chore(cli): add integ test for asset bundling in a stage (#21294)

We recently had an issue where a PR broke asset bundling for stacks that
were created under a stage. This PR adds an integration test that
deploys a Stack under a Stage that contains lambda function with an asset.


----

### All Submissions:

* [ ] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md)

### Adding new Unconventional Dependencies:

* [ ] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/main/INTEGRATION_TESTS.md)?
	* [ ] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: corymhall

packages/aws-cdk/test/integ/cli/app/app.js

@@ -308,6 +308,19 @@ class ConditionalResourceStack extends cdk.Stack {
   }
 }
 
+class BundlingStage extends cdk.Stage {
+  constructor(parent, id, props) {
+    super(parent, id, props);
+    const stack = new cdk.Stack(this, 'BundlingStack');
+
+    new lambda.Function(stack, 'Handler', {
+      code: lambda.Code.fromAsset(path.join(__dirname, 'lambda')),
+      handler: 'index.handler',
+      runtime: lambda.Runtime.NODEJS_16_X,
+    });
+  }
+}
+
 class SomeStage extends cdk.Stage {
   constructor(parent, id, props) {
     super(parent, id, props);
@@ -392,6 +405,8 @@ switch (stackSet) {
     new BuiltinLambdaStack(app, `${stackPrefix}-builtin-lambda-function`);
 
     new ImportableStack(app, `${stackPrefix}-importable-stack`);
+
+    new BundlingStage(app, `${stackPrefix}-bundling-stage`);
     break;
 
   case 'stage-using-context':

packages/aws-cdk/test/integ/cli/cli.integtest.ts

@@ -61,6 +61,13 @@ integTest('Construct with builtin Lambda function', withDefaultFixture(async (fi
   await fixture.cdkDestroy('builtin-lambda-function');
 }));
 
+// this is to ensure that asset bundling for apps under a stage does not break
+integTest('Stage with bundled Lambda function', withDefaultFixture(async (fixture) => {
+  await fixture.cdkDeploy('bundling-stage/BundlingStack');
+  fixture.log('Setup complete!');
+  await fixture.cdkDestroy('bundling-stage/BundlingStack');
+}));
+
 integTest('Two ways of showing the version', withDefaultFixture(async (fixture) => {
   const version1 = await fixture.cdk(['version'], { verbose: false });
   const version2 = await fixture.cdk(['--version'], { verbose: false });