(aws_apigateway): empty policy attribute for CfnRestApi fails synthesize

[jwoehrle]

Describe the bug

I'm playing with cdk migrate and came across an IMO general CDK issue.
The following CloudFormation Resource deploys just fine:

"ApiGatewayRestApi": {
      "Type": "AWS::ApiGateway::RestApi",
      "Properties": {
        "Name": "serverless-project-dev",
        "EndpointConfiguration": {
          "Types": [
            "EDGE"
          ]
        },
        "Policy": "",
        "MinimumCompressionSize": 1024
      }
    },

Note the empty string for the Policy attribute

Migrated into CDK with cdk migrate this results in the following L1 construct:

    const apiGatewayRestApi = new apigateway.CfnRestApi(this, 'ApiGatewayRestApi', {
      name: 'serverless-project-dev',
      endpointConfiguration: {
        types: [
          'EDGE',
        ],
      },
      policy: '',
      minimumCompressionSize: 1024,
    });

which fails synthesis with the following error:

CfnSynthesisError: Resolution error: Supplied properties not correct for "CfnRestApiProps"
policy: "" should be an 'object'.

When I remove the policy key completely synthesis succeeds

Expected Behavior

L1 constructs should behave like CFN and therefore an empty string as policy value should succeed

Current Behavior

cdk synth fails

Reproduction Steps

try to deploy a CfnRestApi with empty string as value for policy attribute

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.128.0 (build d995261)

Framework Version

No response

Node.js Version

v20.9.0

OS

macOS

Language

TypeScript

Language Version

TypeScript (~5.3.3)

Other information

No response

[pahud]

Thank you for the report. We'll bring this up to the maintainer for further investigation.

[TheRealAmazonKendra]

As this is a problem across our L1s and is not specific to CDK migrate, I'm un-assigning myself on this. I am curious, however, if we accept an empty string for L2s here.

[moelasmar]

I believe this is a CFN schema issue. Policy attribute is of type JSON as per CFN docs, but it accepts an empty string as a valid JSON which is not correct, so if string is an accepted type, so I believe this should be reflected in the CFN schema of the "AWS::ApiGateway::RestApi" resource.

Also, I do not think this is a P1 issue as the empty string policy is actually handled the same as null.