(core): CfnOutput does not validate export name during synthesis but can fail during deployment

[The-Zona-Zoo]

Describe the bug

It is possible to create a CfnOutput in the CDK that synthesizes without issue, but then fails to deploy due to an invalid export name.

Expected Behavior

The CfnOutput exportName property should be validated according to the cloud formation rules at synthesis time to catch this problem sooner in the process.

Current Behavior

CDK synthesis works just fine, however during deployment Cloud Formation deployments will fail:

Deployment failed: Error [ValidationError]: Template format error: Output <SomeOutputNameHere> is malformed. The Name field of every Export member must be specified and consist only of alphanumeric characters, colons, or hyphens.

Reproduction Steps

import { CfnOutput, Stack } from 'aws-cdk-lib';

export class MyStack extends Stack {
  constructor(...props: ConstructorParameters<typeof Stack>) {
    super(...props);

    new CfnOutput(this, 'id', {
      value: 'SomeValue',
      exportName: 'SOME_INVALID_EXPORT_NAME`,
    });
  }
}

Possible Solution

Validate the exportName field of the CfnOutput constructor props during synthesis. Possibly via a regex similar to [A-Za-z\d\-\:]*.

Additional Information/Context

I filed this under bug even though there isn't anything technically "wrong" with the CDK code because as a user, I would expect the synthesis to fail if something that can be validated to conform to cloud formation rules can be validated at synthesis time (and indeed in this case it appears at least on the surface that it can be).

CDK CLI Version

2.114.1

Framework Version

No response

Node.js Version

18

OS

MacOS 14 + Amazon Linux 2 5.10

Language

TypeScript

Language Version

5

Other information

No response

[pahud]

Yes we definitely should validate it in CDK. Thanks for the report and we welcome PRs from the community.

[github-actions]

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