fix: prevent cyclic dependencies created by custom resource provider

[swachter]

Reason for this change

If both, the isCompleteHandler and the role is set in custom resource ProviderProps then a resource dependencies cycle results.

If role is specified then that role is used for all 3 framework lambdas (i.e. onEventFunction, isCompleteFunction, and timeoutFunction). In order to grant additional required permissions to these functions, a policy is created under the hood. That policy is called DefaultPolicy.

The DefaultPolicy is attached to the given role and includes the lambda:InvokeFunction permissions for the two handler functions (onEventHandler and isCompleteHandler). In addition, the DefaultPolicy includes the states:StartExecution permission that is granted to the onEventFunction by the call `waiterStateMachine.grantStartExecution(onEventFunction);.

This results in the following dependencies cycle:

waiter state machine --(via its description)--> isCompleteFunction / timeoutFunction --(via explicits dependsOn)--> DefaultPolicy --(via resource constraint)--> waiter state machine

If the resource constraint is dropped from the states:StartExecution grant then the cyclic dependency is cut.

Description of changes

Drop the resource constraint from the states:StartExecution grant if an execution role for the framework lambdas is specified.

Description of how you validated changes

I tried the following workaround locally:

(role as any).node._children.DefaultPolicy.document.statements[1] = new PolicyStatement({
    actions: ['states:StartExecution'],
    resources: ['*']
});

This workaround applies the proposed modification to the created DefaultPolicy.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

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

[aws-cdk-automation]

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[swachter]

Clarification Request

There seems to exist no integration test for custom resource providers.

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 763b0f2
• Result: SUCCEEDED
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[swachter]

Exemption Request
There seem to be no integration tests for custom resource providers.

[aws-cdk-automation]

The pull request linter fails with the following errors:

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[GavinZZ]

Hello, thanks for drafting this PR. I'd like to understand what issue were you seeing prior to this change. Is the cyclic dependency causing the deployment to fail?

[StefanWachter1507]

Yes, the deployment fails with a cyclic dependency error.

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This PR has been deemed to be abandoned, and will be automatically closed. Please create a new PR for these changes if you think this decision has been made in error.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.63%. Comparing base (c78ef1b) to head (763b0f2).
Report is 367 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #32404       +/-   ##
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- Coverage   78.66%   66.63%   -12.03%     
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  Files         107      332      +225     
  Lines        7237    18965    +11728     
  Branches     1329     3301     +1972     
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+ Hits         5693    12638     +6945     
- Misses       1358     6001     +4643     
- Partials      186      326      +140     

Flag	Coverage Δ
suite.unit	66.63% <ø> (-12.03%)	⬇️

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Components	Coverage Δ
packages/aws-cdk	79.92% <ø> (+1.25%)	⬆️

[GavinZZ]

Thanks for the quick response. I think this is a great place to add an integ test to make sure now it's deployable if we supply a custom role property. The provider module doesn't have integ test directly because it's usually coupled with other modules that use the custom resource provider. I'd like to request to add an integ test if you can and feel free to ping me if you need help with the integ test.

[StefanWachter1507]

Unfortunately, I have no clue how an integration test for a custom resource provider could be set up. I would appreciate your help a lot.

[aws-cdk-automation]

This PR has been deemed to be abandoned, and will be automatically closed. Please create a new PR for these changes if you think this decision has been made in error.

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