Fix crash when calling emitFile for chunks without a name

.changeset/eleven-planets-jam.md

@@ -0,0 +1,5 @@
+---
+'wmr': patch
+---
+
+Fix crash when calling `emitFile` for chunks without a name

packages/wmr/src/lib/rollup-plugin-container.js

@@ -124,15 +124,20 @@ export function createPluginContainer(plugins, opts = {}) {
 			return mod.info;
 		},
 		emitFile(assetOrFile) {
-			const { type, name, fileName } = assetOrFile;
-			const source = assetOrFile.type === 'asset' && assetOrFile.source;
+			const { type, fileName } = assetOrFile;
+			const name = type === 'chunk' ? assetOrFile.name || assetOrFile.id : assetOrFile.name;
+			const source = type === 'asset' && assetOrFile.source;
 			const id = String(++ids);
 			const filename = fileName || generateFilename({ type, name, source, fileName });
 			files.set(id, { id, name, filename });
-			if (source) {
-				if (type === 'chunk') {
+
+			if (type === 'chunk') {
+				if (source) {
 					throw Error(`emitFile({ type:"chunk" }) cannot include a source`);
 				}
+
+				// TODO: We probably need to process the chunk manually from here
+			} else if (source) {
 				if (opts.writeFile) opts.writeFile(filename, source);
 				else fs.writeFile(filename, source);
 			}

packages/wmr/test/fixtures/plugin-emit/public/index.html

@@ -0,0 +1,2 @@
+<h1>it doesn't work</h1>
+<script type="module" src="index.js"></script>

packages/wmr/test/fixtures/plugin-emit/public/index.js

@@ -0,0 +1 @@
+console.log('hey');

packages/wmr/test/fixtures/plugin-emit/public/worker.js

@@ -0,0 +1,3 @@
+addEventListener('message', () => {
+	postMessage('it works');
+});

packages/wmr/test/fixtures/plugin-emit/wmr.config.mjs

@@ -0,0 +1,25 @@
+export default function foo() {
+	return [
+		{
+			name: 'plugin-a',
+			async transform(code, id) {
+				if (!id.endsWith('index.js')) return;
+
+				const chunkRefId = this.emitFile({
+					id: 'public/worker.js',
+					type: 'chunk'
+				});
+
+				return {
+					code: `const url = new URL(import.meta.ROLLUP_FILE_URL_${chunkRefId}, import.meta.url);
+					const worker = new Worker(url, { type: "module" });
+					worker.addEventListener("message", e => {
+						document.querySelector("h1").textContent = e.data;
+					});
+					worker.postMessage("hello");`,
+					map: null
+				};
+			}
+		}
+	];
+}

packages/wmr/test/plugins/plugins.test.js

@@ -55,4 +55,14 @@ describe('config', () => {
 			await waitForMessage(instance.output, /oh no #3/);
 		});
 	});
+
+	it('should allow calls to emitFile without name', async () => {
+		await loadFixture('plugin-emit', env);
+		instance = await runWmrFast(env.tmp.path);
+		await getOutput(env, instance);
+		await withLog(instance.output, async () => {
+			await env.page.goto(await instance.address, { waitUntil: ['domcontentloaded', 'networkidle2'] });
+			expect(await env.page.content()).toMatch(/it works/);
+		});
+	});
 });