher } from 'svelte';
+	export const astring: string = 'potato';
+
+	const dispatch = createEventDispatcher<{ event: boolean }>();
+	dispatch('event', true);
+</script>
+
+<slot {astring} />

packages/package/test/fixtures/typescript-nodenext/src/lib/index.ts

@@ -0,0 +1 @@
+export { default as Test } from './Test.svelte';

packages/package/test/fixtures/typescript-nodenext/svelte.config.js

@@ -0,0 +1,5 @@
+import preprocess from 'svelte-preprocess';
+
+export default {
+	preprocess: preprocess({})
+};

packages/package/test/fixtures/typescript-nodenext/tsconfig.json

@@ -0,0 +1,7 @@
+{
+	"compilerOptions": {
+		"target": "ESNext",
+		"module": "NodeNext",
+		"moduleResolution": "NodeNext"
+	}
+}

packages/package/test/index.js

@@ -127,6 +127,10 @@ test('create standard package with typescript', async () => {
 	await test_make_package('typescript');
 });
 
+test('create standard package with typescript using nodenext', async () => {
+	await test_make_package('typescript-nodenext');
+});
+
 test('create package and assets are not tampered', async () => {
 	await test_make_package('assets');
 });