(aws-stepfunctions): JsonPath doest not accept strings starting with $[

[marciocadev]

Describe the bug

When going through a parallel task, the result is an array and to work with it, it needs to be referenced through strings starting with $[

Expected Behavior

Make the JsonPath.listAt function able to process strings starting with $[

Current Behavior

When trying to process a task with the JsonPath.listAt function after a parallel task we get the following error

Error: Data JSON path values must either be exactly equal to '$' or start with '$.'
    at validateDataPath (/home/marcio/marcio/stepfunctions-dynamodb-playground/node_modules/aws-cdk-lib/aws-stepfunctions/lib/fields.js:1:4081)
    at Function.listAt (/home/marcio/marcio/stepfunctions-dynamodb-playground/node_modules/aws-cdk-lib/aws-stepfunctions/lib/fields.js:1:434)

Reproduction Steps

This error can be seen when trying to insert a string set into DynamoDB where the initial input went through a parallel task

const table = new ddb.Table(this, 'Table', {
  partitionKey: { name: 'pk', type: ddb.AttributeType.STRING },
  removalPolicy: cdk.RemovalPolicy.DESTROY,
});

const passPK = new sfn.Pass(this, 'passPK', {
  parameters: { 'pk.$': '$.pk' },
});
const passStringSet = new sfn.Pass(this, 'PassStringSet', {
  parameters: { 'stringset.$': '$.stringset' },
});

const parallel = new sfn.Parallel(this, 'Parallel', {
  resultPath: '$',
});
parallel.branch(passPK)
  .branch(passStringSet);

const putItem = new tasks.DynamoPutItem(this, 'PutItem', {
  table: table,
  item: {
    pk: tasks.DynamoAttributeValue.fromString('$[0].pk'),
    stringset: tasks.DynamoAttributeValue.fromStringSet(sfn.JsonPath.listAt('$[1].stringset')),
  },
});

const definition = sfn.Chain.start(parallel).next(putItem);

new sfn.StateMachine(this, 'StateMachine', {
  definition: definition,
});

Possible Solution

add the possibility for the JsonPath.listAt function to process strings starting with $[

Additional Information/Context

No response

CDK CLI Version

2.45.0

Framework Version

No response

Node.js Version

v18.10.0

OS

Linux

Language

Typescript

Language Version

No response

Other information

No response

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