aws-stepfunctions: state.Retry is not iterable

[abdelnn]

Describe the bug

When creating a CustomState within a state machine, and specifying the retry behaviour within the inline definition, we get back an error saying state.Retry is not iterable. However, adding the retry behaviour separately with .addRetry seems to fix this issue. I strongly suspects this is linked to the following PR #28793

Expected Behavior

The state machine should create successfully

Current Behavior

Throws

TypeError: state.Retry is not iterable
    at CustomState.toStateJson

Reproduction Steps

Creating a state machine with the following state

const myLambdaState: sfn.CustomState = new sfn.CustomState(this, 'Call Lambda', {
            stateJson: {
                Type: "Task",
                Resource: "arn:aws:states:::lambda:invoke",
                OutputPath: "$.Payload",
                Parameters: {
                    'Payload.$': "$",
                    "FunctionName": "arn:aws:lambda:us-east-1:<<ACCOUNT>>:function:print1:$LATEST"
                },
                Retry: [
                    {
                        "ErrorEquals": [
                            "Lambda.ServiceException",
                            "Lambda.AWSLambdaException",
                            "Lambda.SdkClientException",
                            "Lambda.TooManyRequestsException"
                        ],
                        "IntervalSeconds": 1,
                        "MaxAttempts": 3,
                        "BackoffRate": 2
                    }
                ],
                Catch: [
                    {
                        ErrorEquals: [
                            "States.ALL"
                        ],
                        Next: "fail.id"
                    }
                ]
                ,
            }
        });

However, doing the following works:

      const success: sfn.Succeed = new sfn.Succeed(this, 'Success Name');
        const fail: sfn.Fail = new sfn.Fail(this, 'Fail Name');

        const myLambdaState: sfn.CustomState = new sfn.CustomState(this, 'Call Lambda', {
            stateJson: {
                Type: "Task",
                Resource: "arn:aws:states:::lambda:invoke",
                OutputPath: "$.Payload",
                Parameters: {
                    'Payload.$': "$",
                    "FunctionName": "arn:aws:lambda:us-east-1:<<ACCOUNT-ID>>:function:print1:$LATEST"
                }
            }
        });
        myLambdaState.addRetry({
            maxAttempts: 1,
            maxDelay: cdk.Duration.seconds(5),
            jitterStrategy: sfn.JitterType.FULL,
        });

        myLambdaState.addCatch(fail, {
            errors: ['States.ALL']
        }
        )
        myLambdaState.next(success);

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.128.0

Framework Version

No response

Node.js Version

v21.6.2

OS

Mac 14.3.1

Language

TypeScript

Language Version

No response

Other information

No response

[jsayres]

The problem seems to be here: https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/aws-stepfunctions/lib/states/custom-state.ts#L74

renderRetryCatch can yield a value of undefined for Retry if the list of retries is empty. You can see this in the renderList function: https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/aws-stepfunctions/lib/states/state.ts#L641

This will cause the state value to have a Retry of undefined from the merge. Then the attempt to iterate fails here: https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/aws-stepfunctions/lib/states/custom-state.ts#L79

The solution would be to make the merge a bit smarter and also to validate state.Retry.

[abdelnn]

I agree - which is probably why we're not getting an error when specifying the error strategy through .addRetry

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[abhi-shek01]

In which file do we need to make this change? I am getting a same error with "aws-cdk-lib" : "^2.118.0" version @abdelnn

[wong-a]

@abhi-shek01 The fix was released in the most recent version of aws-cdk https://github.com/aws/aws-cdk/releases/tag/v2.133.0