CDK to CFN template is serializing incorrectly

[srivastavr]

Name of the resource

AWS::StepFunctions::StateMachine

Resource Name

No response

Issue Description

Hi,

We are passing array of array in payload from step function to a lambda function, below is the sample code

            lambdaFunction: serviceCallHandler,
            resultSelector: resultSelector,
            resultPath: resultPath,
            payload: TaskInput.fromObject({
                key1: [
                    [
                        {
                            key2: {
                                key3: 'value1',
                            },
                            key4: [
                                [
                                    {
                                        key5: {
                                            key6: 'value2',
                                        },
                                    },
                                ],
                            ],
                        },
                    ],
                ],
            }),
        }

but after building, the cloud formation template converts this into array of objects with 0 index at places which is incorrect.

like this

 {
        "Ref": "AWS::Partition"
       },
       ":states:::lambda:invoke\",\"Parameters\":{\"FunctionName\":\"",
       {
        "Fn::GetAtt": [
         "servicecallhandler3F6E12B2",
         "Arn"
        ]
       },
       "\",\"Payload\":{\"key1\":[{\"0\":{\"key2\":{\"key3\":\"value1\"},\"key4\":[{\"0\":{\"key5\":{\"key6\":\"value2\"}}}]}}]}}}

Expected Behavior

 {
        "Ref": "AWS::Partition"
       },
       ":states:::lambda:invoke\",\"Parameters\":{\"FunctionName\":\"",
       {
        "Fn::GetAtt": [
         "servicecallhandler3F6E12B2",
         "Arn"
        ]
       },
       "\",\"Payload\":{\"key1\":[[{\"key2\":{\"key3\":\"value1\"},\"key4\":[[{\"key5\":{\"key6\":\"value2\"}]}]}}]]}}

Observed Behavior

{
        "Ref": "AWS::Partition"
       },
       ":states:::lambda:invoke\",\"Parameters\":{\"FunctionName\":\"",
       {
        "Fn::GetAtt": [
         "servicecallhandler3F6E12B2",
         "Arn"
        ]
       },
       "\",\"Payload\":{\"key1\":[{\"0\":{\"key2\":{\"key3\":\"value1\"},\"key4\":[{\"0\":{\"key5\":{\"key6\":\"value2\"}}}]}}]}}}

Test Cases

NA

Other Details

No response

[benbridts]

@srivastavr You might want to report this in the CDK repository, this doesn't look like a bug on the CloudFormation side.

See https://github.com/aws/aws-cdk#getting-help

[evscott]

Like @benbridts said, this doesn't look like a bug in CloudFormation, the serialization is implemented in CDK:

https://github.com/aws/aws-cdk/blob/a79794e3f2609e6efa5cf659eec039964a8ad61c/packages/aws-cdk-lib/aws-stepfunctions/lib/input.ts#L21-L23

It also doesn't look like the issue is in Step Functions' TaskInput class: https://www.mycompiler.io/view/ATeYKGae0NT

[srivastavr]

Opened a issue at CDK(aws/aws-cdk#26111)

Thanks