core(cli): hotswap to be more tolerant of the Fn::ImportValue usage #21320
Description
Describe the feature
The CDK CLI will refuse to hotswap a resource if its definition contains the intrinsic function Fn::Import.
Could not perform a hotswap deployment, because the CloudFormation template could not be resolved: CloudFormation function Fn::ImportValue is not supported
This is because the hotswap feature needs the template to be fully resolved in order to correctly determine the changes; and Fn::ImportValue is not supported by CDK's resolver function.
The hotswap feature should be more tolerant of the Fn::ImportValue usage. It should accept the case where Fn::ImportValue is use and the import name has not changed. This is the case where we can safely assume that the value will not change (thanks to CloudFormation's protection around exported/imported names). To be more specific on the expected behavior:
- If the imported value needs to be used in the request of the hotswap operation, CDK should try to fetch the value
- If the imported value does not need to be in the request, CDK can just ignore it.
Use Case
Fn::ImportValue is commonly used by CDK applications. Some users may be using it without knowing it. But as soon as their template uses this intrinsic function, hotswap will stop working.
Proposed Solution
No response
Other Information
No response
Acknowledgements
- I may be able to implement this feature request
- This feature might incur a breaking change
CDK version used
2.33.0 (build 859272d)
Environment details (OS name and version, etc.)
Darwin Kernel Version 21.6.0