fix(cli): --hotswap does not handle CfnOutput change correctly (#…

…21461)

closes #19998

Although there are other types of diffs (other than `outputs`) that are currently ignored by hotswap, I leave them as-is since no one is complaining about the behavior and it may break someone's hotswap experience.

https://github.com/aws/aws-cdk/blob/3853728c699bd9c47b60fcc24ac6a8b7d65306fe/packages/%40aws-cdk/cloudformation-diff/lib/diff/types.ts#L10-L21

----

### All Submissions:

* [X] 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*

packages/aws-cdk/lib/api/hotswap-deployments.ts

@@ -68,6 +68,11 @@ async function findAllHotswappableChanges(
   sdk: ISDK,
   nestedStackNames: { [nestedStackName: string]: NestedStackNames },
 ): Promise<HotswapOperation[] | undefined> {
+  // Skip hotswap if there is any change on stack outputs
+  if (stackChanges.outputs.differenceCount > 0) {
+    return undefined;
+  }
+
   const resourceDifferences = getStackResourceDifferences(stackChanges);
 
   let foundNonHotswappableChange = false;

packages/aws-cdk/test/api/hotswap/hotswap-deployments.test.ts

@@ -356,3 +356,61 @@ test('changing the type of a deployed resource always results in a full deployme
   expect(mockUpdateMachineDefinition).not.toHaveBeenCalled();
   expect(mockUpdateLambdaCode).not.toHaveBeenCalled();
 });
+
+test('A change to both a hotswappable resource and a stack output results in a full deployment', async () => {
+  // GIVEN
+  setup.setCurrentCfnStackTemplate({
+    Resources: {
+      Func: {
+        Type: 'AWS::Lambda::Function',
+        Properties: {
+          Code: {
+            S3Bucket: 'current-bucket',
+            S3Key: 'current-key',
+          },
+          FunctionName: 'my-function',
+        },
+        Metadata: {
+          'aws:asset:path': 'old-path',
+        },
+      },
+    },
+    Outputs: {
+      SomeOutput: {
+        Value: 'old-value',
+      },
+    },
+  });
+  const cdkStackArtifact = setup.cdkStackArtifactOf({
+    template: {
+      Resources: {
+        Func: {
+          Type: 'AWS::Lambda::Function',
+          Properties: {
+            Code: {
+              S3Bucket: 'current-bucket',
+              S3Key: 'new-key',
+            },
+            FunctionName: 'my-function',
+          },
+          Metadata: {
+            'aws:asset:path': 'new-path',
+          },
+        },
+      },
+      Outputs: {
+        SomeOutput: {
+          Value: 'new-value',
+        },
+      },
+    },
+  });
+
+  // WHEN
+  const deployStackResult = await hotswapMockSdkProvider.tryHotswapDeployment(cdkStackArtifact);
+
+  // THEN
+  expect(deployStackResult).toBeUndefined();
+  expect(mockUpdateMachineDefinition).not.toHaveBeenCalled();
+  expect(mockUpdateLambdaCode).not.toHaveBeenCalled();
+});