Tracking Issue: Fn::ToJsonString RFC

[mluk-aws]

Description

Provide an intrinsic function that converts an input template block into an escaped JSON string.

Original Issue: #53

Workflow

• Tracking issue created (label: status/proposed)
• RFC pull request submitted
• Reviewers assigned (label: status/review)
• Reviewers signed-off (label approved applied to pull request)
• Final comments period (label: status/final-comments-period)
• Approved and merged (label: status/approved)
• Implementation started (label: status/implementing)
• Implementation complete (label: status/done)

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Author is responsible to progress the RFC according to this checklist, and
apply the relevant labels to this issue so that the RFC table in README gets
updated.

[jiemying]

Hi have cases say it is not working at the moment

  EventPattern:
    Fn::ToJsonString:
      - test1: 'test2'
        test3: 'test4'

Stack will fail at the Transform stage with error "Transform AWS::LanguageExtensions failed with: Fn::ToJsonString resolve value type mismatch. Rollback requested by user."

[MalikAtalla-AWS]

Hey @jiemying,
thanks for bringing this up.

To unblock you: EventPattern supports Json objects natively. There is no need to use Fn::ToJsonString for the EventPattern attribute.

[jiemying]

Hey @jiemying, thanks for bringing this up.

To unblock you: EventPattern supports Json objects natively. There is no need to use Fn::ToJsonString for the EventPattern attribute.

Hi, thx for coming back to me so promptly!

Yep I am aware of that, that was for reference.

The error happens at the Transform stage of the CloudFormation stack operation, no matter where I put the above test Fn::ToJsonString in the template's resources properties, the stack transform stage failed with the same error.

I suspect the object "type" passed to this intrinsic function in the back-end, does not match wanted object type of the code, hence the exception error throws. Look at the exception part of the code may be helpful.

[MalikAtalla-AWS]

Hey @jiemying,
if this happens even when you put Fn::ToJsonString somewhere else (where a String is expected), I would appreciate if you could provide an example template. If you still have it handy, any chance you could open a new issue in this same repo?

[lejiati]

Close this issue as it's available via AWS::LanguageExtensions