test unknown format, and improve error message

src/generators/shared/utils/wrapModule.ts

@@ -1,4 +1,5 @@
 import deindent from '../../../utils/deindent';
+import list from '../../../utils/list';
 import { CompileOptions, ModuleFormat, Node } from '../../../interfaces';
 
 interface Dependency {
@@ -65,7 +66,7 @@ export default function wrapModule(
 	if (format === 'umd') return umd(code, name, options, banner, dependencies);
 	if (format === 'eval') return expr(code, name, options, banner, dependencies);
 
-	throw new Error(`Not implemented: ${format}`);
+	throw new Error(`options.format is invalid (must be ${list(Object.keys(wrappers))})`);
 }
 
 function es(

src/validate/html/validateEventHandler.ts

@@ -1,5 +1,5 @@
 import flattenReference from '../../utils/flattenReference';
-import list from '../utils/list';
+import list from '../../utils/list';
 import { Validator } from '../index';
 import validCalleeObjects from '../../utils/validCalleeObjects';
 import { Node } from '../../interfaces';

src/validate/html/validateWindow.ts

@@ -1,6 +1,6 @@
 import flattenReference from '../../utils/flattenReference';
 import fuzzymatch from '../utils/fuzzymatch';
-import list from '../utils/list';
+import list from '../../utils/list';
 import validateEventHandler from './validateEventHandler';
 import { Validator } from '../index';
 import { Node } from '../../interfaces';

test/formats/index.js

@@ -218,4 +218,14 @@ describe("formats", () => {
 			return testEval(code, "Foo", { answer: 42 }, `<div>42</div>`);
 		});
 	});
+
+	describe('unknown format', () => {
+		it('throws an error', () => {
+			assert.throws(() => {
+				svelte.compile('', {
+					format: 'nope'
+				});
+			}, /options.format is invalid \(must be es, amd, cjs, iife, umd or eval\)/);
+		});
+	});
 });