Do no fail if the source attribute is undefined in an unused named …

…export (#3211)

src/Module.ts

@@ -703,7 +703,7 @@ export default class Module {
 			const source = node.source.value;
 			this.sources.add(source);
 			this.exportAllSources.add(source);
-		} else if (node.source !== null) {
+		} else if (node.source instanceof Literal) {
 			// export { name } from './other'
 
 			const source = node.source.value;

test/function/samples/handle-missing-export-source/_config.js

@@ -0,0 +1,15 @@
+module.exports = {
+	description:
+		'does not fail if a pre-generated AST is omitting the source property of an unused named export (#3210)',
+	options: {
+		plugins: {
+			transform(code, id) {
+				if (id.endsWith('foo.js')) {
+					const ast = this.parse(code);
+					delete ast.body.find(node => node.type === 'ExportNamedDeclaration').source;
+					return { code, ast };
+				}
+			}
+		}
+	}
+};

test/function/samples/handle-missing-export-source/foo.js

@@ -0,0 +1 @@
+export const unused = 42;

test/function/samples/handle-missing-export-source/main.js

@@ -0,0 +1,3 @@
+import './foo.js';
+
+export const foo = 42;