(CLI): The DefaultStackSynthesizer executes change sets for no-op nested stacks

[donkersgoed-postnl]

What is the problem?

In an environment with nested stacks, two subsequent deploys without changes between them result in a full (slow) deployment. This has been solved for the LegacyStackSynthesizer (see #6346 and #6046), but the issue is present again with the DefaultStackSynthesizer.

Reproduction Steps

Using the DefaultStackSynthesizer create a stack with nested stacks and run a cdk deploy.

What did you expect to happen?

No deployment and the following (verbose) output:

luc-IntegrationTestDev: checking if we can skip deploy
luc-IntegrationTestDev: skipping deployment (use --force to override)

 ✅  IntegrationTestCdkStack (luc-IntegrationTestDev) (no changes)

What actually happened?

A changeset is created and executed.

CDK CLI Version

1.122.0

Framework Version

No response

Node.js Version

v16.8.0

OS

MacOS 10.15.7 (19H1419)

Language

Python

Language Version

Python (3.8.12)

Other information

When I use the LegacyStackSynthesizer on the same code base, the results are as expected. When I switch to the DefaultStackSynthesizer, I get the results described above.

[rix0rrr]

Interesting. Can you run cdk deploy -v and note the reason?

In case it is template has changed, can you then try:

$ aws cloudformation get-template --stack-name YOURSTACK > cfntemplate.json
$ diff cfntemplate.json cdk.out/YOURSTACK.template.json

And tell me what the differences are?

[donkersgoed-postnl]

A bit of background: these are two stacks that are being deployed together with cdk deploy --all --require-approval never -v. The deployment runs in GitHub Actions, so the container it runs in is replaced with every deploy.

The first stack has nested stacks, the second doesn't. The second stack uses exported values from the first.

The second stack detects no changes.

The first stack is always redeployed, this is the GitHub Actions workflow:

      - name: CDK Synth
        run: |
          cdk synth -q
      - name: Run EBE diff
        continue-on-error: true
        run: |
          aws cloudformation get-template --stack-name github-EventBrokerEcommerceDev --query 'TemplateBody' | jq -r > cfntemplate.json
          cat cdk.out/EbeBackendCdkStack.template.json | jq -r > local_template.json       
          diff cfntemplate.json local_template.json
      - name: Run IntegrationTest diff
        continue-on-error: true
        run: |
          aws cloudformation get-template --stack-name github-IntegrationTestDev --query 'TemplateBody' | jq -r > cfntemplate.json
          cat cdk.out/IntegrationTestCdkStack.template.json | jq -r > local_template.json
          diff cfntemplate.json local_template.json
      # Perform the deployment
      - name: Deploy EBE and latest integration tests
        run: |
          cdk deploy --all --require-approval never -v

Both the diffs give no output and exit code 0 (so there is no diff). But in the next step, it starts to deploy:

github-EventBrokerEcommerceDev: checking if we can skip deploy
github-EventBrokerEcommerceDev: parameters have changed
github-EventBrokerEcommerceDev: deploying...

[rix0rrr]

github-EventBrokerEcommerceDev: parameters have changed

Iiiiiiiiiiiii see. Thanks!

[github-actions]

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