fix bare imports in format: 'cjs' mode (sveltejs#4050)

Author: Conduitry

src/compiler/compile/create_module.ts

@@ -152,28 +152,34 @@ function cjs(
 
 	const internal_globals = get_internal_globals(globals, helpers);
 
-	const user_requires = imports.map(node => ({
-		type: 'VariableDeclaration',
-		kind: 'const',
-		declarations: [{
-			type: 'VariableDeclarator',
-			id: node.specifiers[0].type === 'ImportNamespaceSpecifier'
-				? { type: 'Identifier', name: node.specifiers[0].local.name }
-				: {
-					type: 'ObjectPattern',
-					properties: node.specifiers.map(s => ({
-						type: 'Property',
-						method: false,
-						shorthand: false,
-						computed: false,
-						key: s.type === 'ImportSpecifier' ? s.imported : { type: 'Identifier', name: 'default' },
-						value: s.local,
-						kind: 'init'
-					}))
-				},
-			init: x`require("${edit_source(node.source.value, sveltePath)}")`
-		}]
-	}));
+	const user_requires = imports.map(node => {
+		const init = x`require("${edit_source(node.source.value, sveltePath)}")`;
+		if (node.specifiers.length === 0) {
+			return b`${init};`;
+		}
+		return {
+			type: 'VariableDeclaration',
+			kind: 'const',
+			declarations: [{
+				type: 'VariableDeclarator',
+				id: node.specifiers[0].type === 'ImportNamespaceSpecifier'
+					? { type: 'Identifier', name: node.specifiers[0].local.name }
+					: {
+						type: 'ObjectPattern',
+						properties: node.specifiers.map(s => ({
+							type: 'Property',
+							method: false,
+							shorthand: false,
+							computed: false,
+							key: s.type === 'ImportSpecifier' ? s.imported : { type: 'Identifier', name: 'default' },
+							value: s.local,
+							kind: 'init'
+						}))
+					},
+				init
+			}]
+		};
+	});
 
 	const exports = module_exports.map(x => b`exports.${{ type: 'Identifier', name: x.as }} = ${{ type: 'Identifier', name: x.name }};`);