Handle shimming missing exports when preserving modules (#4971)

src/Module.ts

@@ -747,7 +747,11 @@ export default class Module {
 		// Modules where this.ast is missing have been loaded via this.load and are
 		// not yet fully processed, hence they cannot be included.
 		return (
-			this.ast && (this.ast.included || this.namespace.included || this.importedFromNotTreeshaken)
+			this.ast &&
+			(this.ast.included ||
+				this.namespace.included ||
+				this.importedFromNotTreeshaken ||
+				this.exportShimVariable.included)
 		);
 	}
 

test/function/samples/missing-export-preserve-modules/_config.js

@@ -0,0 +1,19 @@
+const path = require('node:path');
+
+module.exports = defineTest({
+	description: 'supports shimming missing exports when preserving modules',
+	options: {
+		shimMissingExports: true,
+		output: {
+			preserveModules: true
+		}
+	},
+	warnings: [
+		{
+			binding: 'bar',
+			code: 'SHIMMED_EXPORT',
+			exporter: path.join(__dirname, 'foo.js'),
+			message: 'Missing export "bar" has been shimmed in module "foo.js".'
+		}
+	]
+});

test/function/samples/missing-export-preserve-modules/foo.js

@@ -0,0 +1 @@
+export const foo = 'foo';

test/function/samples/missing-export-preserve-modules/main.js

@@ -0,0 +1,2 @@
+import { bar } from './foo';
+assert.strictEqual(bar, undefined);